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docs: Update startService() & bindService() documentation (Proj13)

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Change-Id: I976128eb4c14ee2587c9cfa9c34f4b3dc006aa38
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George French
2016-10-25 00:19:33 +00:00
committed by android-build-merger
parent 8233c03d1e 9748d76be9
commit e8e196d007
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docs/html/google/play/billing/billing_integrate.jd
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@@ -9,18 +9,18 @@ page.tags="inapp, billing, iap"
<h2>In this document</h2>
<ol>
<li><a href="#billing-add-aidl">Adding the AIDL file</a></li>
<li><a href="#billing-permission">Updating Your Manifest</a></li>
<li><a href="#billing-permission">Updating your manifest</a></li>
<li><a href="#billing-service">Creating a ServiceConnection</a></li>
<li><a href="#billing-requests">Making In-app Billing Requests</a>
<li><a href="#billing-requests">Making In-app Billing requests</a>
<ol>
<li><a href="#QueryDetails">Querying Items Available for Purchase</a><li>
<li><a href="#Purchase">Purchasing an Item</a></li>
<li><a href="#QueryPurchases">Querying Purchased Items</a></li>
<li><a href="#Consume">Consuming a Purchase</a></li>
<li><a href="#Subs">Implementing Subscriptions</a></li>
<li><a href="#QueryDetails">Querying items available for purchase</a><li>
<li><a href="#Purchase">Purchasing an item</a></li>
<li><a href="#QueryPurchases">Querying purchased items</a></li>
<li><a href="#Consume">Consuming a purchase</a></li>
<li><a href="#Subs">Implementing subscriptions</a></li>
</ol>
</li>
<li><a href="#billing-security">Securing Your App</a>
<li><a href="#billing-security">Securing your app</a>
</ol>
<h2>Reference</h2>
<ol>
@@ -42,7 +42,7 @@ page.tags="inapp, billing, iap"
In-app Billing on Google Play provides a straightforward, simple interface
for sending In-app Billing requests and managing In-app Billing transactions
using Google Play. The information below covers the basics of how to make
calls from your application to the In-app Billing service using the Version 3
calls from your application to the In-app Billing service using the In-app Billing Version 3
API.
</p>
@@ -51,26 +51,25 @@ page.tags="inapp, billing, iap"
your application, see the <a href=
"{@docRoot}training/in-app-billing/index.html">Selling In-app Products</a>
training class. The training class provides a complete sample In-app Billing
application, including convenience classes to handle key tasks related to
setting up your connection, sending billing requests and processing responses
application, including convenience classes to handle key tasks that are related to
setting up your connection, sending billing requests, processing responses
from Google Play, and managing background threading so that you can make
In-app Billing calls from your main activity.
</p>
<p>
Before you start, be sure that you read the <a href=
Before you start, read the <a href=
"{@docRoot}google/play/billing/billing_overview.html">In-app Billing
Overview</a> to familiarize yourself with concepts that will make it easier
Overview</a> to familiarize yourself with concepts that make it easier
for you to implement In-app Billing.
</p>
<p>To implement In-app Billing in your application, you need to do the
following:</p>
<p>Complete these steps to implement In-app Billing in your application:</p>
<ol>
<li>Add the In-app Billing library to your project.</li>
<li>Update your {@code AndroidManifest.xml} file.</li>
<li>Create a {@code ServiceConnection} and bind it to
<li>Create a {@code ServiceConnection} and bind it to the
{@code IInAppBillingService}.</li>
<li>Send In-app Billing requests from your application to
{@code IInAppBillingService}.</li>
@@ -79,55 +78,56 @@ following:</p>
<h2 id="billing-add-aidl">Adding the AIDL file to your project</h2>
<p>{@code IInAppBillingService.aidl} is an Android Interface Definition
<p>The {@code IInAppBillingService.aidl} is an Android Interface Definition
Language (AIDL) file that defines the interface to the In-app Billing Version
3 service. You will use this interface to make billing requests by invoking IPC
3 service. You can use this interface to make billing requests by invoking IPC
method calls.</p>
<p>To get the AIDL file:</p>
<p>Complete these steps to get the AIDL file:</p>
<ol>
<li>Open the <a href="{@docRoot}tools/help/sdk-manager.html">Android SDK Manager</a>.</li>
<li>In the SDK Manager, expand the {@code Extras} section.</li>
<li>Select <strong>Google Play Billing Library</strong>.</li>
<li>Click <strong>Install packages</strong> to complete the download.</li>
</ol>
<p>The {@code IInAppBillingService.aidl} file will be installed to {@code <sdk>/extras/google/play_billing/}.</p>
<p>The {@code IInAppBillingService.aidl} file will be installed to {@code &lt;sdk&gt;/extras/google/play_billing/}.</p>
<p>To add the AIDL to your project:</p>
<p>Complete these steps to add the AIDL to your project:</p>
<ol>
<li>First, download the Google Play Billing Library to your Android project:
<li>Download the Google Play Billing Library to your Android project:
<ol type="a">
<li>Select <strong>Tools > Android > SDK Manager</strong>.</li>
<li>Under <strong>Appearance & Behavior > System Settings > Android SDK</strong>,
select the <em>SDK Tools</em> tab to select and download <em>Google Play Billing
Library</em>.</li></ol>
<li>Next, copy the {@code IInAppBillingService.aidl} file to your project.
<li>Copy the {@code IInAppBillingService.aidl} file to your project.
<ul>
<li>If you are using Android Studio:
<li>If you are using Android Studio, complete these steps to copy the file:
<ol type="a">
<li>Navigate to {@code src/main} in the Project tool window.</li>
<li>Select <strong>File > New > Directory</strong> and enter {@code aidl} in the
<em>New Directory</em> window, then select <strong>OK</strong>.
<li>Select <strong>File > New > Directory</strong>, enter {@code aidl} in the
<em>New Directory</em> window, and select <strong>OK</strong>.
<li>Select <strong>File > New > Package</strong> and enter
{@code com.android.vending.billing} in the <em>New Package</em> window, then select
<li>Select <strong>File > New > Package</strong>, enter
{@code com.android.vending.billing} in the <em>New Package</em> window, and select
<strong>OK</strong>.</li>
<li>Using your operating system file explorer, navigate to
{@code <sdk>/extras/google/play_billing/}, copy the
{@code &lt;sdk&gt;/extras/google/play_billing/}, copy the
{@code IInAppBillingService.aidl} file, and paste it into the
{@code com.android.vending.billing} package in your project.
</li>
</ol>
</li>
<li>If you are developing in a non-Android Studio environment: Create the
following directory {@code /src/com/android/vending/billing} and copy the
{@code IInAppBillingService.aidl} file into this directory. Put the AIDL
file into your project and use the Gradle tool to build your project so that
the <code>IInAppBillingService.java</code> file gets generated.
<li>If you are developing in a non-Android Studio environment, create the
following directory: {@code /src/com/android/vending/billing}. Copy the
{@code IInAppBillingService.aidl} file into this directory. Place the AIDL
file in your project and use the Gradle tool to build your project so that
the <code>IInAppBillingService.java</code> file is generated.
</li>
</ul>
</li>
@@ -137,16 +137,16 @@ method calls.</p>
</li>
</ol>
<h2 id="billing-permission">Updating Your App's Manifest</h2>
<h2 id="billing-permission">Updating your app's manifest</h2>
<p>
In-app billing relies on the Google Play application, which handles all
communication between your application and the Google Play server. To use the
of the communication between your application and the Google Play server. To use the
Google Play application, your application must request the proper permission.
You can do this by adding the {@code com.android.vending.BILLING} permission
to your AndroidManifest.xml file. If your application does not declare the
In-app Billing permission, but attempts to send billing requests, Google Play
will refuse the requests and respond with an error.
refuses the requests and responds with an error.
</p>
<p>
@@ -182,7 +182,7 @@ method calls.</p>
onServiceDisconnected} and {@link
android.content.ServiceConnection#onServiceConnected onServiceConnected}
methods to get a reference to the {@code IInAppBillingService} instance after
a connection has been established.
a connection is established.
</p>
<pre>
@@ -208,20 +208,25 @@ ServiceConnection mServiceConn = new ServiceConnection() {
bindService} method. Pass the method an {@link android.content.Intent} that
references the In-app Billing service and an instance of the {@link
android.content.ServiceConnection} that you created, and explicitly set the
Intent's target package name to <code>com.android.vending</code> — the
Intent's target package name to <code>com.android.vending</code>&mdash;the
package name of Google Play app.
</p>
<p class="caution">
<strong>Caution:</strong> To protect the security of billing transactions,
always make sure to explicitly set the intent's target package name to
always explicitly set the intent's target package name to
<code>com.android.vending</code>, using {@link
android.content.Intent#setPackage(java.lang.String) setPackage()} as shown in
the example below. Setting the package name explicitly ensures that
android.content.Intent#setPackage(java.lang.String) setPackage()}.
Setting the package name explicitly ensures that
<em>only</em> the Google Play app can handle billing requests from your app,
preventing other apps from intercepting those requests.
</p>
<p>
The following code sample demonstrates how to set the intent's target package
to protect the security of transactions:
</p>
<pre>&#64;Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
@@ -233,6 +238,13 @@ public void onCreate(Bundle savedInstanceState) {
}
</pre>
<p class="caution"><strong>Caution</strong>: To ensure that your app is secure, always use an
explicit intent when starting a {@link android.app.Service} and do not declare intent filters for
your services. Using an implicit intent to start a service is a security hazard because you cannot
be certain of the service that will respond to the intent, and the user cannot see which service
starts. Beginning with Android 5.0 (API level 21), the system throws an exception if you call
{@link android.content.Context#bindService bindService()} with an implicit intent.</p>
<p>
You can now use the mService reference to communicate with the Google Play
service.
@@ -242,10 +254,14 @@ public void onCreate(Bundle savedInstanceState) {
<strong>Important:</strong> Remember to unbind from the In-app Billing
service when you are done with your {@link android.app.Activity}. If you
don’t unbind, the open service connection could cause your device’s
performance to degrade. This example shows how to perform the unbind
performance to degrade.
</p>
<p>
This example shows how to perform the unbind
operation on a service connection to In-app Billing called {@code
mServiceConn} by overriding the activity’s {@link
android.app.Activity#onDestroy onDestroy} method.
android.app.Activity#onDestroy onDestroy} method:
</p>
<pre>
@@ -264,29 +280,29 @@ public void onDestroy() {
"{@docRoot}training/in-app-billing/preparing-iab-app.html">Selling In-app
Products</a> training class and associated sample.
</p>
<h2 id="billing-requests">Making In-app Billing Requests</h2>
<h2 id="billing-requests">Making In-app Billing requests</h2>
<p>
Once your application is connected to Google Play, you can initiate purchase
After your application is connected to Google Play, you can initiate purchase
requests for in-app products. Google Play provides a checkout interface for
users to enter their payment method, so your application does not need to
users to enter their payment method, so your application doesn't need to
handle payment transactions directly. When an item is purchased, Google Play
recognizes that the user has ownership of that item and prevents the user
from purchasing another item with the same product ID until it is consumed.
You can control how the item is consumed in your application, and notify
You can control how the item is consumed in your application and notify
Google Play to make the item available for purchase again. You can also query
Google Play to quickly retrieve the list of purchases that were made by the
user. This is useful, for example, when you want to restore the user's
Google Play to quickly retrieve the list of purchases that the
user made. This is useful, for example, when you want to restore the user's
purchases when your user launches your app.
</p>
<h3 id="QueryDetails">Querying for Items Available for Purchase</h3>
<h3 id="QueryDetails">Querying for items available for purchase</h3>
<p>
In your application, you can query the item details from Google Play using
the In-app Billing Version 3 API. To pass a request to the In-app Billing
service, first create a {@link android.os.Bundle} that contains a String
service, create a {@link android.os.Bundle} that contains a String
{@link java.util.ArrayList} of product IDs with key "ITEM_ID_LIST", where
each string is a product ID for an purchasable item.
each string is a product ID for an purchasable item. Here is an example:
</p>
<pre>
@@ -299,9 +315,9 @@ querySkus.putStringArrayList(“ITEM_ID_LIST”, skuList);
<p>
To retrieve this information from Google Play, call the {@code getSkuDetails}
method on the In-app Billing Version 3 API, and pass the method the In-app
method on the In-app Billing Version 3 API and pass the In-app
Billing API version (“3”), the package name of your calling app, the purchase
type (“inapp”), and the {@link android.os.Bundle} that you created.
type (“inapp”), and the {@link android.os.Bundle} that you created, into the method:
</p>
<pre>
@@ -310,35 +326,35 @@ Bundle skuDetails = mService.getSkuDetails(3,
</pre>
<p>
If the request is successful, the returned {@link android.os.Bundle}has a
If the request is successful, the returned {@link android.os.Bundle} has a
response code of {@code BILLING_RESPONSE_RESULT_OK} (0).
</p>
<p class="note">
<strong>Warning:</strong> Do not call the {@code getSkuDetails} method on the
main thread. Calling this method triggers a network request which could block
<strong>Warning:</strong> Don't call the {@code getSkuDetails} method on the
main thread. Calling this method triggers a network request that could block
your main thread. Instead, create a separate thread and call the {@code
getSkuDetails} method from inside that thread.
getSkuDetails} method from inside of that thread.
</p>
<p>
To see all the possible response codes from Google Play, see <a href=
To view all of the possible response codes from Google Play, see <a href=
"{@docRoot}google/play/billing/billing_reference.html#billing-codes">In-app
Billing Reference</a>.
</p>
<p>
The query results are stored in a String ArrayList with key {@code
DETAILS_LIST}. The purchase information is stored in the String in JSON
format. To see the types of product detail information that are returned, see
DETAILS_LIST}. The purchase information is stored within the String in JSON
format. To view the types of product detail information that are returned, see
<a href=
"{@docRoot}google/play/billing/billing_reference.html#getSkuDetails">In-app
Billing Reference</a>.
</p>
<p>
In this example, you are retrieving the prices for your in-app items from the
skuDetails {@link android.os.Bundle} returned from the previous code snippet.
In this example shows how to retrieve the prices for your in-app items from the
skuDetails {@link android.os.Bundle} that is returned from the previous code snippet:
</p>
<pre>
@@ -357,15 +373,15 @@ if (response == 0) {
}
</pre>
<h3 id="Purchase">Purchasing an Item</h3>
<h3 id="Purchase">Purchasing an item</h3>
<p>
To start a purchase request from your app, call the {@code getBuyIntent}
method on the In-app Billing service. Pass in to the method the In-app
method on the In-app Billing service. Pass the In-app
Billing API version (“3”), the package name of your calling app, the product
ID for the item to purchase, the purchase type (“inapp” or "subs"), and a
{@code developerPayload} String. The {@code developerPayload} String is used
{@code developerPayload} String into the method. The {@code developerPayload} String is used
to specify any additional arguments that you want Google Play to send back
along with the purchase information.
along with the purchase information. Here is an example:
</p>
<pre>
@@ -377,10 +393,13 @@ Bundle buyIntentBundle = mService.getBuyIntent(3, getPackageName(),
If the request is successful, the returned {@link android.os.Bundle} has a
response code of {@code BILLING_RESPONSE_RESULT_OK} (0) and a {@link
android.app.PendingIntent} that you can use to start the purchase flow. To
see all the possible response codes from Google Play, see <a href=
view all of the possible response codes from Google Play, see <a href=
"{@docRoot}google/play/billing/billing_reference.html#billing-codes">In-app
Billing Reference</a>. Next, extract a {@link android.app.PendingIntent} from
the response {@link android.os.Bundle} with key {@code BUY_INTENT}.
Billing Reference</a>.
<p>
The next step is to extract a {@link android.app.PendingIntent} from
the response {@link android.os.Bundle} with key {@code BUY_INTENT}, as shown here:
</p>
<pre>
@@ -390,8 +409,8 @@ PendingIntent pendingIntent = buyIntentBundle.getParcelable("BUY_INTENT");
<p>
To complete the purchase transaction, call the {@link
android.app.Activity#startIntentSenderForResult startIntentSenderForResult}
method and use the {@link android.app.PendingIntent} that you created. In
this example, you are using an arbitrary value of 1001 for the request code.
method and use the {@link android.app.PendingIntent} that you created. This
example uses an arbitrary value of 1001 for the request code:
</p>
<pre>
@@ -404,9 +423,9 @@ startIntentSenderForResult(pendingIntent.getIntentSender(),
Google Play sends a response to your {@link android.app.PendingIntent} to the
{@link android.app.Activity#onActivityResult onActivityResult} method of your
application. The {@link android.app.Activity#onActivityResult
onActivityResult} method will have a result code of {@code
Activity.RESULT_OK} (1) or {@code Activity.RESULT_CANCELED} (0). To see the
types of order information that is returned in the response {@link
onActivityResult} method has a result code of {@code
Activity.RESULT_OK} (1) or {@code Activity.RESULT_CANCELED} (0). To view the
types of order information that are returned in the response {@link
android.content.Intent}, see <a href=
"{@docRoot}google/play/billing/billing_reference.html#getBuyIntent">In-app
Billing Reference</a>.
@@ -415,7 +434,7 @@ startIntentSenderForResult(pendingIntent.getIntentSender(),
<p>
The purchase data for the order is a String in JSON format that is mapped to
the {@code INAPP_PURCHASE_DATA} key in the response {@link
android.content.Intent}, for example:
android.content.Intent}. Here is an example:
</p>
<pre>
@@ -436,13 +455,13 @@ startIntentSenderForResult(pendingIntent.getIntentSender(),
long. Pass this entire token to other methods, such as when you consume the
purchase, as described in <a href=
"{@docRoot}training/in-app-billing/purchase-iab-products.html#Consume">Consume
a Purchase</a>. Do not abbreviate or truncate this token; you must save and
a Purchase</a>. Don't abbreviate or truncate this token; you must save and
return the entire token.
</p>
<p>
Continuing from the previous example, you get the response code, purchase
data, and signature from the response {@link android.content.Intent}.
Continuing from the previous example, you receive the response code, purchase
data, and signature from the response {@link android.content.Intent}:
</p>
<pre>
@@ -472,23 +491,23 @@ protected void onActivityResult(int requestCode, int resultCode, Intent data) {
<p class="note">
<strong>Security Recommendation:</strong> When you send a purchase request,
create a String token that uniquely identifies this purchase request and
include this token in the {@code developerPayload}.You can use a randomly
generated string as the token. When you receive the purchase response from
Google Play, make sure to check the returned data signature, the {@code
include this token in the {@code developerPayload}. You can use a randomly-generated
string as the token. When you receive the purchase response from
Google Play, ensure that you check the returned data signature, the {@code
orderId}, and the {@code developerPayload} String. For added security, you
should perform the checking on your own secure server. Make sure to verify
should perform the checking on your own secure server. Verify
that the {@code orderId} is a unique value that you have not previously
processed, and the {@code developerPayload} String matches the token that you
processed and that the {@code developerPayload} String matches the token that you
sent previously with the purchase request.
</p>
<h3 id="QueryPurchases">Querying for Purchased Items</h3>
<h3 id="QueryPurchases">Querying for purchased items</h3>
<p>
To retrieve information about purchases made by a user from your app, call
To retrieve information about purchases that are made by a user from your app, call
the {@code getPurchases} method on the In-app Billing Version 3 service. Pass
in to the method the In-app Billing API version (“3”), the package name of
your calling app, and the purchase type (“inapp” or "subs").
the In-app Billing API version (“3”), the package name of
your calling app, and the purchase type (“inapp” or "subs") into the method. Here is an example:
</p>
<pre>
@@ -507,18 +526,18 @@ Bundle ownedItems = mService.getPurchases(3, getPackageName(), "inapp", null);
To improve performance, the In-app Billing service returns only up to 700
products that are owned by the user when {@code getPurchase} is first called.
If the user owns a large number of products, Google Play includes a String
token mapped to the key {@code INAPP_CONTINUATION_TOKEN} in the response
token that is mapped to the key {@code INAPP_CONTINUATION_TOKEN} in the response
{@link android.os.Bundle} to indicate that more products can be retrieved.
Your application can then make a subsequent {@code getPurchases} call, and
Your application can then make a subsequent {@code getPurchases} call and
pass in this token as an argument. Google Play continues to return a
continuation token in the response {@link android.os.Bundle} until all
products that are owned by the user has been sent to your app.
of the products that are owned by the user are sent to your app.
</p>
<p>For more information about the data returned by {@code getPurchases}, see
<p>For more information about the data that is returned by {@code getPurchases}, see
<a href="{@docRoot}google/play/billing/billing_reference.html#getPurchases">
In-app Billing Reference</a>. The following example shows how you can
retrieve this data from the response.
retrieve this data from the response:
</p>
<pre>
@@ -548,26 +567,26 @@ if (response == 0) {
</pre>
<h3 id="Consume">Consuming a Purchase</h3>
<h3 id="Consume">Consuming a purchase</h3>
<p>
You can use the In-app Billing Version 3 API to track the ownership of
purchased in-app products in Google Play. Once an in-app product is
purchased, it is considered to be "owned" and cannot be purchased from Google
purchased, it is considered to be <em>owned</em> and cannot be purchased from Google
Play. You must send a consumption request for the in-app product before
Google Play makes it available for purchase again.
</p>
<p class="caution">
<p class="note">
<strong>Important</strong>: Managed in-app products are consumable, but
subscriptions are not.
</p>
<p>
How you use the consumption mechanism in your app is up to you. Typically,
you would implement consumption for in-app products with temporary benefits
The way that you use the consumption mechanism in your app is up to you. Typically,
you implement consumption for in-app products with temporary benefits
that users may want to purchase multiple times (for example, in-game currency
or equipment). You would typically not want to implement consumption for
or equipment). You typically don't want to implement consumption for
in-app products that are purchased once and provide a permanent effect (for
example, a premium upgrade).
</p>
@@ -576,21 +595,21 @@ if (response == 0) {
To record a purchase consumption, send the {@code consumePurchase} method to
the In-app Billing service and pass in the {@code purchaseToken} String value
that identifies the purchase to be removed. The {@code purchaseToken} is part
of the data returned in the {@code INAPP_PURCHASE_DATA} String by the Google
Play service following a successful purchase request. In this example, you
are recording the consumption of a product that is identified with the {@code
purchaseToken} in the {@code token} variable.
of the data that is returned in the {@code INAPP_PURCHASE_DATA} String by the Google
Play service following a successful purchase request. This example
records the consumption of a product that is identified with the {@code
purchaseToken} in the {@code token} variable:
</p>
<pre>
int response = mService.consumePurchase(3, getPackageName(), token);
</pre>
<p class="note">
<strong>Warning:</strong> Do not call the {@code consumePurchase} method on
the main thread. Calling this method triggers a network request which could
<p class="caution">
<strong>Warning:</strong> Don't call the {@code consumePurchase} method on
the main thread. Calling this method triggers a network request that could
block your main thread. Instead, create a separate thread and call the {@code
consumePurchase} method from inside that thread.
consumePurchase} method from inside of that thread.
</p>
<p>
@@ -600,20 +619,20 @@ int response = mService.consumePurchase(3, getPackageName(), token);
purchased.
</p>
<p class="note">
<strong>Security Recommendation:</strong> You must send a consumption request
<p class="caution">
<strong>Security Recommendation:</strong> Send a consumption request
before provisioning the benefit of the consumable in-app purchase to the
user. Make sure that you have received a successful consumption response from
user. Ensure that you receive a successful consumption response from
Google Play before you provision the item.
</p>
<h3 id="Subs">Implementing Subscriptions</h3>
<h3 id="Subs">Implementing subscriptions</h3>
<p>Launching a purchase flow for a subscription is similar to launching the
purchase flow for a product, with the exception that the product type must be set
to "subs". The purchase result is delivered to your Activity's
{@link android.app.Activity#onActivityResult onActivityResult} method, exactly
as in the case of in-app products.</p>
as in the case of in-app products. Here is an example:</p>
<pre>
Bundle bundle = mService.getBuyIntent(3, "com.example.myapp",
@@ -629,18 +648,18 @@ if (bundle.getInt(RESPONSE_CODE) == BILLING_RESPONSE_RESULT_OK) {
</pre>
<p>To query for active subscriptions, use the {@code getPurchases} method, again
with the product type parameter set to "subs".</p>
with the product type parameter set to "subs":</p>
<pre>
Bundle activeSubs = mService.getPurchases(3, "com.example.myapp",
"subs", continueToken);
</pre>
<p>The call returns a {@code Bundle} with all the active subscriptions owned by
the user. Once a subscription expires without renewal, it will no longer appear
<p>The call returns a {@code Bundle} with all of the active subscriptions that are owned by
the user. When a subscription expires without renewal, it no longer appears
in the returned {@code Bundle}.</p>
<h2 id="billing-security">Securing Your Application</h2>
<h2 id="billing-security">Securing your application</h2>
<p>To help ensure the integrity of the transaction information that is sent to
your application, Google Play signs the JSON string that contains the response
@@ -648,21 +667,21 @@ data for a purchase order. Google Play uses the private key that is associated
with your application in the Developer Console to create this signature. The
Developer Console generates an RSA key pair for each application.<p>
<p class="note"><strong>Note:</strong>To find the public key portion of this key
pair, open your application's details in the Developer Console, then click on
<strong>Services &amp; APIs</strong>, and look at the field titled
<p class="note"><strong>Note:</strong> To find the public key portion of this key
pair, open your application's details in the Developer Console, click
<strong>Services &amp; APIs</strong>, and review the field titled
<strong>Your License Key for This Application</strong>.</p>
<p>The Base64-encoded RSA public key generated by Google Play is in binary
<p>The Base64-encoded RSA public key that is generated by Google Play is in binary
encoded, X.509 subjectPublicKeyInfo DER SEQUENCE format. It is the same public
key that is used with Google Play licensing.</p>
<p>When your application receives this signed response you can
<p>When your application receives this signed response, you can
use the public key portion of your RSA key pair to verify the signature.
By performing signature verification you can detect responses that have
By performing signature verification, you can detect any responses that have
been tampered with or that have been spoofed. You can perform this signature
verification step in your application; however, if your application connects
to a secure remote server then we recommend that you perform the signature
to a secure remote server, Google recommends that you perform the signature
verification on that server.</p>
<p>For more information about best practices for security and design, see <a

276
docs/html/guide/components/bound-services.jd
View File

@@ -8,19 +8,19 @@ parent.link=services.html
<ol id="qv">
<h2>In this document</h2>
<ol>
<li><a href="#Basics">The Basics</a></li>
<li><a href="#Creating">Creating a Bound Service</a>
<li><a href="#Basics">The basics</a></li>
<li><a href="#Creating">Creating a bound service</a>
<ol>
<li><a href="#Binder">Extending the Binder class</a></li>
<li><a href="#Messenger">Using a Messenger</a></li>
</ol>
</li>
<li><a href="#Binding">Binding to a Service</a>
<li><a href="#Binding">Binding to a service</a>
<ol>
<li><a href="#Additional_Notes">Additional notes</a></li>
</ol>
</li>
<li><a href="#Lifecycle">Managing the Lifecycle of a Bound Service</a></li>
<li><a href="#Lifecycle">Managing the lifecycle of a bound service</a></li>
</ol>
<h2>Key classes</h2>
@@ -32,9 +32,13 @@ parent.link=services.html
<h2>Samples</h2>
<ol>
<li><a href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/RemoteService.html">{@code
<li><a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/RemoteService.html">
{@code
RemoteService}</a></li>
<li><a href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/LocalService.html">{@code
<li><a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/LocalService.html">
{@code
LocalService}</a></li>
</ol>
@@ -45,19 +49,23 @@ parent.link=services.html
</div>
<p>A bound service is the server in a client-server interface. A bound service allows components
(such as activities) to bind to the service, send requests, receive responses, and even perform
<p>A bound service is the server in a client-server interface. It allows components
(such as activities) to bind to the service, send requests, receive responses, and perform
interprocess communication (IPC). A bound service typically lives only while it serves another
application component and does not run in the background indefinitely.</p>
<p>This document shows you how to create a bound service, including how to bind
to the service from other application components. However, you should also refer to the <a
href="{@docRoot}guide/components/services.html">Services</a> document for additional
information about services in general, such as how to deliver notifications from a service, set
the service to run in the foreground, and more.</p>
<p class="note"><strong>Note:</strong> If your app targets Android 5.0 (API level 21) or later,
it's recommended that you use the {@link android.app.job.JobScheduler} to execute background
services. For more information about {@link android.app.job.JobScheduler}, see its
{@link android.app.job.JobScheduler API-reference documentation}.</p>
<p>This document describes how to create a bound service, including how to bind
to the service from other application components. For additional information about services in
general, such as how to deliver notifications from a service and set the service to run
in the foreground, refer to the <a href="{@docRoot}guide/components/services.html">
Services</a> document.</p>
<h2 id="Basics">The Basics</h2>
<h2 id="Basics">The basics</h2>
<p>A bound service is an implementation of the {@link android.app.Service} class that allows
other applications to bind to it and interact with it. To provide binding for a
@@ -67,57 +75,61 @@ clients can use to interact with the service.</p>
<div class="sidebox-wrapper">
<div class="sidebox">
<h3>Binding to a Started Service</h3>
<h3>Binding to a started service</h3>
<p>As discussed in the <a href="{@docRoot}guide/components/services.html">Services</a>
document, you can create a service that is both started and bound. That is, the service can be
started by calling {@link android.content.Context#startService startService()}, which allows the
service to run indefinitely, and also allow a client to bind to the service by calling {@link
document, you can create a service that is both started and bound. That is, you can start a
service by calling {@link android.content.Context#startService startService()}, which allows the
service to run indefinitely, and you can also allow a client to bind to the service by
calling {@link
android.content.Context#bindService bindService()}.
<p>If you do allow your service to be started and bound, then when the service has been
started, the system does <em>not</em> destroy the service when all clients unbind. Instead, you must
explicitly stop the service, by calling {@link android.app.Service#stopSelf stopSelf()} or {@link
started, the system does <em>not</em> destroy the service when all clients unbind.
Instead, you must
explicitly stop the service by calling {@link android.app.Service#stopSelf stopSelf()} or {@link
android.content.Context#stopService stopService()}.</p>
<p>Although you should usually implement either {@link android.app.Service#onBind onBind()}
<em>or</em> {@link android.app.Service#onStartCommand onStartCommand()}, it's sometimes necessary to
<p>Although you usually implement either {@link android.app.Service#onBind onBind()}
<em>or</em> {@link android.app.Service#onStartCommand onStartCommand()}, it's sometimes
necessary to
implement both. For example, a music player might find it useful to allow its service to run
indefinitely and also provide binding. This way, an activity can start the service to play some
music and the music continues to play even if the user leaves the application. Then, when the user
returns to the application, the activity can bind to the service to regain control of playback.</p>
returns to the application, the activity can bind to the service to regain control of
playback.</p>
<p>Be sure to read the section about <a href="#Lifecycle">Managing the Lifecycle of a Bound
Service</a>, for more information about the service lifecycle when adding binding to a
started service.</p>
<p>For more information about the service lifecycle when adding binding to a started service,
see <a href="#Lifecycle">Managing the lifecycle of a bound Service</a>.</p>
</div>
</div>
<p>A client can bind to the service by calling {@link android.content.Context#bindService
<p>A client can bind to a service by calling {@link android.content.Context#bindService
bindService()}. When it does, it must provide an implementation of {@link
android.content.ServiceConnection}, which monitors the connection with the service. The {@link
android.content.Context#bindService bindService()} method returns immediately without a value, but
android.content.Context#bindService bindService()} method returns immediately without a
value, but
when the Android system creates the connection between the
client and service, it calls {@link
android.content.ServiceConnection#onServiceConnected onServiceConnected()} on the {@link
android.content.ServiceConnection}, to deliver the {@link android.os.IBinder} that
the client can use to communicate with the service.</p>
<p>Multiple clients can connect to the service at once. However, the system calls your service's
{@link android.app.Service#onBind onBind()} method to retrieve the {@link android.os.IBinder} only
<p>Multiple clients can connect to a service simultaneously. However, the system calls your service's
{@link android.app.Service#onBind onBind()} method to retrieve the
{@link android.os.IBinder} only
when the first client binds. The system then delivers the same {@link android.os.IBinder} to any
additional clients that bind, without calling {@link android.app.Service#onBind onBind()} again.</p>
additional clients that bind, without calling {@link android.app.Service#onBind onBind()}
again.</p>
<p>When the last client unbinds from the service, the system destroys the service (unless the
service was also started by {@link android.content.Context#startService startService()}).</p>
<p>When the last client unbinds from the service, the system destroys the service, unless the
service was also started by {@link android.content.Context#startService startService()}.</p>
<p>When you implement your bound service, the most important part is defining the interface
that your {@link android.app.Service#onBind onBind()} callback method returns. There are a few
different ways you can define your service's {@link android.os.IBinder} interface and the following
section discusses each technique.</p>
<p>The most important part of your bound service implementation is defining the interface
that your {@link android.app.Service#onBind onBind()} callback method returns. The following
section discusses several different ways that you can define your service's
{@link android.os.IBinder} interface.</p>
<h2 id="Creating">Creating a Bound Service</h2>
<h2 id="Creating">Creating a bound service</h2>
<p>When creating a service that provides binding, you must provide an {@link android.os.IBinder}
that provides the programming interface that clients can use to interact with the service. There
@@ -125,12 +137,14 @@ are three ways you can define the interface:</p>
<dl>
<dt><a href="#Binder">Extending the Binder class</a></dt>
<dd>If your service is private to your own application and runs in the same process as the client
(which is common), you should create your interface by extending the {@link android.os.Binder} class
<dd>If your service is private to your own application and runs in the same process
as the client
(which is common), you should create your interface by extending the {@link android.os.Binder}
class
and returning an instance of it from
{@link android.app.Service#onBind onBind()}. The client receives the {@link android.os.Binder} and
can use it to directly access public methods available in either the {@link android.os.Binder}
implementation or even the {@link android.app.Service}.
implementation or the {@link android.app.Service}.
<p>This is the preferred technique when your service is merely a background worker for your own
application. The only reason you would not create your interface this way is because
your service is used by other applications or across separate processes.</dd>
@@ -143,20 +157,20 @@ android.os.Message} objects. This {@link android.os.Handler}
is the basis for a {@link android.os.Messenger} that can then share an {@link android.os.IBinder}
with the client, allowing the client to send commands to the service using {@link
android.os.Message} objects. Additionally, the client can define a {@link android.os.Messenger} of
its own so the service can send messages back.
its own, so the service can send messages back.
<p>This is the simplest way to perform interprocess communication (IPC), because the {@link
android.os.Messenger} queues all requests into a single thread so that you don't have to design
your service to be thread-safe.</p>
</dd>
<dt>Using AIDL</dt>
<dd>AIDL (Android Interface Definition Language) performs all the work to decompose objects into
primitives that the operating system can understand and marshall them across processes to perform
<dt><a href="{@docRoot}guide/components/aidl.html">Using AIDL</a></dt>
<dd>Android Interface Definition Language (AIDL) decomposes objects into
primitives that the operating system can understand and marshals them across processes to perform
IPC. The previous technique, using a {@link android.os.Messenger}, is actually based on AIDL as
its underlying structure. As mentioned above, the {@link android.os.Messenger} creates a queue of
all the client requests in a single thread, so the service receives requests one at a time. If,
however, you want your service to handle multiple requests simultaneously, then you can use AIDL
directly. In this case, your service must be capable of multi-threading and be built thread-safe.
directly. In this case, your service must be thread-safe and capable of multi-threading.
<p>To use AIDL directly, you must
create an {@code .aidl} file that defines the programming interface. The Android SDK tools use
this file to generate an abstract class that implements the interface and handles IPC, which you
@@ -164,19 +178,18 @@ can then extend within your service.</p>
</dd>
</dl>
<p class="note"><strong>Note:</strong> Most applications <strong>should not</strong> use AIDL to
<p class="note"><strong>Note:</strong> Most applications <em>shouldn't</em> use AIDL to
create a bound service, because it may require multithreading capabilities and
can result in a more complicated implementation. As such, AIDL is not suitable for most applications
can result in a more complicated implementation. As such, AIDL is not suitable for
most applications
and this document does not discuss how to use it for your service. If you're certain that you need
to use AIDL directly, see the <a href="{@docRoot}guide/components/aidl.html">AIDL</a>
document.</p>
<h3 id="Binder">Extending the Binder class</h3>
<p>If your service is used only by the local application and does not need to work across processes,
<p>If your service is used only by the local application and does not need to
work across processes,
then you can implement your own {@link android.os.Binder} class that provides your client direct
access to public methods in the service.</p>
@@ -187,13 +200,14 @@ background.</p>
<p>Here's how to set it up:</p>
<ol>
<li>In your service, create an instance of {@link android.os.Binder} that either:
<li>In your service, create an instance of {@link android.os.Binder} that does
one of the following:
<ul>
<li>contains public methods that the client can call</li>
<li>returns the current {@link android.app.Service} instance, which has public methods the
client can call</li>
<li>or, returns an instance of another class hosted by the service with public methods the
client can call</li>
<li>Contains public methods that the client can call.</li>
<li>Returns the current {@link android.app.Service} instance, which has public methods the
client can call.</li>
<li>Returns an instance of another class hosted by the service with public methods the
client can call.</li>
</ul>
<li>Return this instance of {@link android.os.Binder} from the {@link
android.app.Service#onBind onBind()} callback method.</li>
@@ -202,12 +216,13 @@ android.content.ServiceConnection#onServiceConnected onServiceConnected()} callb
make calls to the bound service using the methods provided.</li>
</ol>
<p class="note"><strong>Note:</strong> The reason the service and client must be in the same
application is so the client can cast the returned object and properly call its APIs. The service
<p class="note"><strong>Note:</strong> The service and client must be in the same
application so that the client can cast the returned object and properly call its APIs.
The service
and client must also be in the same process, because this technique does not perform any
marshalling across processes.</p>
marshaling across processes.</p>
<p>For example, here's a service that provides clients access to methods in the service through
<p>For example, here's a service that provides clients with access to methods in the service through
a {@link android.os.Binder} implementation:</p>
<pre>
@@ -316,32 +331,30 @@ section provides more information about this process of binding to the service.<
<p class="note"><strong>Note:</strong> In the example above, the
{@link android.app.Activity#onStop onStop()} method unbinds the client from the service. Clients
should unbind from services at appropriate times, as discussed in
<a href="#Additional_Notes">Additional Notes</a>.
<a href="#Additional_Notes">Additional notes</a>.
</p>
<p>For more sample code, see the <a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/LocalService.html">{@code
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/LocalService.html">
{@code
LocalService.java}</a> class and the <a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/LocalServiceActivities.html">{@code
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/LocalServiceActivities.html">
{@code
LocalServiceActivities.java}</a> class in <a
href="{@docRoot}resources/samples/ApiDemos/index.html">ApiDemos</a>.</p>
<h3 id="Messenger">Using a Messenger</h3>
<div class="sidebox-wrapper">
<div class="sidebox">
<h4>Compared to AIDL</h4>
<p>When you need to perform IPC, using a {@link android.os.Messenger} for your interface is
simpler than implementing it with AIDL, because {@link android.os.Messenger} queues
all calls to the service, whereas, a pure AIDL interface sends simultaneous requests to the
simpler than using AIDL, because {@link android.os.Messenger} queues
all calls to the service. A pure AIDL interface sends simultaneous requests to the
service, which must then handle multi-threading.</p>
<p>For most applications, the service doesn't need to perform multi-threading, so using a {@link
android.os.Messenger} allows the service to handle one call at a time. If it's important
that your service be multi-threaded, then you should use <a
that your service be multi-threaded, use <a
href="{@docRoot}guide/components/aidl.html">AIDL</a> to define your interface.</p>
</div>
</div>
@@ -352,10 +365,11 @@ you to perform interprocess communication (IPC) without the need to use AIDL.</p
<p>Here's a summary of how to use a {@link android.os.Messenger}:</p>
<ul>
<ol>
<li>The service implements a {@link android.os.Handler} that receives a callback for each
call from a client.</li>
<li>The {@link android.os.Handler} is used to create a {@link android.os.Messenger} object
<li>The service uses the {@link android.os.Handler} to create a {@link android.os.Messenger}
object
(which is a reference to the {@link android.os.Handler}).</li>
<li>The {@link android.os.Messenger} creates an {@link android.os.IBinder} that the service
returns to clients from {@link android.app.Service#onBind onBind()}.</li>
@@ -365,11 +379,12 @@ returns to clients from {@link android.app.Service#onBind onBind()}.</li>
<li>The service receives each {@link android.os.Message} in its {@link
android.os.Handler}&mdash;specifically, in the {@link android.os.Handler#handleMessage
handleMessage()} method.</li>
</ul>
</ol>
<p>In this way, there are no "methods" for the client to call on the service. Instead, the
client delivers "messages" ({@link android.os.Message} objects) that the service receives in
<p>In this way, there are no <em>methods</em> for the client to call on the service. Instead, the
client delivers <em>messages</em> ({@link android.os.Message} objects) that the service
receives in
its {@link android.os.Handler}.</p>
<p>Here's a simple example service that uses a {@link android.os.Messenger} interface:</p>
@@ -488,41 +503,42 @@ public class ActivityMessenger extends Activity {
}
</pre>
<p>Notice that this example does not show how the service can respond to the client. If you want the
service to respond, then you need to also create a {@link android.os.Messenger} in the client. Then
when the client receives the {@link android.content.ServiceConnection#onServiceConnected
<p>Notice that this example does not show how the service can respond to the client.
If you want the
service to respond, you need to also create a {@link android.os.Messenger} in the client.
When the client receives the {@link android.content.ServiceConnection#onServiceConnected
onServiceConnected()} callback, it sends a {@link android.os.Message} to the service that includes
the client's {@link android.os.Messenger} in the {@link android.os.Message#replyTo} parameter
of the {@link android.os.Messenger#send send()} method.</p>
<p>You can see an example of how to provide two-way messaging in the <a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/MessengerService.html">{@code
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/MessengerService.html">
{@code
MessengerService.java}</a> (service) and <a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/MessengerServiceActivities.html">{@code
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/MessengerServiceActivities.html">
{@code
MessengerServiceActivities.java}</a> (client) samples.</p>
<h2 id="Binding">Binding to a Service</h2>
<h2 id="Binding">Binding to a service</h2>
<p>Application components (clients) can bind to a service by calling
{@link android.content.Context#bindService bindService()}. The Android
system then calls the service's {@link android.app.Service#onBind
onBind()} method, which returns an {@link android.os.IBinder} for interacting with the service.</p>
onBind()} method, which returns an {@link android.os.IBinder} for interacting with
the service.</p>
<p>The binding is asynchronous. {@link android.content.Context#bindService
bindService()} returns immediately and does <em>not</em> return the {@link android.os.IBinder} to
the client. To receive the {@link android.os.IBinder}, the client must create an instance of {@link
<p>The binding is asynchronous, and {@link android.content.Context#bindService
bindService()} returns immediately without <em>not</em> returning the {@link android.os.IBinder} to
the client. To receive the {@link android.os.IBinder}, the client must create an
instance of {@link
android.content.ServiceConnection} and pass it to {@link android.content.Context#bindService
bindService()}. The {@link android.content.ServiceConnection} includes a callback method that the
system calls to deliver the {@link android.os.IBinder}.</p>
<p class="note"><strong>Note:</strong> Only activities, services, and content providers can bind
to a service&mdash;you <strong>cannot</strong> bind to a service from a broadcast receiver.</p>
to a service&mdash;you <strong>can't</strong> bind to a service from a broadcast receiver.</p>
<p>So, to bind to a service from your client, you must: </p>
<p>To bind to a service from your client, follow these steps: </p>
<ol>
<li>Implement {@link android.content.ServiceConnection}.
<p>Your implementation must override two callback methods:</p>
@@ -533,7 +549,8 @@ the service's {@link android.app.Service#onBind onBind()} method.</dd>
<dt>{@link android.content.ServiceConnection#onServiceDisconnected
onServiceDisconnected()}</dt>
<dd>The Android system calls this when the connection to the service is unexpectedly
lost, such as when the service has crashed or has been killed. This is <em>not</em> called when the
lost, such as when the service has crashed or has been killed. This is <em>not</em>
called when the
client unbinds.</dd>
</dl>
</li>
@@ -548,12 +565,12 @@ android.content.Context#unbindService unbindService()}.
<p>If your client is still bound to a service when your app destroys the client, destruction
causes the client to unbind. It is better practice to unbind the client as soon as it is done
interacting with the service. Doing so allows the idle service to shut down. For more information
about appropriate times to bind and unbind, see <a href="#Additional_Notes">Additional Notes</a>.
about appropriate times to bind and unbind, see <a href="#Additional_Notes">Additional notes</a>.
</p>
</li>
</ol>
<p>For example, the following snippet connects the client to the service created above by
<p>The following example connects the client to the service created above by
<a href="#Binder">extending the Binder class</a>, so all it must do is cast the returned
{@link android.os.IBinder} to the {@code LocalService} class and request the {@code
LocalService} instance:</p>
@@ -579,8 +596,9 @@ private ServiceConnection mConnection = new ServiceConnection() {
};
</pre>
<p>With this {@link android.content.ServiceConnection}, the client can bind to a service by passing
it to {@link android.content.Context#bindService bindService()}. For example:</p>
<p>With this {@link android.content.ServiceConnection}, the client can bind to a service
by passing
it to {@link android.content.Context#bindService bindService()}, as shown in the following example:</p>
<pre>
Intent intent = new Intent(this, LocalService.class);
@@ -589,11 +607,21 @@ bindService(intent, mConnection, Context.BIND_AUTO_CREATE);
<ul>
<li>The first parameter of {@link android.content.Context#bindService bindService()} is an
{@link android.content.Intent} that explicitly names the service to bind (thought the intent
could be implicit).</li>
{@link android.content.Intent} that explicitly names the service to bind.
<p class="caution"><strong>Caution:</strong> If you use an intent to bind to a
{@link android.app.Service}, ensure that your app is secure by using an <a href="{@docRoot}guide/components/intents-filters.html#Types">explicit</a>
intent. Using an implicit intent to start a service is a
security hazard because you can't be certain what service will respond to the intent,
and the user can't see which service starts. Beginning with Android 5.0 (API level 21),
the system
throws an exception if you call {@link android.content.Context#bindService bindService()}
with an implicit intent.</p>
</li>
<li>The second parameter is the {@link android.content.ServiceConnection} object.</li>
<li>The third parameter is a flag indicating options for the binding. It should usually be {@link
android.content.Context#BIND_AUTO_CREATE} in order to create the service if its not already alive.
android.content.Context#BIND_AUTO_CREATE} in order to create the service if it's not already
alive.
Other possible values are {@link android.content.Context#BIND_DEBUG_UNBIND}
and {@link android.content.Context#BIND_NOT_FOREGROUND}, or {@code 0} for none.</li>
</ul>
@@ -606,10 +634,11 @@ and {@link android.content.Context#BIND_NOT_FOREGROUND}, or {@code 0} for none.<
<li>You should always trap {@link android.os.DeadObjectException} exceptions, which are thrown
when the connection has broken. This is the only exception thrown by remote methods.</li>
<li>Objects are reference counted across processes. </li>
<li>You should usually pair the binding and unbinding during
matching bring-up and tear-down moments of the client's lifecycle. For example:
<li>You usually pair the binding and unbinding during
matching bring-up and tear-down moments of the client's lifecycle, as described in the
following examples:
<ul>
<li>If you only need to interact with the service while your activity is visible, you
<li>If you need to interact with the service only while your activity is visible, you
should bind during {@link android.app.Activity#onStart onStart()} and unbind during {@link
android.app.Activity#onStop onStop()}.</li>
<li>If you want your activity to receive responses even while it is stopped in the
@@ -619,33 +648,34 @@ activity needs to use the service the entire time it's running (even in the back
the service is in another process, then you increase the weight of the process and it becomes
more likely that the system will kill it.</li>
</ul>
<p class="note"><strong>Note:</strong> You should usually <strong>not</strong> bind and unbind
<p class="note"><strong>Note:</strong> You <em>don't</em> usually bind and unbind
during your activity's {@link android.app.Activity#onResume onResume()} and {@link
android.app.Activity#onPause onPause()}, because these callbacks occur at every lifecycle transition
android.app.Activity#onPause onPause()}, because these callbacks occur at every
lifecycle transition
and you should keep the processing that occurs at these transitions to a minimum. Also, if
multiple activities in your application bind to the same service and there is a transition between
two of those activities, the service may be destroyed and recreated as the current activity unbinds
(during pause) before the next one binds (during resume). (This activity transition for how
multiple activities in your application bind to the same service and there is a
transition between
two of those activities, the service may be destroyed and recreated as the current
activity unbinds
(during pause) before the next one binds (during resume). This activity transition for how
activities coordinate their lifecycles is described in the <a
href="{@docRoot}guide/components/activities.html#CoordinatingActivities">Activities</a>
document.)</p>
document.</p>
</ul>
<p>For more sample code, showing how to bind to a service, see the <a
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/RemoteService.html">{@code
href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/app/RemoteService.html">
{@code
RemoteService.java}</a> class in <a
href="{@docRoot}resources/samples/ApiDemos/index.html">ApiDemos</a>.</p>
<h2 id="Lifecycle">Managing the Lifecycle of a Bound Service</h2>
<h2 id="Lifecycle">Managing the lifecycle of a bound service</h2>
<p>When a service is unbound from all clients, the Android system destroys it (unless it was also
started with {@link android.app.Service#onStartCommand onStartCommand()}). As such, you don't have
to manage the lifecycle of your service if it's purely a bound
service&mdash;the Android system manages it for you based on whether it is bound to any clients.</p>
service&mdash;the Android system manages it for you based on whether it is bound to
any clients.</p>
<p>However, if you choose to implement the {@link android.app.Service#onStartCommand
onStartCommand()} callback method, then you must explicitly stop the service, because the
@@ -660,17 +690,11 @@ your {@link android.app.Service#onUnbind onUnbind()} method, you can optionally
onRebind()} the next time a client binds to the service. {@link android.app.Service#onRebind
onRebind()} returns void, but the client still receives the {@link android.os.IBinder} in its
{@link android.content.ServiceConnection#onServiceConnected onServiceConnected()} callback.
Below, figure 1 illustrates the logic for this kind of lifecycle.</p>
The following figure illustrates the logic for this kind of lifecycle.</p>
<img src="{@docRoot}images/fundamentals/service_binding_tree_lifecycle.png" alt="" />
<p class="img-caption"><strong>Figure 1.</strong> The lifecycle for a service that is started
and also allows binding.</p>
<p>For more information about the lifecycle of a started service, see the <a
href="{@docRoot}guide/components/services.html#Lifecycle">Services</a> document.</p>

316
docs/html/guide/components/fundamentals.jd
View File

@@ -6,28 +6,29 @@ page.title=Application Fundamentals
<h2>In this document</h2>
<ol>
<li><a href="#Components">App Components</a>
<li><a href="#Components">App components</a>
<ol>
<li><a href="#ActivatingComponents">Activating components</a></li>
</ol>
</li>
<li><a href="#Manifest">The Manifest File</a>
<li><a href="#Manifest">The manifest file</a>
<ol>
<li><a href="#DeclaringComponents">Declaring components</a></li>
<li><a href="#DeclaringRequirements">Declaring app requirements</a></li>
</ol>
</li>
<li><a href="#Resources">App Resources</a></li>
<li><a href="#Resources">App resources</a></li>
</ol>
</div>
</div>
<p>Android apps are written in the Java programming language. The Android SDK tools compile
your code&mdash;along with any data and resource files&mdash;into an APK: an <i>Android package</i>,
your code along with any data and resource files into an APK, an <i>Android package</i>,
which is an archive file with an {@code .apk} suffix. One APK file contains all the contents
of an Android app and is the file that Android-powered devices use to install the app.</p>
<p>Once installed on a device, each Android app lives in its own security sandbox: </p>
<p>Each Android app lives in its own security sandbox, protected by
the following Android security features: </p>
<ul>
<li>The Android operating system is a multi-user Linux system in which each app is a
@@ -40,54 +41,61 @@ app so that only the user ID assigned to that app can access them. </li>
<li>Each process has its own virtual machine (VM), so an app's code runs in isolation from
other apps.</li>
<li>By default, every app runs in its own Linux process. Android starts the process when any
of the app's components need to be executed, then shuts down the process when it's no longer
<li>By default, every app runs in its own Linux process. The Android system starts
the process when any
of the app's components need to be executed, and then shuts down the process
when it's no longer
needed or when the system must recover memory for other apps.</li>
</ul>
<p>In this way, the Android system implements the <em>principle of least privilege</em>. That is,
<p>The Android system implements the <em>principle of least privilege</em>. That is,
each app, by default, has access only to the components that it requires to do its work and
no more. This creates a very secure environment in which an app cannot access parts of
the system for which it is not given permission.</p>
<p>However, there are ways for an app to share data with other apps and for an
the system for which it is not given permission. However, there are ways for an app to share
data with other apps and for an
app to access system services:</p>
<ul>
<li>It's possible to arrange for two apps to share the same Linux user ID, in which case
they are able to access each other's files. To conserve system resources, apps with the
same user ID can also arrange to run in the same Linux process and share the same VM (the
apps must also be signed with the same certificate).</li>
same user ID can also arrange to run in the same Linux process and share the same VM. The
apps must also be signed with the same certificate.</li>
<li>An app can request permission to access device data such as the user's
contacts, SMS messages, the mountable storage (SD card), camera, Bluetooth, and more. The user has
contacts, SMS messages, the mountable storage (SD card), camera, and Bluetooth. The user has
to explicitly grant these permissions. For more information, see
<a href="{@docRoot}training/permissions/index.html">Working with System Permissions</a>.</li>
</ul>
<p>That covers the basics regarding how an Android app exists within the system. The rest of
this document introduces you to:</p>
<p>The rest of this document introduces the following concepts:</p>
<ul>
<li>The core framework components that define your app.</li>
<li>The manifest file in which you declare components and required device features for your
<li>The manifest file in which you declare the components and the required device
features for your
app.</li>
<li>Resources that are separate from the app code and allow your app to
<li>Resources that are separate from the app code and that allow your app to
gracefully optimize its behavior for a variety of device configurations.</li>
</ul>
<h2 id="Components">App Components</h2>
<h2 id="Components">App components</h2>
<p>App components are the essential building blocks of an Android app. Each
component is a different point through which the system can enter your app. Not all
components are actual entry points for the user and some depend on each other, but each one exists
as its own entity and plays a specific role&mdash;each one is a unique building block that
helps define your app's overall behavior.</p>
components are actual entry points for the user and some depend on each other,
but each one exists
as its own entity and plays a specific role.</p>
<p>There are four different types of app components. Each type serves a distinct purpose
and has a distinct lifecycle that defines how the component is created and destroyed.</p>
<p>Here are the four types of app components:</p>
<p>There are four different types of app components:
<ul>
<li>Activities.</li>
<li>Services.</li>
<li>Content providers.</li>
<li>Broadcast receivers.</li>
</ul></p>
Each type serves a distinct purpose
and has a distinct lifecycle that defines how the component is created and destroyed.
The following sections describe the four types of app components.</p>
<dl>
@@ -98,11 +106,12 @@ an email app might have one activity that shows a list of new
emails, another activity to compose an email, and another activity for reading emails. Although
the activities work together to form a cohesive user experience in the email app, each one
is independent of the others. As such, a different app can start any one of these
activities (if the email app allows it). For example, a camera app can start the
activity in the email app that composes new mail, in order for the user to share a picture.
activities if the email app allows it. For example, a camera app can start the
activity in the email app that composes new mail to allow the user to share a picture.
<p>An activity is implemented as a subclass of {@link android.app.Activity} and you can learn more
about it in the <a href="{@docRoot}guide/components/activities.html">Activities</a>
<p>An activity is implemented as a subclass of {@link android.app.Activity}. You can learn more
about {@link android.app.Activity} in the
<a href="{@docRoot}guide/components/activities.html">Activities</a>
developer guide.</p>
</dd>
@@ -111,13 +120,16 @@ developer guide.</p>
<dd>A <i>service</i> is a component that runs in the background to perform long-running
operations or to perform work for remote processes. A service
does not provide a user interface. For example, a service might play music in the background while
does not provide a user interface. For example, a service might play music in the
background while
the user is in a different app, or it might fetch data over the network without
blocking user interaction with an activity. Another component, such as an activity, can start the
blocking user interaction with an activity. Another component, such as an activity,
can start the
service and let it run or bind to it in order to interact with it.
<p>A service is implemented as a subclass of {@link android.app.Service} and you can learn more
about it in the <a href="{@docRoot}guide/components/services.html">Services</a> developer
<p>A service is implemented as a subclass of {@link android.app.Service}. You can learn more
about {@link android.app.Service} in the <a href="{@docRoot}guide/components/services.html">
Services</a> developer
guide.</p>
</dd>
@@ -125,12 +137,14 @@ guide.</p>
<dt><b>Content providers</b></dt>
<dd>A <i>content provider</i> manages a shared set of app data. You can store the data in
the file system, an SQLite database, on the web, or any other persistent storage location your
app can access. Through the content provider, other apps can query or even modify
the data (if the content provider allows it). For example, the Android system provides a content
the file system, in a SQLite database, on the web, or on any other persistent storage
location that your
app can access. Through the content provider, other apps can query or modify
the data if the content provider allows it. For example, the Android system provides a content
provider that manages the user's contact information. As such, any app with the proper
permissions can query part of the content provider (such as {@link
android.provider.ContactsContract.Data}) to read and write information about a particular person.
permissions can query part of the content provider, such as {@link
android.provider.ContactsContract.Data}, to read and write information about
a particular person.
<p>Content providers are also useful for reading and writing data that is private to your
app and not shared. For example, the <a
@@ -148,15 +162,17 @@ guide.</p>
<dt><b>Broadcast receivers</b></dt>
<dd>A <i>broadcast receiver</i> is a component that responds to system-wide broadcast
announcements. Many broadcasts originate from the system&mdash;for example, a broadcast announcing
announcements. Many broadcasts originate from the system&mdash;for example,
a broadcast announcing
that the screen has turned off, the battery is low, or a picture was captured.
Apps can also initiate broadcasts&mdash;for example, to let other apps know that
some data has been downloaded to the device and is available for them to use. Although broadcast
some data has been downloaded to the device and is available for them to use.
Although broadcast
receivers don't display a user interface, they may <a
href="{@docRoot}guide/topics/ui/notifiers/notifications.html">create a status bar notification</a>
to alert the user when a broadcast event occurs. More commonly, though, a broadcast receiver is
just a "gateway" to other components and is intended to do a very minimal amount of work. For
instance, it might initiate a service to perform some work based on the event.
just a <em>gateway</em> to other components and is intended to do a very minimal amount of work.
For instance, it might initiate a service to perform some work based on the event.
<p>A broadcast receiver is implemented as a subclass of {@link android.content.BroadcastReceiver}
and each broadcast is delivered as an {@link android.content.Intent} object. For more information,
@@ -170,52 +186,59 @@ see the {@link android.content.BroadcastReceiver} class.</p>
<p>A unique aspect of the Android system design is that any app can start another
app’s component. For example, if you want the user to capture a
photo with the device camera, there's probably another app that does that and your
app can use it, instead of developing an activity to capture a photo yourself. You don't
app can use it instead of developing an activity to capture a photo yourself. You don't
need to incorporate or even link to the code from the camera app.
Instead, you can simply start the activity in the camera app that captures a
photo. When complete, the photo is even returned to your app so you can use it. To the user,
it seems as if the camera is actually a part of your app.</p>
<p>When the system starts a component, it starts the process for that app (if it's not
already running) and instantiates the classes needed for the component. For example, if your
<p>When the system starts a component, it starts the process for that app if it's not
already running and instantiates the classes needed for the component. For example, if your
app starts the activity in the camera app that captures a photo, that activity
runs in the process that belongs to the camera app, not in your app's process.
Therefore, unlike apps on most other systems, Android apps don't have a single entry
point (there's no {@code main()} function, for example).</p>
point (there's no {@code main()} function).</p>
<p>Because the system runs each app in a separate process with file permissions that
restrict access to other apps, your app cannot directly activate a component from
another app. The Android system, however, can. So, to activate a component in
another app, you must deliver a message to the system that specifies your <em>intent</em> to
another app. However, the Android system can. To activate a component in
another app, deliver a message to the system that specifies your <em>intent</em> to
start a particular component. The system then activates the component for you.</p>
<h3 id="ActivatingComponents">Activating Components</h3>
<h3 id="ActivatingComponents">Activating components</h3>
<p>Three of the four component types&mdash;activities, services, and
broadcast receivers&mdash;are activated by an asynchronous message called an <em>intent</em>.
Intents bind individual components to each other at runtime (you can think of them
as the messengers that request an action from other components), whether the component belongs
Intents bind individual components to each other at runtime. You can think of them
as the messengers that request an action from other components, whether the component belongs
to your app or another.</p>
<p>An intent is created with an {@link android.content.Intent} object, which defines a message to
activate either a specific component or a specific <em>type</em> of component&mdash;an intent
can be either explicit or implicit, respectively.</p>
<p class="note"><strong>Note:</strong> If your app targets Android 5.0 (API level 21) or later,
use the {@link android.app.job.JobScheduler} to execute background
services. For more information about using this class, see the
{@link android.app.job.JobScheduler} reference documentation.</p>
<p>For activities and services, an intent defines the action to perform (for example, to "view" or
"send" something) and may specify the URI of the data to act on (among other things that the
component being started might need to know). For example, an intent might convey a request for an
<p>An intent is created with an {@link android.content.Intent} object, which defines a message to
activate either a specific component (explicit intent) or a specific <em>type</em> of component
(implicit intent).</p>
<p>For activities and services, an intent defines the action to perform (for example, to
<em>view</em> or
<em>send</em> something) and may specify the URI of the data to act on, among other things that the
component being started might need to know. For example, an intent might convey a request for an
activity to show an image or to open a web page. In some cases, you can start an
activity to receive a result, in which case, the activity also returns
the result in an {@link android.content.Intent} (for example, you can issue an intent to let
the user pick a personal contact and have it returned to you&mdash;the return intent includes a
URI pointing to the chosen contact).</p>
activity to receive a result, in which case the activity also returns
the result in an {@link android.content.Intent}. For example, you can issue an intent to let
the user pick a personal contact and have it returned to you. The return intent includes a
URI pointing to the chosen contact.</p>
<p>For broadcast receivers, the intent simply defines the
announcement being broadcast (for example, a broadcast to indicate the device battery is low
includes only a known action string that indicates "battery is low").</p>
announcement being broadcast. For example, a broadcast to indicate the device battery is low
includes only a known action string that indicates <em>battery is low</em>.</p>
<p>The other component type, content provider, is not activated by intents. Rather, it is
<p>Unlike activities, services, and broadcast receivers, content providers are not activated
by intents. Rather, they are
activated when targeted by a request from a {@link android.content.ContentResolver}. The content
resolver handles all direct transactions with the content provider so that the component that's
performing transactions with the provider doesn't need to and instead calls methods on the {@link
@@ -224,15 +247,19 @@ provider and the component requesting information (for security).</p>
<p>There are separate methods for activating each type of component:</p>
<ul>
<li>You can start an activity (or give it something new to do) by
<li>You can start an activity or give it something new to do by
passing an {@link android.content.Intent} to {@link android.content.Context#startActivity
startActivity()} or {@link android.app.Activity#startActivityForResult startActivityForResult()}
(when you want the activity to return a result).</li>
<li>You can start a service (or give new instructions to an ongoing service) by
<li>With Android 5.0 (API level 21) and later, you can start a service with
{@link android.app.job.JobScheduler}. For earlier Android versions, you can start
a service (or give new instructions to an ongoing service) by
passing an {@link android.content.Intent} to {@link android.content.Context#startService
startService()}. Or you can bind to the service by passing an {@link android.content.Intent} to
{@link android.content.Context#bindService bindService()}.</li>
<li>You can initiate a broadcast by passing an {@link android.content.Intent} to methods like
startService()}. You can bind to the service by passing an {@link android.content.Intent} to
{@link android.content.Context#bindService bindService()}. </li>
<li>You can initiate a broadcast by passing an {@link android.content.Intent} to methods such as
{@link android.content.Context#sendBroadcast(Intent) sendBroadcast()}, {@link
android.content.Context#sendOrderedBroadcast(Intent, String) sendOrderedBroadcast()}, or {@link
android.content.Context#sendStickyBroadcast sendStickyBroadcast()}.</li>
@@ -242,35 +269,35 @@ android.content.ContentProvider#query query()} on a {@link android.content.Conte
<p>For more information about using intents, see the <a
href="{@docRoot}guide/components/intents-filters.html">Intents and
Intent Filters</a> document. More information about activating specific components is also provided
in the following documents: <a
href="{@docRoot}guide/components/activities.html">Activities</a>, <a
href="{@docRoot}guide/components/services.html">Services</a>, {@link
android.content.BroadcastReceiver} and <a
href="{@docRoot}guide/topics/providers/content-providers.html">Content Providers</a>.</p>
Intent Filters</a> document.
The following documents provide more information about activating specifc components:
<a href="{@docRoot}guide/components/activities.html">Activities</a>,
<a href="{@docRoot}guide/components/services.html">Services
{@link android.content.BroadcastReceiver}, and
<a ref="{@docRoot}guide/topics/providers/content-providers.html">Content Providers</a>.</p>
<h2 id="Manifest">The Manifest File</h2>
<h2 id="Manifest">The manifest file</h2>
<p>Before the Android system can start an app component, the system must know that the
component exists by reading the app's {@code AndroidManifest.xml} file (the "manifest"
file). Your app must declare all its components in this file, which must be at the root of
the app project directory.</p>
component exists by reading the app's <em>manifest file</em>, {@code AndroidManifest.xml}.
Your app must declare all its components in this file, which must be at the root of the
app project directory.</p>
<p>The manifest does a number of things in addition to declaring the app's components,
such as:</p>
such as the following:</p>
<ul>
<li>Identify any user permissions the app requires, such as Internet access or
<li>Identifies any user permissions the app requires, such as Internet access or
read-access to the user's contacts.</li>
<li>Declare the minimum <a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#ApiLevels">API Level</a>
<li>Declares the minimum
<a href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#ApiLevels">API Level</a>
required by the app, based on which APIs the app uses.</li>
<li>Declare hardware and software features used or required by the app, such as a camera,
<li>Declares hardware and software features used or required by the app, such as a camera,
bluetooth services, or a multitouch screen.</li>
<li>API libraries the app needs to be linked against (other than the Android framework
<li>Declares API libraries the app needs to be linked against (other than the Android framework
APIs), such as the <a
href="http://code.google.com/android/add-ons/google-apis/maps-overview.html">Google Maps
library</a>.</li>
<li>And more</li>
href="http://code.google.com/android/add-ons/google-apis/maps-overview.html">
Google Maps library</a>.</li>
</ul>
@@ -301,47 +328,59 @@ the {@code android:name} attribute specifies the fully qualified class name of t
android.app.Activity} subclass and the {@code android:label} attribute specifies a string
to use as the user-visible label for the activity.</p>
<p>You must declare all app components this way:</p>
<p>You must declare all app components using the following elements:</p>
<ul>
<li><code><a
href="{@docRoot}guide/topics/manifest/activity-element.html">&lt;activity&gt;</a></code> elements
for activities</li>
for activities.</li>
<li><code><a
href="{@docRoot}guide/topics/manifest/service-element.html">&lt;service&gt;</a></code> elements for
services</li>
services.</li>
<li><code><a
href="{@docRoot}guide/topics/manifest/receiver-element.html">&lt;receiver&gt;</a></code> elements
for broadcast receivers</li>
for broadcast receivers.</li>
<li><code><a
href="{@docRoot}guide/topics/manifest/provider-element.html">&lt;provider&gt;</a></code> elements
for content providers</li>
for content providers.</li>
</ul>
<p>Activities, services, and content providers that you include in your source but do not declare
in the manifest are not visible to the system and, consequently, can never run. However,
broadcast
receivers can be either declared in the manifest or created dynamically in code (as
{@link android.content.BroadcastReceiver} objects) and registered with the system by calling
receivers can be either declared in the manifest or created dynamically in code as
{@link android.content.BroadcastReceiver} objects and registered with the system by calling
{@link android.content.Context#registerReceiver registerReceiver()}.</p>
<p>For more about how to structure the manifest file for your app, see <a
href="{@docRoot}guide/topics/manifest/manifest-intro.html">The AndroidManifest.xml File</a>
documentation. </p>
<h3 id="DeclaringComponentCapabilities">Declaring component capabilities</h3>
<p>As discussed above, in <a href="#ActivatingComponents">Activating Components</a>, you can use an
{@link android.content.Intent} to start activities, services, and broadcast receivers. You can do so
by explicitly naming the target component (using the component class name) in the intent. However,
the real power of intents lies in the concept of <em>implicit intents</em>. An implicit intent
simply describes the type of action to perform (and, optionally, the data upon which you’d like to
perform the action) and allows the system to find a component on the device that can perform the
action and start it. If there are multiple components that can perform the action described by the
intent, then the user selects which one to use.</p>
<p>As discussed above, in <a href="#ActivatingComponents">Activating components</a>, you can use an
{@link android.content.Intent} to start activities, services, and broadcast receivers.
<p>The way the system identifies the components that can respond to an intent is by comparing the
You can use an {@link android.content.Intent}
by explicitly naming the target component (using the component class name) in the intent.
You can also use an implicit intent, which
describes the type of action to perform and, optionally, the data upon which you’d like to
perform the action. The implicit intent allows the system to find a component on the device
that can perform the
action and start it. If there are multiple components that can perform the action described by the
intent, the user selects which one to use.</p>
<p class="caution"><strong>Caution:</strong> If you use an intent to start a
{@link android.app.Service}, ensure that your app is secure by using an
<a href="{@docRoot}guide/components/intents-filters.html#Types">explicit</a>
intent. Using an implicit intent to start a service is a
security hazard because you cannot be certain what service will respond to the intent,
and the user cannot see which service starts. Beginning with Android 5.0 (API level 21), the system
throws an exception if you call {@link android.content.Context#bindService bindService()}
with an implicit intent. Do not declare intent filters for your services. </p>
<p>The system identifies the components that can respond to an intent by comparing the
intent received to the <i>intent filters</i> provided in the manifest file of other apps on
the device.</p>
@@ -351,8 +390,9 @@ from other apps. You can declare an intent filter for your component by
adding an <a href="{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code
<intent-filter>}</a> element as a child of the component's declaration element.</p>
<p>For example, if you've built an email app with an activity for composing a new email, you can
declare an intent filter to respond to "send" intents (in order to send a new email) like this:</p>
<p>For example, if you build an email app with an activity for composing a new email, you can
declare an intent filter to respond to "send" intents (in order to send a new email),
as shown in the following example:</p>
<pre>
&lt;manifest ... >
...
@@ -368,8 +408,9 @@ declare an intent filter to respond to "send" intents (in order to send a new em
&lt;/manifest>
</pre>
<p>Then, if another app creates an intent with the {@link
android.content.Intent#ACTION_SEND} action and passes it to {@link android.app.Activity#startActivity
<p>If another app creates an intent with the {@link
android.content.Intent#ACTION_SEND} action and passes it to
{@link android.app.Activity#startActivity
startActivity()}, the system may start your activity so the user can draft and send an
email.</p>
@@ -382,7 +423,7 @@ href="{@docRoot}guide/components/intents-filters.html">Intents and Intent Filter
<h3 id="DeclaringRequirements">Declaring app requirements</h3>
<p>There are a variety of devices powered by Android and not all of them provide the
same features and capabilities. In order to prevent your app from being installed on devices
same features and capabilities. To prevent your app from being installed on devices
that lack features needed by your app, it's important that you clearly define a profile for
the types of devices your app supports by declaring device and software requirements in your
manifest file. Most of these declarations are informational only and the system does not read
@@ -391,7 +432,7 @@ for users when they search for apps from their device.</p>
<p>For example, if your app requires a camera and uses APIs introduced in Android 2.1 (<a
href="{@docRoot}guide/topics/manifest/uses-sdk-element.html#ApiLevels">API Level</a> 7),
you should declare these as requirements in your manifest file like this:</p>
you must declare these as requirements in your manifest file as shown in the following example:</p>
<pre>
&lt;manifest ... >
@@ -402,10 +443,10 @@ you should declare these as requirements in your manifest file like this:</p>
&lt;/manifest>
</pre>
<p>Now, devices that do <em>not</em> have a camera and have an
Android version <em>lower</em> than 2.1 cannot install your app from Google Play.</p>
<p>However, you can also declare that your app uses the camera, but does not
<p>With the declarations shown in the example, devices that do <em>not</em> have a
camera and have an
Android version <em>lower</em> than 2.1 cannot install your app from Google Play.
However, you can declare that your app uses the camera, but does not
<em>require</em> it. In that case, your app must set the <a href=
"{@docRoot}guide/topics/manifest/uses-feature-element.html#required">{@code required}</a>
attribute to {@code "false"} and check at runtime whether
@@ -417,15 +458,15 @@ document.</p>
<h2 id="Resources">App Resources</h2>
<h2 id="Resources">App resources</h2>
<p>An Android app is composed of more than just code&mdash;it requires resources that are
separate from the source code, such as images, audio files, and anything relating to the visual
presentation of the app. For example, you should define animations, menus, styles, colors,
presentation of the app. For example, you can define animations, menus, styles, colors,
and the layout of activity user interfaces with XML files. Using app resources makes it easy
to update various characteristics of your app without modifying code and&mdash;by providing
sets of alternative resources&mdash;enables you to optimize your app for a variety of
device configurations (such as different languages and screen sizes).</p>
to update various characteristics of your app without modifying code. Providing
sets of alternative resources enables you to optimize your app for a variety of
device configurations, such as different languages and screen sizes.</p>
<p>For every resource that you include in your Android project, the SDK build tools define a unique
integer ID, which you can use to reference the resource from your app code or from
@@ -435,20 +476,22 @@ named {@code R.drawable.logo}, which you can use to reference the image and inse
user interface.</p>
<p>One of the most important aspects of providing resources separate from your source code
is the ability for you to provide alternative resources for different device
configurations. For example, by defining UI strings in XML, you can translate the strings into other
languages and save those strings in separate files. Then, based on a language <em>qualifier</em>
is the ability to provide alternative resources for different device
configurations. For example, by defining UI strings in XML, you can translate
the strings into other
languages and save those strings in separate files. Then Android applies the
appropriate language strings
to your UI based on a language <em>qualifier</em>
that you append to the resource directory's name (such as {@code res/values-fr/} for French string
values) and the user's language setting, the Android system applies the appropriate language strings
to your UI.</p>
values) and the user's language setting.</p>
<p>Android supports many different <em>qualifiers</em> for your alternative resources. The
qualifier is a short string that you include in the name of your resource directories in order to
define the device configuration for which those resources should be used. As another
example, you should often create different layouts for your activities, depending on the
device's screen orientation and size. For example, when the device screen is in portrait
define the device configuration for which those resources should be used. For
example, you should create different layouts for your activities, depending on the
device's screen orientation and size. When the device screen is in portrait
orientation (tall), you might want a layout with buttons to be vertical, but when the screen is in
landscape orientation (wide), the buttons should be aligned horizontally. To change the layout
landscape orientation (wide), the buttons could be aligned horizontally. To change the layout
depending on the orientation, you can define two different layouts and apply the appropriate
qualifier to each layout's directory name. Then, the system automatically applies the appropriate
layout depending on the current device orientation.</p>
@@ -465,15 +508,15 @@ create alternative resources for different device configurations, read <a href=
<dl>
<dt><a href="{@docRoot}guide/components/intents-filters.html">Intents and Intent Filters</a>
</dt>
<dd>Information about how to use the {@link android.content.Intent} APIs to
<dd>How to use the {@link android.content.Intent} APIs to
activate app components, such as activities and services, and how to make your app components
available for use by other apps.</dd>
<dt><a href="{@docRoot}guide/components/activities.html">Activities</a></dt>
<dd>Information about how to create an instance of the {@link android.app.Activity} class,
<dd>How to create an instance of the {@link android.app.Activity} class,
which provides a distinct screen in your application with a user interface.</dd>
<dt><a
href="{@docRoot}guide/topics/resources/providing-resources.html">Providing Resources</a></dt>
<dd>Information about how Android apps are structured to separate app resources from the
<dd>How Android apps are structured to separate app resources from the
app code, including how you can provide alternative resources for specific device
configurations.
</dd>
@@ -484,14 +527,13 @@ href="{@docRoot}guide/topics/resources/providing-resources.html">Providing Resou
<dl>
<dt><a href="{@docRoot}guide/practices/compatibility.html"
>Device Compatibility</a></dt>
<dd>Information about Android works on different types of devices and an introduction
<dd>How Android works on different types of devices and an introduction
to how you can optimize your app for each device or restrict your app's availability
to different devices.</dd>
<dt><a href="{@docRoot}guide/topics/security/permissions.html"
>System Permissions</a></dt>
<dd>Information about how Android restricts app access to certain APIs with a permission
<dd>How Android restricts app access to certain APIs with a permission
system that requires the user's consent for your app to use those APIs.</dd>
</dl>
</div>
</div>

292
docs/html/guide/components/intents-filters.jd
View File

@@ -7,21 +7,21 @@ page.tags="IntentFilter"
<h2>In this document</h2>
<ol>
<li><a href="#Types">Intent Types</a></li>
<li><a href="#Building">Building an Intent</a>
<li><a href="#Types">Intent types</a></li>
<li><a href="#Building">Building an intent</a>
<ol>
<li><a href="#ExampleExplicit">Example explicit intent</a></li>
<li><a href="#ExampleSend">Example implicit intent</a></li>
<li><a href="#ForceChooser">Forcing an app chooser</a></li>
</ol>
</li>
<li><a href="#Receiving">Receiving an Implicit Intent</a>
<li><a href="#Receiving">Receiving an implicit intent</a>
<ol>
<li><a href="#ExampleFilters">Example filters</a></li>
</ol>
</li>
<li><a href="#PendingIntent">Using a Pending Intent</a></li>
<li><a href="#Resolution">Intent Resolution</a>
<li><a href="#PendingIntent">Using a pending intent</a></li>
<li><a href="#Resolution">Intent resolution</a>
<ol>
<li><a href="#ActionTest">Action test</a></li>
<li><a href="#CategoryTest">Category test</a></li>
@@ -46,13 +46,14 @@ page.tags="IntentFilter"
<p>An {@link android.content.Intent} is a messaging object you can use to request an action
from another <a href="{@docRoot}guide/components/fundamentals.html#Components">app component</a>.
Although intents facilitate communication between components in several ways, there are three
fundamental use-cases:</p>
fundamental use cases:</p>
<ul>
<li><b>To start an activity:</b>
<li><b>Starting an activity</b>
<p>An {@link android.app.Activity} represents a single screen in an app. You can start a new
instance of an {@link android.app.Activity} by passing an {@link android.content.Intent}
to {@link android.content.Context#startActivity startActivity()}. The {@link android.content.Intent}
to {@link android.content.Context#startActivity startActivity()}.
The {@link android.content.Intent}
describes the activity to start and carries any necessary data.</p>
<p>If you want to receive a result from the activity when it finishes,
@@ -63,10 +64,16 @@ android.app.Activity#onActivityResult onActivityResult()} callback.
For more information, see the <a
href="{@docRoot}guide/components/activities.html">Activities</a> guide.</p></li>
<li><b>To start a service:</b>
<li><b>Starting a service</b>
<p>A {@link android.app.Service} is a component that performs operations in the background
without a user interface. You can start a service to perform a one-time operation
(such as download a file) by passing an {@link android.content.Intent}
without a user interface. With Android 5.0 (API level 21) and later, you can start a service
with {@link android.app.job.JobScheduler}. For more information
about {@link android.app.job.JobScheduler}, see its
{@link android.app.job.JobScheduler API-reference documentation}.</p>
<p>For versions earlier than Android 5.0 (API level 21), you can start a service by using
methods of the {@link android.app.Service} class. You can start a service
to perform a one-time operation
(such as downloading a file) by passing an {@link android.content.Intent}
to {@link android.content.Context#startService startService()}. The {@link android.content.Intent}
describes the service to start and carries any necessary data.</p>
@@ -75,7 +82,7 @@ from another component by passing an {@link android.content.Intent} to {@link
android.content.Context#bindService bindService()}</code>. For more information, see the <a
href="{@docRoot}guide/components/services.html">Services</a> guide.</p></li>
<li><b>To deliver a broadcast:</b>
<li><b>Delivering a broadcast</b>
<p>A broadcast is a message that any app can receive. The system delivers various
broadcasts for system events, such as when the system boots up or the device starts charging.
You can deliver a broadcast to other apps by passing an {@link android.content.Intent}
@@ -89,7 +96,7 @@ android.content.Context#sendStickyBroadcast sendStickyBroadcast()}.</p>
<h2 id="Types">Intent Types</h2>
<h2 id="Types">Intent types</h2>
<p>There are two types of intents:</p>
@@ -97,7 +104,7 @@ android.content.Context#sendStickyBroadcast sendStickyBroadcast()}.</p>
<li><b>Explicit intents</b> specify the component to start by name (the
fully-qualified class name). You'll typically use an explicit intent to start a component in
your own app, because you know the class name of the activity or service you want to start. For
example, start a new activity in response to a user action or start a service to download
example, you can start a new activity in response to a user action or start a service to download
a file in the background.</li>
<li><b>Implicit intents</b> do not name a specific component, but instead declare a general action
@@ -106,12 +113,13 @@ show the user a location on a map, you can use an implicit intent to request tha
app show a specified location on a map.</li>
</ul>
<p>When you create an explicit intent to start an activity or service, the system immediately
<p>Figure 1 shows how an intent is delivered to start an activity. When you create an
explicit intent to start an activity or service, the system immediately
starts the app component specified in the {@link android.content.Intent} object.</p>
<div class="figure" style="width:446px">
<img src="{@docRoot}images/components/intent-filters@2x.png" width="446" alt=""/>
<p class="img-caption"><strong>Figure 1.</strong> Illustration of how an implicit intent is
<p class="img-caption"><strong>Figure 1.</strong> How an implicit intent is
delivered through the system to start another activity: <b>[1]</b> <em>Activity A</em> creates an
{@link android.content.Intent} with an action description and passes it to {@link
android.content.Context#startActivity startActivity()}. <b>[2]</b> The Android System searches all
@@ -135,11 +143,12 @@ you make it possible for other apps to directly start your activity with a certa
Likewise, if you do <em>not</em> declare any intent filters for an activity, then it can be started
only with an explicit intent.</p>
<p class="caution"><strong>Caution:</strong> To ensure your app is secure, always use an explicit
<p class="caution"><strong>Caution:</strong> To ensure that your app is secure, always
use an explicit
intent when starting a {@link android.app.Service} and do not
declare intent filters for your services. Using an implicit intent to start a service is a
security hazard because you cannot be certain what service will respond to the intent,
and the user cannot see which service starts. Beginning with Android 5.0 (API level 21), the system
security hazard because you can't be certain what service will respond to the intent,
and the user can't see which service starts. Beginning with Android 5.0 (API level 21), the system
throws an exception if you call {@link android.content.Context#bindService bindService()}
with an implicit intent.</p>
@@ -147,7 +156,7 @@ with an implicit intent.</p>
<h2 id="Building">Building an Intent</h2>
<h2 id="Building">Building an intent</h2>
<p>An {@link android.content.Intent} object carries information that the Android system uses
to determine which component to start (such as the exact component name or component
@@ -163,22 +172,23 @@ order to properly perform the action (such as the action to take and the data to
<dd>The name of the component to start.
<p>This is optional, but it's the critical piece of information that makes an intent
<b>explicit</b>, meaning that the intent should be delivered only to the app component
defined by the component name. Without a component name, the intent is <b>implicit</b> and the
<em>explicit</em>, meaning that the intent should be delivered only to the app component
defined by the component name. Without a component name, the intent is <em>implicit</em> and the
system decides which component should receive the intent based on the other intent information
(such as the action, data, and category&mdash;described below). So if you need to start a specific
(such as the action, data, and category&mdash;described below). If you need to start a specific
component in your app, you should specify the component name.</p>
<p class="note"><strong>Note:</strong> When starting a {@link android.app.Service}, you should
<strong>always specify the component name</strong>. Otherwise, you cannot be certain what service
<p class="note"><strong>Note:</strong> When starting a {@link android.app.Service},
<em>always specify the component name</em>. Otherwise, you cannot be certain what service
will respond to the intent, and the user cannot see which service starts.</p>
<p>This field of the {@link android.content.Intent} is a
{@link android.content.ComponentName} object, which you can specify using a fully
qualified class name of the target component, including the package name of the app. For example,
qualified class name of the target component, including the package name of the app, for example,
{@code com.example.ExampleActivity}. You can set the component name with {@link
android.content.Intent#setComponent setComponent()}, {@link android.content.Intent#setClass
setClass()}, {@link android.content.Intent#setClassName(String, String) setClassName()}, or with the
setClass()}, {@link android.content.Intent#setClassName(String, String) setClassName()},
or with the
{@link android.content.Intent} constructor.</p>
</dd>
@@ -188,10 +198,10 @@ setClass()}, {@link android.content.Intent#setClassName(String, String) setClass
<p>In the case of a broadcast intent, this is the action that took place and is being reported.
The action largely determines how the rest of the intent is structured&mdash;particularly
what is contained in the data and extras.
the information that is contained in the data and extras.
<p>You can specify your own actions for use by intents within your app (or for use by other
apps to invoke components in your app), but you should usually use action constants
apps to invoke components in your app), but you usually specify action constants
defined by the {@link android.content.Intent} class or other framework classes. Here are some
common actions for starting an activity:</p>
@@ -203,7 +213,7 @@ common actions for starting an activity:</p>
view in a map app.</dd>
<dt>{@link android.content.Intent#ACTION_SEND}</dt>
<dd>Also known as the "share" intent, you should use this in an intent with {@link
<dd>Also known as the <em>share</em> intent, you should use this in an intent with {@link
android.content.Context#startActivity startActivity()} when you have some data that the user can
share through another app, such as an email app or social sharing app.</dd>
</dl>
@@ -217,12 +227,13 @@ that open specific screens in the system's Settings app.</p>
setAction()} or with an {@link android.content.Intent} constructor.</p>
<p>If you define your own actions, be sure to include your app's package name
as a prefix. For example:</p>
as a prefix, as shown in the following example:</p>
<pre>static final String ACTION_TIMETRAVEL = "com.example.action.TIMETRAVEL";</pre>
</dd>
<dt><b>Data</b></dt>
<dd>The URI (a {@link android.net.Uri} object) that references the data to be acted on and/or the
<dd>The URI (a {@link android.net.Uri} object) that references the data to
be acted on and/or the
MIME type of that data. The type of data supplied is generally dictated by the intent's action. For
example, if the action is {@link android.content.Intent#ACTION_EDIT}, the data should contain the
URI of the document to edit.
@@ -231,10 +242,11 @@ URI of the document to edit.
it's often important to specify the type of data (its MIME type) in addition to its URI.
For example, an activity that's able to display images probably won't be able
to play an audio file, even though the URI formats could be similar.
So specifying the MIME type of your data helps the Android
Specifying the MIME type of your data helps the Android
system find the best component to receive your intent.
However, the MIME type can sometimes be inferred from the URI&mdash;particularly when the data is a
{@code content:} URI, which indicates the data is located on the device and controlled by a
{@code content:} URI. A {@code content:} URI indicates the data is located on the device
and controlled by a
{@link android.content.ContentProvider}, which makes the data MIME type visible to the system.</p>
<p>To set only the data URI, call {@link android.content.Intent#setData setData()}.
@@ -243,7 +255,7 @@ can set both explicitly with {@link
android.content.Intent#setDataAndType setDataAndType()}.</p>
<p class="caution"><strong>Caution:</strong> If you want to set both the URI and MIME type,
<strong>do not</strong> call {@link android.content.Intent#setData setData()} and
<em>don't</em> call {@link android.content.Intent#setData setData()} and
{@link android.content.Intent#setType setType()} because they each nullify the value of the other.
Always use {@link android.content.Intent#setDataAndType setDataAndType()} to set both
URI and MIME type.</p>
@@ -258,7 +270,7 @@ Here are some common categories:
<dl>
<dt>{@link android.content.Intent#CATEGORY_BROWSABLE}</dt>
<dd>The target activity allows itself to be started by a web browser to display data
referenced by a link&mdash;such as an image or an e-mail message.
referenced by a link, such as an image or an e-mail message.
</dd>
<dt>{@link android.content.Intent#CATEGORY_LAUNCHER}</dt>
<dd>The activity is the initial activity of a task and is listed in
@@ -276,14 +288,14 @@ categories.</p>
<p>These properties listed above (component name, action, data, and category) represent the
defining characteristics of an intent. By reading these properties, the Android system
is able to resolve which app component it should start.</p>
<p>However, an intent can carry additional information that does not affect
how it is resolved to an app component. An intent can also supply:</p>
is able to resolve which app component it should start. However, an intent can carry
additional information that does not affect
how it is resolved to an app component. An intent can also supply the following information:</p>
<dl>
<dt><b>Extras</b></dt>
<dd>Key-value pairs that carry additional information required to accomplish the requested action.
<dd>Key-value pairs that carry additional information required to accomplish
the requested action.
Just as some actions use particular kinds of data URIs, some actions also use particular extras.
<p>You can add extra data with various {@link android.content.Intent#putExtra putExtra()} methods,
@@ -293,21 +305,22 @@ the {@link android.os.Bundle} in the {@link android.content.Intent} with {@link
android.content.Intent#putExtras putExtras()}.</p>
<p>For example, when creating an intent to send an email with
{@link android.content.Intent#ACTION_SEND}, you can specify the "to" recipient with the
{@link android.content.Intent#EXTRA_EMAIL} key, and specify the "subject" with the
{@link android.content.Intent#ACTION_SEND}, you can specify the <em>to</em> recipient with the
{@link android.content.Intent#EXTRA_EMAIL} key, and specify the <em>subject</em> with the
{@link android.content.Intent#EXTRA_SUBJECT} key.</p>
<p>The {@link android.content.Intent} class specifies many {@code EXTRA_*} constants
for standardized data types. If you need to declare your own extra keys (for intents that
your app receives), be sure to include your app's package name
as a prefix. For example:</p>
as a prefix, as shown in the following example:</p>
<pre>static final String EXTRA_GIGAWATTS = "com.example.EXTRA_GIGAWATTS";</pre>
</dd>
<dt><b>Flags</b></dt>
<dd>Flags defined in the {@link android.content.Intent} class that function as metadata for the
<dd>Flags are defined in the {@link android.content.Intent} class that function as metadata for the
intent. The flags may instruct the Android system how to launch an activity (for example, which
<a href="{@docRoot}guide/components/tasks-and-back-stack.html">task</a> the activity should belong
<a href="{@docRoot}guide/components/tasks-and-back-stack.html">task</a>
the activity should belong
to) and how to treat it after it's launched (for example, whether it belongs in the list of recent
activities).
@@ -354,7 +367,8 @@ this intent explicitly starts the {@code DownloadService} class in the app.</p>
to perform the action. Using an implicit intent is useful when your app cannot perform the
action, but other apps probably can and you'd like the user to pick which app to use.</p>
<p>For example, if you have content you want the user to share with other people, create an intent
<p>For example, if you have content that you want the user to share with other people,
create an intent
with the {@link android.content.Intent#ACTION_SEND} action
and add extras that specify the content to share. When you call
{@link android.content.Context#startActivity startActivity()} with that intent, the user can
@@ -362,13 +376,15 @@ pick an app through which to share the content.</p>
<p class="caution"><strong>Caution:</strong> It's possible that a user won't have <em>any</em>
apps that handle the implicit intent you send to {@link android.content.Context#startActivity
startActivity()}. If that happens, the call will fail and your app will crash. To verify
startActivity()}. If that happens, the call fails and your app crashes. To verify
that an activity will receive the intent, call {@link android.content.Intent#resolveActivity
resolveActivity()} on your {@link android.content.Intent} object. If the result is non-null,
then there is at least one app that can handle the intent and it's safe to call
there is at least one app that can handle the intent and it's safe to call
{@link android.content.Context#startActivity startActivity()}. If the result is null,
you should not use the intent and, if possible, you should disable the feature that issues
the intent.</p>
do not use the intent and, if possible, you should disable the feature that issues
the intent. The following example shows how to verify that the intent resolves
to an activity. This example doesn't use a URI, but the intent's data type
is declared to specify the content carried by the extras.</p>
<pre>
@@ -384,8 +400,7 @@ if (sendIntent.resolveActivity(getPackageManager()) != null) {
}
</pre>
<p class="note"><strong>Note:</strong> In this case, a URI is not used, but the intent's data type
is declared to specify the content carried by the extras.</p>
<p>When {@link android.content.Context#startActivity startActivity()} is called, the system
@@ -393,7 +408,7 @@ examines all of the installed apps to determine which ones can handle this kind
intent with the {@link android.content.Intent#ACTION_SEND} action and that carries "text/plain"
data). If there's only one app that can handle it, that app opens immediately and is given the
intent. If multiple activities accept the intent, the system
displays a dialog so the user can pick which app to use..</p>
displays a dialog such as the one shown in Figure 2, so the user can pick which app to use.</p>
<div class="figure" style="width:200px">
@@ -405,23 +420,26 @@ displays a dialog so the user can pick which app to use..</p>
<p>When there is more than one app that responds to your implicit intent,
the user can select which app to use and make that app the default choice for the
action. This is nice when performing an action for which the user
probably wants to use the same app from now on, such as when opening a web page (users
often prefer just one web browser) .</p>
action. The ability to select a default is helpful when performing an action for which the user
probably wants to use the same app every time, such as when opening a web page (users
often prefer just one web browser).</p>
<p>However, if multiple apps can respond to the intent and the user might want to use a different
app each time, you should explicitly show a chooser dialog. The chooser dialog asks the
user to select which app to use for the action every time (the user cannot select a default app for
user to select which app to use for the action (the user cannot select a default app for
the action). For example, when your app performs "share" with the {@link
android.content.Intent#ACTION_SEND} action, users may want to share using a different app depending
on their current situation, so you should always use the chooser dialog, as shown in figure 2.</p>
on their current situation, so you should always use the chooser dialog, as shown in Figure 2.</p>
<p>To show the chooser, create an {@link android.content.Intent} using {@link
android.content.Intent#createChooser createChooser()} and pass it to {@link
android.app.Activity#startActivity startActivity()}. For example:</p>
android.app.Activity#startActivity startActivity()}, as shown in the following example.
This example displays a dialog with a list of apps that respond to the intent passed to the {@link
android.content.Intent#createChooser createChooser()} method and uses the supplied text as the
dialog title.</p>
<pre>
Intent sendIntent = new Intent(Intent.ACTION_SEND);
@@ -439,26 +457,16 @@ if (sendIntent.resolveActivity(getPackageManager()) != null) {
}
</pre>
<p>This displays a dialog with a list of apps that respond to the intent passed to the {@link
android.content.Intent#createChooser createChooser()} method and uses the supplied text as the
dialog title.</p>
<h2 id="Receiving">Receiving an Implicit Intent</h2>
<h2 id="Receiving">Receiving an implicit intent</h2>
<p>To advertise which implicit intents your app can receive, declare one or more intent filters for
each of your app components with an <a href=
"{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code <intent-filter>}</a>
"{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code &lt;intent-filter&gt;}</a>
element in your <a href="{@docRoot}guide/topics/manifest/manifest-intro.html">manifest file</a>.
Each intent filter specifies the type of intents it accepts based on the intent's action,
data, and category. The system will deliver an implicit intent to your app component only if the
data, and category. The system delivers an implicit intent to your app component only if the
intent can pass through one of your intent filters.</p>
<p class="note"><strong>Note:</strong> An explicit intent is always delivered to its target,
@@ -471,28 +479,28 @@ it inspects the {@link android.content.Intent} and decides how to behave based o
in the {@link android.content.Intent} (such as to show the editor controls or not).</p>
<p>Each intent filter is defined by an <a
href="{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code <intent-filter>}</a>
href="{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code &lt;intent-filter>}</a>
element in the app's manifest file, nested in the corresponding app component (such
as an <a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code <activity>}</a>
as an <a href="{@docRoot}guide/topics/manifest/activity-element.html">{@code &lt;activity>}</a>
element). Inside the <a
href="{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code <intent-filter>}</a>,
href="{@docRoot}guide/topics/manifest/intent-filter-element.html">{@code &lt;intent-filter>}</a>,
you can specify the type of intents to accept using one or more
of these three elements:</p>
<dl>
<dt><a href="{@docRoot}guide/topics/manifest/action-element.html">{@code <action>}</a></dt>
<dt><a href="{@docRoot}guide/topics/manifest/action-element.html">{@code &lt;action>}</a></dt>
<dd>Declares the intent action accepted, in the {@code name} attribute. The value
must be the literal string value of an action, not the class constant.</dd>
<dt><a href="{@docRoot}guide/topics/manifest/data-element.html">{@code <data>}</a></dt>
<dt><a href="{@docRoot}guide/topics/manifest/data-element.html">{@code &lt;data>}</a></dt>
<dd>Declares the type of data accepted, using one or more attributes that specify various
aspects of the data URI (<code>scheme</code>, <code>host</code>, <code>port</code>,
<code>path</code>, etc.) and MIME type.</dd>
<dt><a href="{@docRoot}guide/topics/manifest/category-element.html">{@code <category>}</a></dt>
<code>path</code>) and MIME type.</dd>
<dt><a href="{@docRoot}guide/topics/manifest/category-element.html">{@code &lt;category>}</a></dt>
<dd>Declares the intent category accepted, in the {@code name} attribute. The value
must be the literal string value of an action, not the class constant.
<p class="note"><strong>Note:</strong> In order to receive implicit intents, you
<strong>must include</strong> the
<p class="note"><strong>Note:</strong> To receive implicit intents, you
<em>must include</em> the
{@link android.content.Intent#CATEGORY_DEFAULT} category in the intent filter. The methods
{@link android.app.Activity#startActivity startActivity()} and
{@link android.app.Activity#startActivityForResult startActivityForResult()} treat all intents
@@ -515,12 +523,12 @@ of these three elements:</p>
&lt;/activity>
</pre>
<p>It's okay to create a filter that includes more than one instance of
<a href="{@docRoot}guide/topics/manifest/action-element.html">{@code <action>}</a>,
<a href="{@docRoot}guide/topics/manifest/data-element.html">{@code <data>}</a>, or
<a href="{@docRoot}guide/topics/manifest/category-element.html">{@code <category>}</a>.
If you do, you simply need to be certain that the component can handle any and all combinations
of those filter elements.</p>
<p>You can create a filter that includes more than one instance of
<a href="{@docRoot}guide/topics/manifest/action-element.html">{@code &lt;action>}</a>,
<a href="{@docRoot}guide/topics/manifest/data-element.html">{@code &lt;data>}</a>, or
<a href="{@docRoot}guide/topics/manifest/category-element.html">{@code &lt;category>}</a>.
If you do, you need to be certain that the component can handle any and all
combinations of those filter elements.</p>
<p>When you want to handle multiple kinds of intents, but only in specific combinations of
action, data, and category type, then you need to create multiple intent filters.</p>
@@ -569,8 +577,8 @@ is running.</p>
<h3 id="ExampleFilters">Example filters</h3>
<p>To better understand some of the intent filter behaviors, look at the following snippet
from the manifest file of a social-sharing app.</p>
<p>To demonstrate some of the intent filter behaviors, here is an example
from the manifest file of a social-sharing app:</p>
<pre>
&lt;activity android:name="MainActivity">
@@ -607,9 +615,9 @@ opens when the user initially launches the app with the launcher icon:</p>
indicates this is the main entry point and does not expect any intent data.</li>
<li>The {@link android.content.Intent#CATEGORY_LAUNCHER} category indicates that this activity's
icon should be placed in the system's app launcher. If the <a
href="{@docRoot}guide/topics/manifest/activity-element.html">{@code <activity>}</a> element
href="{@docRoot}guide/topics/manifest/activity-element.html">{@code &lt;activity>}</a> element
does not specify an icon with {@code icon}, then the system uses the icon from the <a
href="{@docRoot}guide/topics/manifest/application-element.html">{@code <application>}</a>
href="{@docRoot}guide/topics/manifest/application-element.html">{@code &lt;application>}</a>
element.</li>
</ul>
<p>These two must be paired together in order for the activity to appear in the app launcher.</p>
@@ -620,7 +628,7 @@ they can also enter {@code ShareActivity} directly from another app that issues
intent matching one of the two intent filters.</p>
<p class="note"><strong>Note:</strong> The MIME type,
<a href="https://developers.google.com/panorama/android/">{@code
<a href="https://developers.google.com/panorama/android/" class="external-link">{@code
application/vnd.google.panorama360+jpg}</a>, is a special data type that specifies
panoramic photos, which you can handle with the <a
href="{@docRoot}reference/com/google/android/gms/panorama/package-summary.html">Google
@@ -638,7 +646,7 @@ panorama</a> APIs.</p>
<h2 id="PendingIntent">Using a Pending Intent</h2>
<h2 id="PendingIntent">Using a pending intent</h2>
<p>A {@link android.app.PendingIntent} object is a wrapper around an {@link
android.content.Intent} object. The primary purpose of a {@link android.app.PendingIntent}
@@ -646,25 +654,25 @@ is to grant permission to a foreign application
to use the contained {@link android.content.Intent} as if it were executed from your
app's own process.</p>
<p>Major use cases for a pending intent include:</p>
<p>Major use cases for a pending intent include the following:</p>
<ul>
<li>Declare an intent to be executed when the user performs an action with your <a
<li>Declaring an intent to be executed when the user performs an action with your <a
href="{@docRoot}guide/topics/ui/notifiers/notifications.html">Notification</a>
(the Android system's {@link android.app.NotificationManager}
executes the {@link android.content.Intent}).
<li>Declare an intent to be executed when the user performs an action with your
<li>Declaring an intent to be executed when the user performs an action with your
<a href="{@docRoot}guide/topics/appwidgets/index.html">App Widget</a>
(the Home screen app executes the {@link android.content.Intent}).
<li>Declare an intent to be executed at a specified time in the future (the Android
<li>Declaring an intent to be executed at a specified future time (the Android
system's {@link android.app.AlarmManager} executes the {@link android.content.Intent}).
</ul>
<p>Because each {@link android.content.Intent} object is designed to be handled by a specific
<p>Just as each {@link android.content.Intent} object is designed to be handled by a specific
type of app component (either an {@link android.app.Activity}, a {@link android.app.Service}, or
a {@link android.content.BroadcastReceiver}), so too must a {@link android.app.PendingIntent} be
created with the same consideration. When using a pending intent, your app will not
created with the same consideration. When using a pending intent, your app doesn't
execute the intent with a call such as {@link android.content.Context#startActivity
startActivity()}. You must instead declare the intended component type when you create the
startActivity()}. Instead, you must declare the intended component type when you create the
{@link android.app.PendingIntent} by calling the respective creator method:</p>
<ul>
@@ -677,14 +685,14 @@ startActivity()}. You must instead declare the intended component type when you
</ul>
<p>Unless your app is <em>receiving</em> pending intents from other apps,
the above methods to create a {@link android.app.PendingIntent} are the only
{@link android.app.PendingIntent} methods you'll probably ever need.</p>
the above methods to create a {@link android.app.PendingIntent} are probably the only
{@link android.app.PendingIntent} methods you'll ever need.</p>
<p>Each method takes the current app {@link android.content.Context}, the
{@link android.content.Intent} you want to wrap, and one or more flags that specify
how the intent should be used (such as whether the intent can be used more than once).</p>
<p>More information about using pending intents is provided with the documentation for each
<p>For more information about using pending intents, see the documentation for each
of the respective use cases, such as in the <a
href="{@docRoot}guide/topics/ui/notifiers/notifications.html">Notifications</a>
and <a href="{@docRoot}guide/topics/appwidgets/index.html">App Widgets</a> API guides.</p>
@@ -695,27 +703,27 @@ and <a href="{@docRoot}guide/topics/appwidgets/index.html">App Widgets</a> API g
<h2 id="Resolution">Intent Resolution</h2>
<h2 id="Resolution">Intent resolution</h2>
<p>When the system receives an implicit intent to start an activity, it searches for the
best activity for the intent by comparing the intent to intent filters based on three aspects:</p>
best activity for the intent by comparing the it to intent filters based on three aspects:</p>
<ul>
<li>The intent action
<li>The intent data (both URI and data type)
<li>The intent category
<li>Action.
<li>Data (both URI and data type).
<li>Category.
</ul>
<p>The following sections describe how intents are matched to the appropriate component(s)
in terms of how the intent filter is declared in an app's manifest file.</p>
<p>The following sections describe how intents are matched to the appropriate components
according to the intent filter declaration in an app's manifest file.</p>
<h3 id="ActionTest">Action test</h3>
<p>To specify accepted intent actions, an intent filter can declare zero or more
<a href="{@docRoot}guide/topics/manifest/action-element.html">{@code
<action>}</a> elements. For example:</p>
&lt;action&gt;}</a> elements, as shown in the following example:</p>
<pre>
&lt;intent-filter&gt;
@@ -725,13 +733,13 @@ in terms of how the intent filter is declared in an app's manifest file.</p>
&lt;/intent-filter&gt;
</pre>
<p>To get through this filter, the action specified in the {@link android.content.Intent}
<p>To pass this filter, the action specified in the {@link android.content.Intent}
must match one of the actions listed in the filter.</p>
<p>If the filter does not list any actions, there is nothing for an
intent to match, so all intents fail the test. However, if an {@link android.content.Intent}
does not specify an action, it will pass the test (as long as the filter
contains at least one action).</p>
does not specify an action, it passes the test as long as the filter
contains at least one action.</p>
@@ -739,7 +747,7 @@ contains at least one action).</p>
<p>To specify accepted intent categories, an intent filter can declare zero or more
<a href="{@docRoot}guide/topics/manifest/category-element.html">{@code
<category>}</a> elements. For example:</p>
<category>}</a> elements, as shown in the following example:</p>
<pre>
&lt;intent-filter&gt;
@@ -752,17 +760,17 @@ contains at least one action).</p>
<p>For an intent to pass the category test, every category in the {@link android.content.Intent}
must match a category in the filter. The reverse is not necessary&mdash;the intent filter may
declare more categories than are specified in the {@link android.content.Intent} and the
{@link android.content.Intent} will still pass. Therefore, an intent with no categories should
always pass this test, regardless of what categories are declared in the filter.</p>
{@link android.content.Intent} still passes. Therefore, an intent with no categories
always passes this test, regardless of what categories are declared in the filter.</p>
<p class="note"><strong>Note:</strong>
Android automatically applies the the {@link android.content.Intent#CATEGORY_DEFAULT} category
Android automatically applies the {@link android.content.Intent#CATEGORY_DEFAULT} category
to all implicit intents passed to {@link
android.content.Context#startActivity startActivity()} and {@link
android.app.Activity#startActivityForResult startActivityForResult()}.
So if you want your activity to receive implicit intents, it must
include a category for {@code "android.intent.category.DEFAULT"} in its intent filters (as
shown in the previous {@code <intent-filter>} example.</p>
If you want your activity to receive implicit intents, it must
include a category for {@code "android.intent.category.DEFAULT"} in its intent filters, as
shown in the previous {@code &lt;intent-filter>} example.</p>
@@ -770,7 +778,7 @@ shown in the previous {@code <intent-filter>} example.</p>
<p>To specify accepted intent data, an intent filter can declare zero or more
<a href="{@docRoot}guide/topics/manifest/data-element.html">{@code
<data>}</a> elements. For example:</p>
&lt;data&gt;}</a> elements, as shown in the following example:</p>
<pre>
&lt;intent-filter&gt;
@@ -781,15 +789,16 @@ shown in the previous {@code <intent-filter>} example.</p>
</pre>
<p>Each <code><a href="{@docRoot}guide/topics/manifest/data-element.html">&lt;data&gt;</a></code>
element can specify a URI structure and a data type (MIME media type). There are separate
attributes &mdash; {@code scheme}, {@code host}, {@code port},
and {@code path} &mdash; for each part of the URI:
element can specify a URI structure and a data type (MIME media type).
Each part of the URI is a separate
attribute: {@code scheme}, {@code host}, {@code port},
and {@code path}:
</p>
<p style="margin-left: 2em">{@code <scheme>://<host>:<port>/<path>}</p>
<p style="margin-left: 2em">{@code &lt;scheme>://&lt;host>:&lt;port>/&lt;path>}</p>
<p>
For example:
The following example shows possible values for these attributes:
</p>
<p style="margin-left: 2em">{@code content://com.example.project:200/folder/subfolder/etc}</p>
@@ -799,7 +808,7 @@ the port is {@code 200}, and the path is {@code folder/subfolder/etc}.
</p>
<p>Each of these attributes is optional in a <a
href="{@docRoot}guide/topics/manifest/data-element.html">{@code <data>}</a> element,
href="{@docRoot}guide/topics/manifest/data-element.html">{@code &lt;data>}</a> element,
but there are linear dependencies:</p>
<ul>
<li>If a scheme is not specified, the host is ignored.</li>
@@ -842,17 +851,17 @@ type matches a type listed in the filter. It passes the URI part of the test
either if its URI matches a URI in the filter or if it has a {@code content:}
or {@code file:} URI and the filter does not specify a URI. In other words,
a component is presumed to support {@code content:} and {@code file:} data if
its filter lists <em>only</em> a MIME type.</p></li>
its filter lists <em>only</em> a MIME type.</li>
</ol>
<p>
This last rule, rule (d), reflects the expectation
that components are able to get local data from a file or content provider.
Therefore, their filters can list just a data type and do not need to explicitly
Therefore, their filters can list just a data type and don't need to explicitly
name the {@code content:} and {@code file:} schemes.
This is a typical case. A <a
href="{@docRoot}guide/topics/manifest/data-element.html">{@code <data>}</a> element
like the following, for example, tells Android that the component can get image data from a content
The following example shows a typical case in which a <a
href="{@docRoot}guide/topics/manifest/data-element.html">{@code &lt;data>}</a> element
tells Android that the component can get image data from a content
provider and display it:
</p>
@@ -863,14 +872,15 @@ provider and display it:
&lt;/intent-filter&gt;</pre>
<p>
Because most available data is dispensed by content providers, filters that
specify a data type but not a URI are perhaps the most common.
Filters that
specify a data type but not a URI are perhaps the most common because most available
data is dispensed by content providers.
</p>
<p>
Another common configuration is filters with a scheme and a data type. For
Another common configuration is a filter with a scheme and a data type. For
example, a <a
href="{@docRoot}guide/topics/manifest/data-element.html">{@code <data>}</a>
href="{@docRoot}guide/topics/manifest/data-element.html">{@code &lt;data>}</a>
element like the following tells Android that
the component can retrieve video data from the network in order to perform the action:
</p>
@@ -894,7 +904,7 @@ by finding all the activities with intent filters that specify the
<p>Your application can use intent matching in a similar way.
The {@link android.content.pm.PackageManager} has a set of {@code query...()}
methods that return all components that can accept a particular intent, and
methods that return all components that can accept a particular intent and
a similar series of {@code resolve...()} methods that determine the best
component to respond to an intent. For example,
{@link android.content.pm.PackageManager#queryIntentActivities
@@ -907,7 +917,3 @@ can respond. There's a similar method,
{@link android.content.pm.PackageManager#queryBroadcastReceivers
queryBroadcastReceivers()}, for broadcast receivers.
</p>

517
docs/html/guide/components/services.jd
View File

@@ -5,11 +5,11 @@ page.title=Services
<ol id="qv">
<h2>In this document</h2>
<ol>
<li><a href="#Basics">The Basics</a></li>
<li><a href="#Basics">The basics</a></li>
<ol>
<li><a href="#Declaring">Declaring a service in the manifest</a></li>
</ol>
<li><a href="#CreatingAService">Creating a Started Service</a>
<li><a href="#CreatingAService">Creating a started service</a>
<ol>
<li><a href="#ExtendingIntentService">Extending the IntentService class</a></li>
<li><a href="#ExtendingService">Extending the Service class</a></li>
@@ -17,10 +17,10 @@ page.title=Services
<li><a href="#Stopping">Stopping a service</a></li>
</ol>
</li>
<li><a href="#CreatingBoundService">Creating a Bound Service</a></li>
<li><a href="#Notifications">Sending Notifications to the User</a></li>
<li><a href="#Foreground">Running a Service in the Foreground</a></li>
<li><a href="#Lifecycle">Managing the Lifecycle of a Service</a>
<li><a href="#CreatingBoundService">Creating a bound service</a></li>
<li><a href="#Notifications">Sending notifications to the user</a></li>
<li><a href="#Foreground">Running a service in the foreground</a></li>
<li><a href="#Lifecycle">Managing the lifecycle of a service</a>
<ol>
<li><a href="#LifecycleCallbacks">Implementing the lifecycle callbacks</a></li>
</ol>
@@ -48,70 +48,80 @@ page.title=Services
</div>
<p>A {@link android.app.Service} is an application component that can perform
long-running operations in the background and does not provide a user interface. Another
application component can start a service and it will continue to run in the background even if the
long-running operations in the background, and it does not provide a user interface. Another
application component can start a service, and it continues to run in the background even if the
user switches to another application. Additionally, a component can bind to a service to
interact with it and even perform interprocess communication (IPC). For example, a service might
interact with it and even perform interprocess communication (IPC). For example, a service can
handle network transactions, play music, perform file I/O, or interact with a content provider, all
from the background.</p>
<p>A service can essentially take two forms:</p>
<p>These are the three different types of services:</p>
<dl>
<dt>Scheduled</dt>
<dd>A service is <em>scheduled</em> when an API such as the {@link android.app.job.JobScheduler},
introduced in Android 5.0 (API level 21), launches the service. You can use the
{@link android.app.job.JobScheduler} by registering jobs and specifying their requirements for
network and timing. The system then gracefully schedules the jobs for execution at the
appropriate times. The {@link android.app.job.JobScheduler} provides many methods to define
service-execution conditions.
<p class="note"><strong>Note:</strong> If your app targets Android 5.0 (API level 21), Google
recommends that you use the {@link android.app.job.JobScheduler} to execute background
services. For more information about using this class, see the
{@link android.app.job.JobScheduler} reference documentation.</p></dd>
<dt>Started</dt>
<dd>A service is "started" when an application component (such as an activity) starts it by
calling {@link android.content.Context#startService startService()}. Once started, a service
can run in the background indefinitely, even if the component that started it is destroyed. Usually,
a started service performs a single operation and does not return a result to the caller.
For example, it might download or upload a file over the network. When the operation is done, the
service should stop itself.</dd>
<dd>A service is <em>started</em> when an application component (such as an activity)
calls {@link android.content.Context#startService startService()}. After it's started, a
service can run in the background indefinitely, even if the component that started it is
destroyed. Usually, a started service performs a single operation and does not return a result to
the caller. For example, it can download or upload a file over the network. When the operation is
complete, the service should stop itself.</dd>
<dt>Bound</dt>
<dd>A service is "bound" when an application component binds to it by calling {@link
android.content.Context#bindService bindService()}. A bound service offers a client-server
interface that allows components to interact with the service, send requests, get results, and even
do so across processes with interprocess communication (IPC). A bound service runs only as long as
another application component is bound to it. Multiple components can bind to the service at once,
but when all of them unbind, the service is destroyed.</dd>
<dd>A service is <em>bound</em> when an application component binds to it by calling {@link
android.content.Context#bindService bindService()}. A bound service offers a client-server
interface that allows components to interact with the service, send requests, receive results,
and even do so across processes with interprocess communication (IPC). A bound service runs only
as long as another application component is bound to it. Multiple components can bind to the
service at once, but when all of them unbind, the service is destroyed.</dd>
</dl>
<p>Although this documentation generally discusses these two types of services separately, your
service can work both ways&mdash;it can be started (to run indefinitely) and also allow binding.
It's simply a matter of whether you implement a couple callback methods: {@link
<p>Although this documentation generally discusses started and bound services separately,
your service can work both ways&mdash;it can be started (to run indefinitely) and also allow
binding. It's simply a matter of whether you implement a couple of callback methods: {@link
android.app.Service#onStartCommand onStartCommand()} to allow components to start it and {@link
android.app.Service#onBind onBind()} to allow binding.</p>
<p>Regardless of whether your application is started, bound, or both, any application component
can use the service (even from a separate application), in the same way that any component can use
can use the service (even from a separate application) in the same way that any component can use
an activity&mdash;by starting it with an {@link android.content.Intent}. However, you can declare
the service as private, in the manifest file, and block access from other applications. This is
discussed more in the section about <a href="#Declaring">Declaring the service in the
the service as <em>private</em> in the manifest file and block access from other applications.
This is discussed more in the section about <a href="#Declaring">Declaring the service in the
manifest</a>.</p>
<p class="caution"><strong>Caution:</strong> A service runs in the
main thread of its hosting process&mdash;the service does <strong>not</strong> create its own thread
and does <strong>not</strong> run in a separate process (unless you specify otherwise). This means
that, if your service is going to do any CPU intensive work or blocking operations (such as MP3
playback or networking), you should create a new thread within the service to do that work. By using
a separate thread, you will reduce the risk of Application Not Responding (ANR) errors and the
application's main thread can remain dedicated to user interaction with your activities.</p>
main thread of its hosting process; the service does <strong>not</strong> create its own
thread and does <strong>not</strong> run in a separate process unless you specify otherwise. If
your service is going to perform any CPU-intensive work or blocking operations, such as MP3
playback or networking, you should create a new thread within the service to complete that work.
By using a separate thread, you can reduce the risk of Application Not Responding (ANR) errors,
and the application's main thread can remain dedicated to user interaction with your
activities.</p>
<h2 id="Basics">The Basics</h2>
<h2 id="Basics">The basics</h2>
<div class="sidebox-wrapper">
<div class="sidebox">
<h3>Should you use a service or a thread?</h3>
<p>A service is simply a component that can run in the background even when the user is not
interacting with your application. Thus, you should create a service only if that is what you
<p>A service is simply a component that can run in the background, even when the user is not
interacting with your application, so you should create a service only if that is what you
need.</p>
<p>If you need to perform work outside your main thread, but only while the user is interacting
with your application, then you should probably instead create a new thread and not a service. For
example, if you want to play some music, but only while your activity is running, you might create
<p>If you must perform work outside of your main thread, but only while the user is interacting
with your application, you should instead create a new thread. For example, if you want to
play some music, but only while your activity is running, you might create
a thread in {@link android.app.Activity#onCreate onCreate()}, start running it in {@link
android.app.Activity#onStart onStart()}, then stop it in {@link android.app.Activity#onStop
onStop()}. Also consider using {@link android.os.AsyncTask} or {@link android.os.HandlerThread},
android.app.Activity#onStart onStart()}, and stop it in {@link android.app.Activity#onStop
onStop()}. Also consider using {@link android.os.AsyncTask} or {@link android.os.HandlerThread}
instead of the traditional {@link java.lang.Thread} class. See the <a
href="{@docRoot}guide/components/processes-and-threads.html#Threads">Processes and
Threading</a> document for more information about threads.</p>
@@ -121,78 +131,81 @@ blocking operations.</p>
</div>
</div>
<p>To create a service, you must create a subclass of {@link android.app.Service} (or one
of its existing subclasses). In your implementation, you need to override some callback methods that
handle key aspects of the service lifecycle and provide a mechanism for components to bind to
the service, if appropriate. The most important callback methods you should override are:</p>
<p>To create a service, you must create a subclass of {@link android.app.Service} or use one
of its existing subclasses. In your implementation, you must override some callback methods that
handle key aspects of the service lifecycle and provide a mechanism that allows the components to
bind to the service, if appropriate. These are the most important callback methods that you should
override:</p>
<dl>
<dt>{@link android.app.Service#onStartCommand onStartCommand()}</dt>
<dd>The system calls this method when another component, such as an activity,
requests that the service be started, by calling {@link android.content.Context#startService
startService()}. Once this method executes, the service is started and can run in the
<dd>The system invokes this method by calling {@link android.content.Context#startService
startService()} when another component (such as an activity) requests that the service be started.
When this method executes, the service is started and can run in the
background indefinitely. If you implement this, it is your responsibility to stop the service when
its work is done, by calling {@link android.app.Service#stopSelf stopSelf()} or {@link
android.content.Context#stopService stopService()}. (If you only want to provide binding, you don't
need to implement this method.)</dd>
its work is complete by calling {@link android.app.Service#stopSelf stopSelf()} or {@link
android.content.Context#stopService stopService()}. If you only want to provide binding, you don't
need to implement this method.</dd>
<dt>{@link android.app.Service#onBind onBind()}</dt>
<dd>The system calls this method when another component wants to bind with the
service (such as to perform RPC), by calling {@link android.content.Context#bindService
bindService()}. In your implementation of this method, you must provide an interface that clients
use to communicate with the service, by returning an {@link android.os.IBinder}. You must always
implement this method, but if you don't want to allow binding, then you should return null.</dd>
<dd>The system invokes this method by calling {@link android.content.Context#bindService
bindService()} when another component wants to bind with the service (such as to perform RPC).
In your implementation of this method, you must provide an interface that clients
use to communicate with the service by returning an {@link android.os.IBinder}. You must always
implement this method; however, if you don't want to allow binding, you should return
null.</dd>
<dt>{@link android.app.Service#onCreate()}</dt>
<dd>The system calls this method when the service is first created, to perform one-time setup
procedures (before it calls either {@link android.app.Service#onStartCommand onStartCommand()} or
<dd>The system invokes this method to perform one-time setup procedures when the service is
initially created (before it calls either
{@link android.app.Service#onStartCommand onStartCommand()} or
{@link android.app.Service#onBind onBind()}). If the service is already running, this method is not
called.</dd>
<dt>{@link android.app.Service#onDestroy()}</dt>
<dd>The system calls this method when the service is no longer used and is being destroyed.
<dd>The system invokes this method when the service is no longer used and is being destroyed.
Your service should implement this to clean up any resources such as threads, registered
listeners, receivers, etc. This is the last call the service receives.</dd>
listeners, or receivers. This is the last call that the service receives.</dd>
</dl>
<p>If a component starts the service by calling {@link
android.content.Context#startService startService()} (which results in a call to {@link
android.app.Service#onStartCommand onStartCommand()}), then the service
remains running until it stops itself with {@link android.app.Service#stopSelf()} or another
android.app.Service#onStartCommand onStartCommand()}), the service
continues to run until it stops itself with {@link android.app.Service#stopSelf()} or another
component stops it by calling {@link android.content.Context#stopService stopService()}.</p>
<p>If a component calls
{@link android.content.Context#bindService bindService()} to create the service (and {@link
android.app.Service#onStartCommand onStartCommand()} is <em>not</em> called), then the service runs
only as long as the component is bound to it. Once the service is unbound from all clients, the
system destroys it.</p>
{@link android.content.Context#bindService bindService()} to create the service and {@link
android.app.Service#onStartCommand onStartCommand()} is <em>not</em> called, the service runs
only as long as the component is bound to it. After the service is unbound from all of its clients,
the system destroys it.</p>
<p>The Android system will force-stop a service only when memory is low and it must recover system
<p>The Android system force-stops a service only when memory is low and it must recover system
resources for the activity that has user focus. If the service is bound to an activity that has user
focus, then it's less likely to be killed, and if the service is declared to <a
href="#Foreground">run in the foreground</a> (discussed later), then it will almost never be killed.
Otherwise, if the service was started and is long-running, then the system will lower its position
in the list of background tasks over time and the service will become highly susceptible to
killing&mdash;if your service is started, then you must design it to gracefully handle restarts
focus, it's less likely to be killed; if the service is declared to <a
href="#Foreground">run in the foreground</a>, it's rarely killed.
If the service is started and is long-running, the system lowers its position
in the list of background tasks over time, and the service becomes highly susceptible to
killing&mdash;if your service is started, you must design it to gracefully handle restarts
by the system. If the system kills your service, it restarts it as soon as resources become
available again (though this also depends on the value you return from {@link
android.app.Service#onStartCommand onStartCommand()}, as discussed later). For more information
available, but this also depends on the value that you return from {@link
android.app.Service#onStartCommand onStartCommand()}. For more information
about when the system might destroy a service, see the <a
href="{@docRoot}guide/components/processes-and-threads.html">Processes and Threading</a>
document.</p>
<p>In the following sections, you'll see how you can create each type of service and how to use
it from other application components.</p>
<p>In the following sections, you'll see how you can create the
{@link android.content.Context#startService startService()} and
{@link android.content.Context#bindService bindService()} service methods, as well as how to use
them from other application components.</p>
<h3 id="Declaring">Declaring a service in the manifest</h3>
<p>Like activities (and other components), you must declare all services in your application's
manifest file.</p>
<p>You must declare all services in your application's
manifest file, just as you do for activities and other components.</p>
<p>To declare your service, add a <a
href="{@docRoot}guide/topics/manifest/service-element.html">{@code <service>}</a> element
href="{@docRoot}guide/topics/manifest/service-element.html">{@code &lt;service&gt;}</a> element
as a child of the <a
href="{@docRoot}guide/topics/manifest/application-element.html">{@code <application>}</a>
element. For example:</p>
href="{@docRoot}guide/topics/manifest/application-element.html">{@code &lt;application&gt;}</a>
element. Here is an example:</p>
<pre>
&lt;manifest ... &gt;
@@ -205,48 +218,44 @@ element. For example:</p>
</pre>
<p>See the <a
href="{@docRoot}guide/topics/manifest/service-element.html">{@code <service>}</a> element
href="{@docRoot}guide/topics/manifest/service-element.html">{@code &lt;service&gt;}</a> element
reference for more information about declaring your service in the manifest.</p>
<p>There are other attributes you can include in the <a
href="{@docRoot}guide/topics/manifest/service-element.html">{@code <service>}</a> element to
define properties such as permissions required to start the service and the process in
<p>There are other attributes that you can include in the <a
href="{@docRoot}guide/topics/manifest/service-element.html">{@code &lt;service&gt;}</a> element to
define properties such as the permissions that are required to start the service and the process in
which the service should run. The <a
href="{@docRoot}guide/topics/manifest/service-element.html#nm">{@code android:name}</a>
attribute is the only required attribute&mdash;it specifies the class name of the service. Once
you publish your application, you should not change this name, because if you do, you risk breaking
attribute is the only required attribute&mdash;it specifies the class name of the service. After
you publish your application, leave this name unchanged to avoid the risk of breaking
code due to dependence on explicit intents to start or bind the service (read the blog post, <a
href="http://android-developers.blogspot.com/2011/06/things-that-cannot-change.html">Things
That Cannot Change</a>).
<p>To ensure your app is secure, <strong>always use an explicit intent when starting or binding
your {@link android.app.Service}</strong> and do not declare intent filters for the service. If
it's critical that you allow for some amount of ambiguity as to which service starts, you can
supply intent filters for your services and exclude the component name from the {@link
android.content.Intent}, but you then must set the package for the intent with {@link
android.content.Intent#setPackage setPackage()}, which provides sufficient disambiguation for the
target service.</p>
<p class="caution"><strong>Caution</strong>: To ensure that your app is secure, always use an
explicit intent when starting a {@link android.app.Service} and do not declare intent filters for
your services. Using an implicit intent to start a service is a security hazard because you cannot
be certain of the service that will respond to the intent, and the user cannot see which service
starts. Beginning with Android 5.0 (API level 21), the system throws an exception if you call
{@link android.content.Context#bindService bindService()} with an implicit intent.</p>
<p>Additionally, you can ensure that your service is available to only your app by
<p>You can ensure that your service is available to only your app by
including the <a
href="{@docRoot}guide/topics/manifest/service-element.html#exported">{@code android:exported}</a>
attribute and setting it to {@code "false"}. This effectively stops other apps from starting your
attribute and setting it to {@code false}. This effectively stops other apps from starting your
service, even when using an explicit intent.</p>
<h2 id="CreatingStartedService">Creating a Started Service</h2>
<h2 id="CreatingStartedService">Creating a started service</h2>
<p>A started service is one that another component starts by calling {@link
android.content.Context#startService startService()}, resulting in a call to the service's
android.content.Context#startService startService()}, which results in a call to the service's
{@link android.app.Service#onStartCommand onStartCommand()} method.</p>
<p>When a service is started, it has a lifecycle that's independent of the
component that started it and the service can run in the background indefinitely, even if
component that started it. The service can run in the background indefinitely, even if
the component that started it is destroyed. As such, the service should stop itself when its job
is done by calling {@link android.app.Service#stopSelf stopSelf()}, or another component can stop it
by calling {@link android.content.Context#stopService stopService()}.</p>
is complete by calling {@link android.app.Service#stopSelf stopSelf()}, or another component can
stop it by calling {@link android.content.Context#stopService stopService()}.</p>
<p>An application component such as an activity can start the service by calling {@link
android.content.Context#startService startService()} and passing an {@link android.content.Intent}
@@ -254,65 +263,65 @@ that specifies the service and includes any data for the service to use. The ser
this {@link android.content.Intent} in the {@link android.app.Service#onStartCommand
onStartCommand()} method.</p>
<p>For instance, suppose an activity needs to save some data to an online database. The activity can
start a companion service and deliver it the data to save by passing an intent to {@link
<p>For instance, suppose an activity needs to save some data to an online database. The activity
can start a companion service and deliver it the data to save by passing an intent to {@link
android.content.Context#startService startService()}. The service receives the intent in {@link
android.app.Service#onStartCommand onStartCommand()}, connects to the Internet and performs the
database transaction. When the transaction is done, the service stops itself and it is
android.app.Service#onStartCommand onStartCommand()}, connects to the Internet, and performs the
database transaction. When the transaction is complete, the service stops itself and is
destroyed.</p>
<p class="caution"><strong>Caution:</strong> A service runs in the same process as the application
in which it is declared and in the main thread of that application, by default. So, if your service
in which it is declared and in the main thread of that application by default. If your service
performs intensive or blocking operations while the user interacts with an activity from the same
application, the service will slow down activity performance. To avoid impacting application
performance, you should start a new thread inside the service.</p>
application, the service slows down activity performance. To avoid impacting application
performance, start a new thread inside the service.</p>
<p>Traditionally, there are two classes you can extend to create a started service:</p>
<dl>
<dt>{@link android.app.Service}</dt>
<dd>This is the base class for all services. When you extend this class, it's important that
you create a new thread in which to do all the service's work, because the service uses your
application's main thread, by default, which could slow the performance of any activity your
<dd>This is the base class for all services. When you extend this class, it's important to
create a new thread in which the service can complete all of its work; the service uses your
application's main thread by default, which can slow the performance of any activity that your
application is running.</dd>
<dt>{@link android.app.IntentService}</dt>
<dd>This is a subclass of {@link android.app.Service} that uses a worker thread to handle all
start requests, one at a time. This is the best option if you don't require that your service
handle multiple requests simultaneously. All you need to do is implement {@link
<dd>This is a subclass of {@link android.app.Service} that uses a worker thread to handle all of
the start requests, one at a time. This is the best option if you don't require that your service
handle multiple requests simultaneously. Implement {@link
android.app.IntentService#onHandleIntent onHandleIntent()}, which receives the intent for each
start request so you can do the background work.</dd>
start request so that you can complete the background work.</dd>
</dl>
<p>The following sections describe how you can implement your service using either one for these
classes.</p>
<h3 id="ExtendingIntentService">Extending the IntentService class</h3>
<p>Because most started services don't need to handle multiple requests simultaneously
(which can actually be a dangerous multi-threading scenario), it's probably best if you
<p>Because most of the started services don't need to handle multiple requests simultaneously
(which can actually be a dangerous multi-threading scenario), it's best that you
implement your service using the {@link android.app.IntentService} class.</p>
<p>The {@link android.app.IntentService} does the following:</p>
<p>The {@link android.app.IntentService} class does the following:</p>
<ul>
<li>Creates a default worker thread that executes all intents delivered to {@link
android.app.Service#onStartCommand onStartCommand()} separate from your application's main
<li>It creates a default worker thread that executes all of the intents that are delivered to
{@link android.app.Service#onStartCommand onStartCommand()}, separate from your application's main
thread.</li>
<li>Creates a work queue that passes one intent at a time to your {@link
android.app.IntentService#onHandleIntent onHandleIntent()} implementation, so you never have to
worry about multi-threading.</li>
<li>Stops the service after all start requests have been handled, so you never have to call
<li>Stops the service after all of the start requests are handled, so you never have to call
{@link android.app.Service#stopSelf}.</li>
<li>Provides default implementation of {@link android.app.IntentService#onBind onBind()} that
returns null.</li>
<li>Provides a default implementation of {@link android.app.IntentService#onBind onBind()}
that returns null.</li>
<li>Provides a default implementation of {@link android.app.IntentService#onStartCommand
onStartCommand()} that sends the intent to the work queue and then to your {@link
android.app.IntentService#onHandleIntent onHandleIntent()} implementation.</li>
</ul>
<p>All this adds up to the fact that all you need to do is implement {@link
android.app.IntentService#onHandleIntent onHandleIntent()} to do the work provided by the
client. (Though, you also need to provide a small constructor for the service.)</p>
<p>To complete the work that is provided by the client, implement {@link
android.app.IntentService#onHandleIntent onHandleIntent()}.
However, you also need to provide a small constructor for the service.</p>
<p>Here's an example implementation of {@link android.app.IntentService}:</p>
@@ -352,12 +361,12 @@ android.app.IntentService#onHandleIntent onHandleIntent()}.</p>
<p>If you decide to also override other callback methods, such as {@link
android.app.IntentService#onCreate onCreate()}, {@link
android.app.IntentService#onStartCommand onStartCommand()}, or {@link
android.app.IntentService#onDestroy onDestroy()}, be sure to call the super implementation, so
android.app.IntentService#onDestroy onDestroy()}, be sure to call the super implementation so
that the {@link android.app.IntentService} can properly handle the life of the worker thread.</p>
<p>For example, {@link android.app.IntentService#onStartCommand onStartCommand()} must return
the default implementation (which is how the intent gets delivered to {@link
android.app.IntentService#onHandleIntent onHandleIntent()}):</p>
the default implementation, which is how the intent is delivered to {@link
android.app.IntentService#onHandleIntent onHandleIntent()}:</p>
<pre>
&#64;Override
@@ -369,22 +378,21 @@ public int onStartCommand(Intent intent, int flags, int startId) {
<p>Besides {@link android.app.IntentService#onHandleIntent onHandleIntent()}, the only method
from which you don't need to call the super class is {@link android.app.IntentService#onBind
onBind()} (but you only need to implement that if your service allows binding).</p>
onBind()}. You need to implement this only if your service allows binding.</p>
<p>In the next section, you'll see how the same kind of service is implemented when extending
the base {@link android.app.Service} class, which is a lot more code, but which might be
the base {@link android.app.Service} class, which uses more code, but might be
appropriate if you need to handle simultaneous start requests.</p>
<h3 id="ExtendingService">Extending the Service class</h3>
<p>As you saw in the previous section, using {@link android.app.IntentService} makes your
<p>Using {@link android.app.IntentService} makes your
implementation of a started service very simple. If, however, you require your service to
perform multi-threading (instead of processing start requests through a work queue), then you
perform multi-threading (instead of processing start requests through a work queue), you
can extend the {@link android.app.Service} class to handle each intent.</p>
<p>For comparison, the following example code is an implementation of the {@link
android.app.Service} class that performs the exact same work as the example above using {@link
<p>For comparison, the following example code shows an implementation of the {@link
android.app.Service} class that performs the same work as the previous example using {@link
android.app.IntentService}. That is, for each start request, it uses a worker thread to perform the
job and processes only one request at a time.</p>
@@ -460,20 +468,20 @@ public class HelloService extends Service {
<p>However, because you handle each call to {@link android.app.Service#onStartCommand
onStartCommand()} yourself, you can perform multiple requests simultaneously. That's not what
this example does, but if that's what you want, then you can create a new thread for each
request and run them right away (instead of waiting for the previous request to finish).</p>
this example does, but if that's what you want, you can create a new thread for each
request and run them right away instead of waiting for the previous request to finish.</p>
<p>Notice that the {@link android.app.Service#onStartCommand onStartCommand()} method must return an
integer. The integer is a value that describes how the system should continue the service in the
event that the system kills it (as discussed above, the default implementation for {@link
android.app.IntentService} handles this for you, though you are able to modify it). The return value
event that the system kills it. The default implementation for {@link
android.app.IntentService} handles this for you, but you are able to modify it. The return value
from {@link android.app.Service#onStartCommand onStartCommand()} must be one of the following
constants:</p>
<dl>
<dt>{@link android.app.Service#START_NOT_STICKY}</dt>
<dd>If the system kills the service after {@link android.app.Service#onStartCommand
onStartCommand()} returns, <em>do not</em> recreate the service, unless there are pending
onStartCommand()} returns, <em>do not</em> recreate the service unless there are pending
intents to deliver. This is the safest option to avoid running your service when not necessary
and when your application can simply restart any unfinished jobs.</dd>
<dt>{@link android.app.Service#START_STICKY}</dt>
@@ -481,9 +489,9 @@ and when your application can simply restart any unfinished jobs.</dd>
onStartCommand()} returns, recreate the service and call {@link
android.app.Service#onStartCommand onStartCommand()}, but <em>do not</em> redeliver the last intent.
Instead, the system calls {@link android.app.Service#onStartCommand onStartCommand()} with a
null intent, unless there were pending intents to start the service, in which case,
null intent unless there are pending intents to start the service. In that case,
those intents are delivered. This is suitable for media players (or similar services) that are not
executing commands, but running indefinitely and waiting for a job.</dd>
executing commands but are running indefinitely and waiting for a job.</dd>
<dt>{@link android.app.Service#START_REDELIVER_INTENT}</dt>
<dd>If the system kills the service after {@link android.app.Service#onStartCommand
onStartCommand()} returns, recreate the service and call {@link
@@ -494,35 +502,35 @@ actively performing a job that should be immediately resumed, such as downloadin
<p>For more details about these return values, see the linked reference documentation for each
constant.</p>
<h3 id="StartingAService">Starting a Service</h3>
<h3 id="StartingAService">Starting a service</h3>
<p>You can start a service from an activity or other application component by passing an
{@link android.content.Intent} (specifying the service to start) to {@link
android.content.Context#startService startService()}. The Android system calls the service's {@link
android.app.Service#onStartCommand onStartCommand()} method and passes it the {@link
android.content.Intent}. (You should never call {@link android.app.Service#onStartCommand
onStartCommand()} directly.)</p>
android.content.Intent}.
<p class="note"><strong>Note</strong>: Never call
{@link android.app.Service#onStartCommand onStartCommand()} directly.</p>
<p>For example, an activity can start the example service in the previous section ({@code
HelloService}) using an explicit intent with {@link android.content.Context#startService
startService()}:</p>
startService()}, as shown here:</p>
<pre>
Intent intent = new Intent(this, HelloService.class);
startService(intent);
</pre>
<p>The {@link android.content.Context#startService startService()} method returns immediately and
<p>The {@link android.content.Context#startService startService()} method returns immediately, and
the Android system calls the service's {@link android.app.Service#onStartCommand
onStartCommand()} method. If the service is not already running, the system first calls {@link
android.app.Service#onCreate onCreate()}, then calls {@link android.app.Service#onStartCommand
onStartCommand()}.</p>
android.app.Service#onCreate onCreate()}, and then it calls
{@link android.app.Service#onStartCommand onStartCommand()}.</p>
<p>If the service does not also provide binding, the intent delivered with {@link
<p>If the service does not also provide binding, the intent that is delivered with {@link
android.content.Context#startService startService()} is the only mode of communication between the
application component and the service. However, if you want the service to send a result back, then
application component and the service. However, if you want the service to send a result back,
the client that starts the service can create a {@link android.app.PendingIntent} for a broadcast
(with {@link android.app.PendingIntent#getBroadcast getBroadcast()}) and deliver it to the service
in the {@link android.content.Intent} that starts the service. The service can then use the
@@ -533,109 +541,102 @@ broadcast to deliver a result.</p>
the service (with {@link android.app.Service#stopSelf stopSelf()} or {@link
android.content.Context#stopService stopService()}) is required to stop it.</p>
<h3 id="Stopping">Stopping a service</h3>
<p>A started service must manage its own lifecycle. That is, the system does not stop or
destroy the service unless it must recover system memory and the service
continues to run after {@link android.app.Service#onStartCommand onStartCommand()} returns. So,
the service must stop itself by calling {@link android.app.Service#stopSelf stopSelf()} or another
continues to run after {@link android.app.Service#onStartCommand onStartCommand()} returns. The
service must stop itself by calling {@link android.app.Service#stopSelf stopSelf()}, or another
component can stop it by calling {@link android.content.Context#stopService stopService()}.</p>
<p>Once requested to stop with {@link android.app.Service#stopSelf stopSelf()} or {@link
android.content.Context#stopService stopService()}, the system destroys the service as soon as
possible.</p>
<p>However, if your service handles multiple requests to {@link
android.app.Service#onStartCommand onStartCommand()} concurrently, then you shouldn't stop the
service when you're done processing a start request, because you might have since received a new
<p>If your service handles multiple requests to {@link
android.app.Service#onStartCommand onStartCommand()} concurrently, you shouldn't stop the
service when you're done processing a start request, as you might have received a new
start request (stopping at the end of the first request would terminate the second one). To avoid
this problem, you can use {@link android.app.Service#stopSelf(int)} to ensure that your request to
stop the service is always based on the most recent start request. That is, when you call {@link
android.app.Service#stopSelf(int)}, you pass the ID of the start request (the <code>startId</code>
delivered to {@link android.app.Service#onStartCommand onStartCommand()}) to which your stop request
corresponds. Then if the service received a new start request before you were able to call {@link
android.app.Service#stopSelf(int)}, then the ID will not match and the service will not stop.</p>
corresponds. Then, if the service receives a new start request before you are able to call {@link
android.app.Service#stopSelf(int)}, the ID does not match and the service does not stop.</p>
<p class="caution"><strong>Caution:</strong> It's important that your application stops its services
when it's done working, to avoid wasting system resources and consuming battery power. If necessary,
other components can stop the service by calling {@link
<p class="caution"><strong>Caution:</strong> To avoid wasting system resources and consuming
battery power, ensure that your application stops its services when it's done working.
If necessary, other components can stop the service by calling {@link
android.content.Context#stopService stopService()}. Even if you enable binding for the service,
you must always stop the service yourself if it ever received a call to {@link
you must always stop the service yourself if it ever receives a call to {@link
android.app.Service#onStartCommand onStartCommand()}.</p>
<p>For more information about the lifecycle of a service, see the section below about <a
href="#Lifecycle">Managing the Lifecycle of a Service</a>.</p>
<h2 id="CreatingBoundService">Creating a Bound Service</h2>
<h2 id="CreatingBoundService">Creating a bound service</h2>
<p>A bound service is one that allows application components to bind to it by calling {@link
android.content.Context#bindService bindService()} in order to create a long-standing connection
(and generally does not allow components to <em>start</em> it by calling {@link
android.content.Context#startService startService()}).</p>
android.content.Context#bindService bindService()} to create a long-standing connection.
It generally doesn't allow components to <em>start</em> it by calling {@link
android.content.Context#startService startService()}.</p>
<p>You should create a bound service when you want to interact with the service from activities
<p>Create a bound service when you want to interact with the service from activities
and other components in your application or to expose some of your application's functionality to
other applications, through interprocess communication (IPC).</p>
other applications through interprocess communication (IPC).</p>
<p>To create a bound service, you must implement the {@link
<p>To create a bound service, implement the {@link
android.app.Service#onBind onBind()} callback method to return an {@link android.os.IBinder} that
defines the interface for communication with the service. Other application components can then call
{@link android.content.Context#bindService bindService()} to retrieve the interface and
begin calling methods on the service. The service lives only to serve the application component that
is bound to it, so when there are no components bound to the service, the system destroys it
(you do <em>not</em> need to stop a bound service in the way you must when the service is started
through {@link android.app.Service#onStartCommand onStartCommand()}).</p>
is bound to it, so when there are no components bound to the service, the system destroys it.
You do <em>not</em> need to stop a bound service in the same way that you must when the service is
started through {@link android.app.Service#onStartCommand onStartCommand()}.</p>
<p>To create a bound service, the first thing you must do is define the interface that specifies
how a client can communicate with the service. This interface between the service
<p>To create a bound service, you must define the interface that specifies how a client can
communicate with the service. This interface between the service
and a client must be an implementation of {@link android.os.IBinder} and is what your service must
return from the {@link android.app.Service#onBind
onBind()} callback method. Once the client receives the {@link android.os.IBinder}, it can begin
onBind()} callback method. After the client receives the {@link android.os.IBinder}, it can begin
interacting with the service through that interface.</p>
<p>Multiple clients can bind to the service at once. When a client is done interacting with the
service, it calls {@link android.content.Context#unbindService unbindService()} to unbind. Once
there are no clients bound to the service, the system destroys the service.</p>
<p>Multiple clients can bind to the service simultaneously. When a client is done interacting with
the service, it calls {@link android.content.Context#unbindService unbindService()} to unbind.
When there are no clients bound to the service, the system destroys the service.</p>
<p>There are multiple ways to implement a bound service and the implementation is more
complicated than a started service, so the bound service discussion appears in a separate
document about <a
<p>There are multiple ways to implement a bound service, and the implementation is more
complicated than a started service. For these reasons, the bound service discussion appears in a
separate document about <a
href="{@docRoot}guide/components/bound-services.html">Bound Services</a>.</p>
<h2 id="Notifications">Sending notifications to the user</h2>
<h2 id="Notifications">Sending Notifications to the User</h2>
<p>Once running, a service can notify the user of events using <a
<p>When a service is running, it can notify the user of events using <a
href="{@docRoot}guide/topics/ui/notifiers/toasts.html">Toast Notifications</a> or <a
href="{@docRoot}guide/topics/ui/notifiers/notifications.html">Status Bar Notifications</a>.</p>
<p>A toast notification is a message that appears on the surface of the current window for a
moment then disappears, while a status bar notification provides an icon in the status bar with a
<p>A toast notification is a message that appears on the surface of the current window for only a
moment before disappearing. A status bar notification provides an icon in the status bar with a
message, which the user can select in order to take an action (such as start an activity).</p>
<p>Usually, a status bar notification is the best technique when some background work has completed
(such as a file completed
downloading) and the user can now act on it. When the user selects the notification from the
expanded view, the notification can start an activity (such as to view the downloaded file).</p>
<p>Usually, a status bar notification is the best technique to use when background work such as
a file download has completed, and the user can now act on it. When the user
selects the notification from the expanded view, the notification can start an activity
(such as to display the downloaded file).</p>
<p>See the <a
href="{@docRoot}guide/topics/ui/notifiers/toasts.html">Toast Notifications</a> or <a
href="{@docRoot}guide/topics/ui/notifiers/notifications.html">Status Bar Notifications</a>
developer guides for more information.</p>
<h2 id="Foreground">Running a service in the foreground</h2>
<h2 id="Foreground">Running a Service in the Foreground</h2>
<p>A foreground service is a service that's considered to be something the
user is actively aware of and thus not a candidate for the system to kill when low on memory. A
<p>A foreground service is a service that the
user is actively aware of and is not a candidate for the system to kill when low on memory. A
foreground service must provide a notification for the status bar, which is placed under the
"Ongoing" heading, which means that the notification cannot be dismissed unless the service is
either stopped or removed from the foreground.</p>
<em>Ongoing</em> heading. This means that the notification cannot be dismissed unless the service
is either stopped or removed from the foreground.</p>
<p>For example, a music player that plays music from a service should be set to run in the
foreground, because the user is explicitly aware
@@ -643,9 +644,9 @@ of its operation. The notification in the status bar might indicate the current
the user to launch an activity to interact with the music player.</p>
<p>To request that your service run in the foreground, call {@link
android.app.Service#startForeground startForeground()}. This method takes two parameters: an integer
that uniquely identifies the notification and the {@link
android.app.Notification} for the status bar. For example:</p>
android.app.Service#startForeground startForeground()}. This method takes two parameters: an
integer that uniquely identifies the notification and the {@link
android.app.Notification} for the status bar. Here is an example:</p>
<pre>
Notification notification = new Notification(R.drawable.icon, getText(R.string.ticker_text),
@@ -657,30 +658,27 @@ notification.setLatestEventInfo(this, getText(R.string.notification_title),
startForeground(ONGOING_NOTIFICATION_ID, notification);
</pre>
<p class="caution"><strong>Caution:</strong> The integer ID you give to {@link
<p class="caution"><strong>Caution:</strong> The integer ID that you give to {@link
android.app.Service#startForeground startForeground()} must not be 0.</p>
<p>To remove the service from the foreground, call {@link
android.app.Service#stopForeground stopForeground()}. This method takes a boolean, indicating
android.app.Service#stopForeground stopForeground()}. This method takes a boolean, which indicates
whether to remove the status bar notification as well. This method does <em>not</em> stop the
service. However, if you stop the service while it's still running in the foreground, then the
service. However, if you stop the service while it's still running in the foreground, the
notification is also removed.</p>
<p>For more information about notifications, see <a
href="{@docRoot}guide/topics/ui/notifiers/notifications.html">Creating Status Bar
Notifications</a>.</p>
<h2 id="Lifecycle">Managing the lifecycle of a service</h2>
<p>The lifecycle of a service is much simpler than that of an activity. However, it's even more
important that you pay close attention to how your service is created and destroyed because a
service can run in the background without the user being aware.</p>
<h2 id="Lifecycle">Managing the Lifecycle of a Service</h2>
<p>The lifecycle of a service is much simpler than that of an activity. However, it's even more important
that you pay close attention to how your service is created and destroyed, because a service
can run in the background without the user being aware.</p>
<p>The service lifecycle&mdash;from when it's created to when it's destroyed&mdash;can follow two
different paths:</p>
<p>The service lifecycle&mdash;from when it's created to when it's destroyed&mdash;can follow
either of these two paths:</p>
<ul>
<li>A started service
@@ -689,27 +687,26 @@ android.content.Context#startService startService()}. The service then runs inde
stop itself by calling {@link
android.app.Service#stopSelf() stopSelf()}. Another component can also stop the
service by calling {@link android.content.Context#stopService
stopService()}. When the service is stopped, the system destroys it..</p></li>
stopService()}. When the service is stopped, the system destroys it.</p></li>
<li>A bound service
<p>The service is created when another component (a client) calls {@link
android.content.Context#bindService bindService()}. The client then communicates with the service
through an {@link android.os.IBinder} interface. The client can close the connection by calling
{@link android.content.Context#unbindService unbindService()}. Multiple clients can bind to
the same service and when all of them unbind, the system destroys the service. (The service
does <em>not</em> need to stop itself.)</p></li>
the same service and when all of them unbind, the system destroys the service. The service
does <em>not</em> need to stop itself.</p></li>
</ul>
<p>These two paths are not entirely separate. That is, you can bind to a service that was already
started with {@link android.content.Context#startService startService()}. For example, a background
music service could be started by calling {@link android.content.Context#startService
<p>These two paths are not entirely separate. You can bind to a service that is already
started with {@link android.content.Context#startService startService()}. For example, you can
start a background music service by calling {@link android.content.Context#startService
startService()} with an {@link android.content.Intent} that identifies the music to play. Later,
possibly when the user wants to exercise some control over the player or get information about the
current song, an activity can bind to the service by calling {@link
android.content.Context#bindService bindService()}. In cases like this, {@link
android.content.Context#bindService bindService()}. In cases such as this, {@link
android.content.Context#stopService stopService()} or {@link android.app.Service#stopSelf
stopSelf()} does not actually stop the service until all clients unbind. </p>
stopSelf()} doesn't actually stop the service until all of the clients unbind.</p>
<h3 id="LifecycleCallbacks">Implementing the lifecycle callbacks</h3>
@@ -763,20 +760,30 @@ shows the lifecycle when the service is created with {@link android.content.Cont
startService()} and the diagram on the right shows the lifecycle when the service is created
with {@link android.content.Context#bindService bindService()}.</p>
<p>By implementing these methods, you can monitor two nested loops of the service's lifecycle: </p>
<p>Figure 2 illustrates the typical callback methods for a service. Although the figure separates
services that are created by {@link android.content.Context#startService startService()} from those
created by {@link android.content.Context#bindService bindService()}, keep
in mind that any service, no matter how it's started, can potentially allow clients to bind to it.
A service that was initially started with {@link android.app.Service#onStartCommand
onStartCommand()} (by a client calling {@link android.content.Context#startService startService()})
can still receive a call to {@link android.app.Service#onBind onBind()} (when a client calls
{@link android.content.Context#bindService bindService()}).</p>
<p>By implementing these methods, you can monitor these two nested loops of the service's
lifecycle:</p>
<ul>
<li>The <strong>entire lifetime</strong> of a service happens between the time {@link
android.app.Service#onCreate onCreate()} is called and the time {@link
<li>The <strong>entire lifetime</strong> of a service occurs between the time that {@link
android.app.Service#onCreate onCreate()} is called and the time that {@link
android.app.Service#onDestroy} returns. Like an activity, a service does its initial setup in
{@link android.app.Service#onCreate onCreate()} and releases all remaining resources in {@link
android.app.Service#onDestroy onDestroy()}. For example, a
music playback service could create the thread where the music will be played in {@link
android.app.Service#onCreate onCreate()}, then stop the thread in {@link
android.app.Service#onDestroy onDestroy()}. For example, a
music playback service can create the thread where the music is played in {@link
android.app.Service#onCreate onCreate()}, and then it can stop the thread in {@link
android.app.Service#onDestroy onDestroy()}.
<p>The {@link android.app.Service#onCreate onCreate()} and {@link android.app.Service#onDestroy
onDestroy()} methods are called for all services, whether
<p class="note"><strong>Note</strong>: The {@link android.app.Service#onCreate onCreate()}
and {@link android.app.Service#onDestroy onDestroy()} methods are called for all services, whether
they're created by {@link android.content.Context#startService startService()} or {@link
android.content.Context#bindService bindService()}.</p></li>
@@ -784,8 +791,8 @@ android.content.Context#bindService bindService()}.</p></li>
android.app.Service#onStartCommand onStartCommand()} or {@link android.app.Service#onBind onBind()}.
Each method is handed the {@link
android.content.Intent} that was passed to either {@link android.content.Context#startService
startService()} or {@link android.content.Context#bindService bindService()}, respectively.
<p>If the service is started, the active lifetime ends the same time that the entire lifetime
startService()} or {@link android.content.Context#bindService bindService()}.
<p>If the service is started, the active lifetime ends at the same time that the entire lifetime
ends (the service is still active even after {@link android.app.Service#onStartCommand
onStartCommand()} returns). If the service is bound, the active lifetime ends when {@link
android.app.Service#onUnbind onUnbind()} returns.</p>
@@ -795,26 +802,16 @@ android.app.Service#onUnbind onUnbind()} returns.</p>
<p class="note"><strong>Note:</strong> Although a started service is stopped by a call to
either {@link android.app.Service#stopSelf stopSelf()} or {@link
android.content.Context#stopService stopService()}, there is not a respective callback for the
service (there's no {@code onStop()} callback). So, unless the service is bound to a client,
service (there's no {@code onStop()} callback). Unless the service is bound to a client,
the system destroys it when the service is stopped&mdash;{@link
android.app.Service#onDestroy onDestroy()} is the only callback received.</p>
<p>Figure 2 illustrates the typical callback methods for a service. Although the figure separates
services that are created by {@link android.content.Context#startService startService()} from those
created by {@link android.content.Context#bindService bindService()}, keep
in mind that any service, no matter how it's started, can potentially allow clients to bind to it.
So, a service that was initially started with {@link android.app.Service#onStartCommand
onStartCommand()} (by a client calling {@link android.content.Context#startService startService()})
can still receive a call to {@link android.app.Service#onBind onBind()} (when a client calls
{@link android.content.Context#bindService bindService()}).</p>
<p>For more information about creating a service that provides binding, see the <a
href="{@docRoot}guide/components/bound-services.html">Bound Services</a> document,
which includes more information about the {@link android.app.Service#onRebind onRebind()}
callback method in the section about <a
href="{@docRoot}guide/components/bound-services.html#Lifecycle">Managing the Lifecycle of
a Bound Service</a>.</p>
href="{@docRoot}guide/components/bound-services.html#Lifecycle">Managing the lifecycle of
a bound service</a>.</p>
<!--
<h2>Beginner's Path</h2>

470
docs/html/training/articles/security-tips.jd
View File

@@ -6,34 +6,32 @@ page.article=true
<div id="tb">
<h2>In this document</h2>
<ol class="nolist">
<li><a href="#StoringData">Storing Data</a></li>
<li><a href="#Permissions">Using Permissions</a></li>
<li><a href="#Networking">Using Networking</a></li>
<li><a href="#InputValidation">Performing Input Validation</a></li>
<li><a href="#UserData">Handling User Data</a></li>
<li><a href="#StoringData">Storing data</a></li>
<li><a href="#Permissions">Using permissions</a></li>
<li><a href="#Networking">Using networking</a></li>
<li><a href="#InputValidation">Performing input validation</a></li>
<li><a href="#UserData">Handling user data</a></li>
<li><a href="#WebView">Using WebView</a></li>
<li><a href="#Crypto">Using Cryptography</a></li>
<li><a href="#IPC">Using Interprocess Communication</a></li>
<li><a href="#DynamicCode">Dynamically Loading Code</a></li>
<li><a href="#Dalvik">Security in a Virtual Machine</a></li>
<li><a href="#Native">Security in Native Code</a></li>
<li><a href="#Crypto">Using cryptography</a></li>
<li><a href="#IPC">Using interprocess communication</a></li>
<li><a href="#DynamicCode">Dynamically loading code</a></li>
<li><a href="#Dalvik">Security in a virtual machine</a></li>
<li><a href="#Native">Security in native code</a></li>
</ol>
<h2>See also</h2>
<ul>
<li><a href="http://source.android.com/tech/security/index.html">Android
Security Overview</a></li>
Security Overview</a></li>
<li><a href="{@docRoot}guide/topics/security/permissions.html">Permissions</a></li>
</ul>
</div></div>
<p>Android has security features built
into the operating system that significantly reduce the frequency and impact of
application security issues. The system is designed so you can typically build your apps with
default system and file permissions and avoid difficult decisions about security.</p>
<p>Android has built-in security features that significantly reduce the frequency and impact of
application security issues. The system is designed so that you can typically build your apps with
the default system and file permissions and avoid difficult decisions about security.</p>
<p>Some of the core security features that help you build secure apps
include:
<p>The following core security features help you build secure apps:
<ul>
<li>The Android Application Sandbox, which isolates your app data and code execution
from other apps.</li>
@@ -43,47 +41,54 @@ security functionality such as cryptography, permissions, and secure
<li>Technologies like ASLR, NX, ProPolice, safe_iop, OpenBSD dlmalloc, OpenBSD
calloc, and Linux mmap_min_addr to mitigate risks associated with common memory
management errors.</li>
<li>An encrypted filesystem that can be enabled to protect data on lost or
<li>An encrypted file system that can be enabled to protect data on lost or
stolen devices.</li>
<li>User-granted permissions to restrict access to system features and user data.</li>
<li>Application-defined permissions to control application data on a per-app basis.</li>
</ul>
<p>Nevertheless, it is important that you be familiar with the Android
<p>It is important that you be familiar with the Android
security best practices in this document. Following these practices as general coding habits
will reduce the likelihood of inadvertently introducing security issues that
reduces the likelihood of inadvertently introducing security issues that
adversely affect your users.</p>
<h2 id="StoringData">Storing Data</h2>
<h2 id="StoringData">Storing data</h2>
<p>The most common security concern for an application on Android is whether the data
that you save on the device is accessible to other apps. There are three fundamental
ways to save data on the device:</p>
<ul>
<li>Internal storage.</li>
<li>External storage.</li>
<li>Content providers.</li>
</ul>
The following paragraphs describe the security issues associated with each approach.
<h3 id="InternalStorage">Using internal storage</h3>
<p>By default, files that you create on <a
href="{@docRoot}guide/topics/data/data-storage.html#filesInternal">internal
storage</a> are accessible only to your app. This
protection is implemented by Android and is sufficient for most
applications.</p>
storage</a> are accessible only to your app.
Android implements this protection, and it's sufficient for most applications.</p>
<p>You should generally avoid using the {@link android.content.Context#MODE_WORLD_WRITEABLE} or
<p>Generally, avoid the {@link android.content.Context#MODE_WORLD_WRITEABLE} or
{@link android.content.Context#MODE_WORLD_READABLE} modes for
<acronym title="Interprocess Communication">IPC</acronym> files because they do not provide
the ability to limit data access to particular applications, nor do they
provide any control on data format. If you want to share your data with other
app processes, you might instead consider using a
provide any control of data format. If you want to share your data with other
app processes, instead consider using a
<a href="{@docRoot}guide/topics/providers/content-providers.html">content provider</a>, which
offers read and write permissions to other apps and can make
dynamic permission grants on a case-by-case basis.</p>
<p>To provide additional protection for sensitive data, you might
choose to encrypt local files using a key that is not directly accessible to the
application. For example, a key can be placed in a {@link java.security.KeyStore}
and protected with a user password that is not stored on the device. While this
<p>To provide additional protection for sensitive data, you can
encrypt local files using a key that is not directly accessible to the
application. For example, you can place a key in a {@link java.security.KeyStore}
and protect it with a user password that is not stored on the device. While this
does not protect data from a root compromise that can monitor the user
inputting the password, it can provide protection for a lost device without <a
href="http://source.android.com/tech/encryption/index.html">file system
@@ -94,14 +99,14 @@ encryption</a>.</p>
<p>Files created on <a
href="{@docRoot}guide/topics/data/data-storage.html#filesExternal">external
storage</a>, such as SD Cards, are globally readable and writable. Because
storage</a>, such as SD cards, are globally readable and writable. Because
external storage can be removed by the user and also modified by any
application, you should not store sensitive information using
application, don't store sensitive information using
external storage.</p>
<p>As with data from any untrusted source, you should <a href="#InputValidation">perform input
validation</a> when handling data from external storage.
We strongly recommend that you not store executables or
<p>You should <a href="#InputValidation">Perform input validation</a> when handling
data from external storage as you would with data from any untrusted source.
You should not store executables or
class files on external storage prior to dynamic loading. If your app
does retrieve executable files from external storage, the files should be signed and
cryptographically verified prior to dynamic loading.</p>
@@ -117,22 +122,22 @@ applications with access to your {@link android.content.ContentProvider}, mark t
href="{@docRoot}guide/topics/manifest/provider-element.html#exported">
android:exported=false</a></code> in the application manifest. Otherwise, set the <code><a
href="{@docRoot}guide/topics/manifest/provider-element.html#exported">android:exported</a></code>
attribute {@code "true"} to allow other apps to access the stored data.
attribute to {@code true} to allow other apps to access the stored data.
</p>
<p>When creating a {@link android.content.ContentProvider}
that will be exported for use by other applications, you can specify a single
that is exported for use by other applications, you can specify a single
<a href="{@docRoot}guide/topics/manifest/provider-element.html#prmsn">permission
</a> for reading and writing, or distinct permissions for reading and writing
within the manifest. We recommend that you limit your permissions to those
</a> for reading and writing, or you can specify distinct permissions for reading and writing.
You should limit your permissions to those
required to accomplish the task at hand. Keep in mind that it’s usually
easier to add permissions later to expose new functionality than it is to take
them away and break existing users.</p>
them away and impact existing users.</p>
<p>If you are using a content provider
for sharing data between only your own apps, it is preferable to use the
<a href="{@docRoot}guide/topics/manifest/permission-element.html#plevel">{@code
android:protectionLevel}</a> attribute set to {@code "signature"} protection.
android:protectionLevel}</a> attribute set to {@code signature} protection.
Signature permissions do not require user confirmation,
so they provide a better user experience and more controlled access to the
content provider data when the apps accessing the data are
@@ -148,7 +153,7 @@ android.content.Intent#FLAG_GRANT_WRITE_URI_PERMISSION} flags in the
that activates the component. The scope of these permissions can be further
limited by the <code><a
href="{@docRoot}guide/topics/manifest/grant-uri-permission-element.html">
&lt;grant-uri-permission element&gt;</a></code>.</p>
&lt;grant-uri-permission&gt;</a></code> element.</p>
<p>When accessing a content provider, use parameterized query methods such as
{@link android.content.ContentProvider#query(Uri,String[],String,String[],String) query()},
@@ -158,11 +163,11 @@ potential SQL injection from untrusted sources. Note that using parameterized me
sufficient if the <code>selection</code> argument is built by concatenating user data
prior to submitting it to the method.</p>
<p>Do not have a false sense of security about the write permission. Consider
that the write permission allows SQL statements which make it possible for some
<p>Don't have a false sense of security about the write permission.
The write permission allows SQL statements that make it possible for some
data to be confirmed using creative <code>WHERE</code> clauses and parsing the
results. For example, an attacker might probe for presence of a specific phone
number in a call-log by modifying a row only if that phone number already
results. For example, an attacker might probe for the presence of a specific phone
number in a call log by modifying a row only if that phone number already
exists. If the content provider data has predictable structure, the write
permission may be equivalent to providing both reading and writing.</p>
@@ -172,7 +177,7 @@ permission may be equivalent to providing both reading and writing.</p>
<h2 id="Permissions">Using Permissions</h2>
<h2 id="Permissions">Using permissions</h2>
<p>Because Android sandboxes applications from each other, applications must explicitly
share resources and data. They do this by declaring the permissions they need for additional
@@ -180,25 +185,25 @@ capabilities not provided by the basic sandbox, including access to device featu
the camera.</p>
<h3 id="RequestingPermissions">Requesting Permissions</h3>
<h3 id="RequestingPermissions">Requesting permissions</h3>
<p>We recommend minimizing the number of permissions that your app requests.
Not having access to sensitive permissions reduces the risk of
inadvertently misusing those permissions, can improve user adoption, and makes
<p>You should minimize the number of permissions that your app requests.
Restricting access to sensitive permissions reduces the risk of
inadvertently misusing those permissions, improves user adoption, and makes
your app less vulnerable for attackers. Generally,
if a permission is not required for your app to function, do not request it.</p>
if a permission is not required for your app to function, don't request it.</p>
<p>If it's possible to design your application in a way that does not require
any permissions, that is preferable. For example, rather than requesting access
to device information to create a unique identifier, create a <a
href="{@docRoot}reference/java/util/UUID.html">GUID</a> for your application
(see the section about <a href="#UserData">Handling User Data</a>). Or, rather than
(see the section about <a href="#UserData">Handling user data</a>). Or, rather than
using external storage (which requires permission), store data
on the internal storage.</p>
<p>In addition to requesting permissions, your application can use the <a
href="{@docRoot}guide/topics/manifest/permission-element.html">{@code <permissions>}</a>
to protect IPC that is security sensitive and will be exposed to other
href="{@docRoot}guide/topics/manifest/permission-element.html">{@code &lt;permission&gt;}</a>
element to protect IPC that is security sensitive and is exposed to other
applications, such as a {@link android.content.ContentProvider}.
In general, we recommend using access controls
other than user confirmed permissions where possible because permissions can
@@ -211,13 +216,14 @@ provided by a single developer.</p>
data over IPC that is available only because your app has permission to access
that data. The clients of your app's IPC interface may not have that same
data-access permission. More details on the frequency and potential effects
of this issue appear in <a class="external-link"
href="https://www.usenix.org/legacy/event/sec11/tech/full_papers/Felt.pdf"> this
research paper</a>, published at USENIX.
of this issue appear in the research paper <a
href="https://www.usenix.org/legacy/event/sec11/tech/full_papers/Felt.pdf" class="external-link">
Permission Re-Delegation: Attacks and Defenses
</a>, published at USENIX.
<h3 id="CreatingPermissions">Creating Permissions</h3>
<h3 id="CreatingPermissions">Creating permissions</h3>
<p>Generally, you should strive to define as few permissions as possible while
satisfying your security requirements. Creating a new permission is relatively
@@ -228,18 +234,18 @@ perform access checks using existing permissions.</p>
<p>If you must create a new permission, consider whether you can accomplish
your task with a <a
href="{@docRoot}guide/topics/manifest/permission-element.html#plevel">"signature"
href="{@docRoot}guide/topics/manifest/permission-element.html#plevel">signature
protection level</a>. Signature permissions are transparent
to the user and only allow access by applications signed by the same developer
as application performing the permission check.</p>
to the user and allow access only by applications signed by the same developer
as the application performing the permission check.</p>
<p>If you create a permission with the <a
href="{@docRoot}guide/topics/manifest/permission-element.html#plevel">"dangerous"
href="{@docRoot}guide/topics/manifest/permission-element.html#plevel">dangerous
protection level</a>, there are a number of complexities
that you need to consider:
<ul>
<li>The permission must have a string that concisely expresses to a user the
security decision they will be required to make.</li>
security decision they are required to make.</li>
<li>The permission string must be localized to many different languages.</li>
<li>Users may choose not to install an application because a permission is
confusing or perceived as risky.</li>
@@ -247,28 +253,28 @@ confusing or perceived as risky.</li>
has not been installed.</li>
</ul>
<p>Each of these poses a significant non-technical challenge for you as the developer
<p>Each of these poses a significant nontechnical challenge for you as the developer
while also confusing your users,
which is why we discourage the use of the "dangerous" permission level.</p>
which is why we discourages the use of the <em>dangerous</em> permission level.</p>
<h2 id="Networking">Using Networking</h2>
<h2 id="Networking">Using networking</h2>
<p>Network transactions are inherently risky for security, because it involves transmitting
<p>Network transactions are inherently risky for security, because they involve transmitting
data that is potentially private to the user. People are increasingly aware of the privacy
concerns of a mobile device, especially when the device performs network transactions,
so it's very important that your app implement all best practices toward keeping the user's
data secure at all times.</p>
<h3 id="IPNetworking">Using IP Networking</h3>
<h3 id="IPNetworking">Using IP networking</h3>
<p>Networking on Android is not significantly different from other Linux
environments. The key consideration is making sure that appropriate protocols
are used for sensitive data, such as {@link javax.net.ssl.HttpsURLConnection} for
secure web traffic. We prefer use of HTTPS over HTTP anywhere that HTTPS is
secure web traffic. You should use HTTPS over HTTP anywhere that HTTPS is
supported on the server, because mobile devices frequently connect on networks
that are not secured, such as public Wi-Fi hotspots.</p>
@@ -278,32 +284,32 @@ class. Given the frequency with which Android devices connect to unsecured
wireless networks using Wi-Fi, the use of secure networking is strongly
encouraged for all applications that communicate over the network.</p>
<p>We have seen some applications use <a
href="http://en.wikipedia.org/wiki/Localhost">localhost</a> network ports for
handling sensitive IPC. We discourage this approach since these interfaces are
accessible by other applications on the device. Instead, you should use an Android IPC
mechanism where authentication is possible such as with a {@link android.app.Service}. (Even
worse than using loopback is to bind to INADDR_ANY since then your application
may receive requests from anywhere.)</p>
<p>Some applications use <a
href="http://en.wikipedia.org/wiki/Localhost" class="external-link">localhost</a> network ports for
handling sensitive IPC. You should not use this approach because these interfaces are
accessible by other applications on the device. Instead, use an Android IPC
mechanism where authentication is possible, such as with a {@link android.app.Service}.
Binding to INADDR_ANY is worse than using loopback because then your application
may receive requests from anywhere.</p>
<p>Also, one common issue that warrants repeating is to make sure that you do
not trust data downloaded from HTTP or other insecure protocols. This includes
<p>Make sure that you don't
trust data downloaded from HTTP or other insecure protocols. This includes
validation of input in {@link android.webkit.WebView} and
any responses to intents issued against HTTP.</p>
<h3>Using Telephony Networking</h3>
<h3>Using telephony networking</h3>
<p>The <acronym title="Short Message Service">SMS</acronym> protocol was primarily designed for
user-to-user communication and is not well-suited for apps that want to transfer data.
Due to the limitations of SMS, we strongly recommend the use of <a
Due to the limitations of SMS, you should use <a
href="{@docRoot}google/gcm/index.html">Google Cloud Messaging</a> (GCM)
and IP networking for sending data messages from a web server to your app on a user device.</p>
<p>Beware that SMS is neither encrypted nor strongly
authenticated on either the network or the device. In particular, any SMS receiver
should expect that a malicious user may have sent the SMS to your application&mdash;Do
not rely on unauthenticated SMS data to perform sensitive commands.
authenticated on either the network or the device. In particular, any SMS receiver
should expect that a malicious user may have sent the SMS to your application. Don't
rely on unauthenticated SMS data to perform sensitive commands.
Also, you should be aware that SMS may be subject to spoofing and/or
interception on the network. On the Android-powered device itself, SMS
messages are transmitted as broadcast intents, so they may be read or captured
@@ -314,32 +320,32 @@ permission.</p>
<h2 id="InputValidation">Performing Input Validation</h2>
<h2 id="InputValidation">Performing input validation</h2>
<p>Insufficient input validation is one of the most common security problems
affecting applications, regardless of what platform they run on. Android does
have platform-level countermeasures that reduce the exposure of applications to
input validation issues and you should use those features where possible. Also
note that selection of type-safe languages tends to reduce the likelihood of
affecting applications, regardless of what platform they run on. Android
has platform-level countermeasures that reduce the exposure of applications to
input validation issues, and you should use those features where possible. Also
note that the selection of type-safe languages tends to reduce the likelihood of
input validation issues.</p>
<p>If you are using native code, then any data read from files, received over
<p>If you are using native code, any data read from files, received over
the network, or received from an IPC has the potential to introduce a security
issue. The most common problems are <a
href="http://en.wikipedia.org/wiki/Buffer_overflow">buffer overflows</a>, <a
href="http://en.wikipedia.org/wiki/Double_free#Use_after_free">use after
href="http://en.wikipedia.org/wiki/Buffer_overflow" class="external-link">buffer overflows</a>, <a
href="http://en.wikipedia.org/wiki/Double_free#Use_after_free" class="external-link">use after
free</a>, and <a
href="http://en.wikipedia.org/wiki/Off-by-one_error">off-by-one errors</a>.
href="http://en.wikipedia.org/wiki/Off-by-one_error" class="external-link">off-by-one errors</a>.
Android provides a number of technologies like <acronym
title="Address Space Layout Randomization">ASLR</acronym> and <acronym
title="Data Execution Prevention">DEP</acronym> that reduce the
exploitability of these errors, but they do not solve the underlying problem.
You can prevent these vulneratbilities by careful handling pointers and managing
exploitability of these errors, but they don't solve the underlying problem.
You can prevent these vulnerabilities by carefully handling pointers and managing
buffers.</p>
<p>Dynamic, string based languages such as JavaScript and SQL are also subject
<p>Dynamic, string-based languages such as JavaScript and SQL are also subject
to input validation problems due to escape characters and <a
href="http://en.wikipedia.org/wiki/Code_injection">script injection</a>.</p>
href="http://en.wikipedia.org/wiki/Code_injection" class="external-link">script injection</a>.</p>
<p>If you are using data within queries that are submitted to an SQL database or a
content provider, SQL injection may be an issue. The best defense is to use
@@ -348,60 +354,59 @@ href="#ContentProviders">content providers</a>.
Limiting permissions to read-only or write-only can also reduce the potential
for harm related to SQL injection.</p>
<p>If you cannot use the security features above, we strongly recommend the use
of well-structured data formats and verifying that the data conforms to the
<p>If you can't use the security features above, you should make sure to use
well-structured data formats and verify that the data conforms to the
expected format. While blacklisting of characters or character-replacement can
be an effective strategy, these techniques are error-prone in practice and
be an effective strategy, these techniques are error prone in practice and
should be avoided when possible.</p>
<h2 id="UserData">Handling User Data</h2>
<h2 id="UserData">Handling user data</h2>
<p>In general, the best approach for user data security is to minimize the use of APIs that access
sensitive or personal user data. If you have access to user data and can avoid
storing or transmitting the information, do not store or transmit the data.
Finally, consider if there is a way that your application logic can be
storing or transmitting it, don't store or transmit the data.
Consider if there is a way that your application logic can be
implemented using a hash or non-reversible form of the data. For example, your
application might use the hash of an an email address as a primary key, to
application might use the hash of an email address as a primary key to
avoid transmitting or storing the email address. This reduces the chances of
inadvertently exposing data, and it also reduces the chance of attackers
attempting to exploit your application.</p>
<p>If your application accesses personal information such as passwords or
usernames, keep in mind that some jurisdictions may require you to provide a
privacy policy explaining your use and storage of that data. So following the
user names, keep in mind that some jurisdictions may require you to provide a
privacy policy explaining your use and storage of that data. Following the
security best practice of minimizing access to user data may also simplify
compliance.</p>
<p>You should also consider whether your application might be inadvertently
exposing personal information to other parties such as third-party components
for advertising or third-party services used by your application. If you don't
know why a component or service requires a personal information, don’t
know why a component or service requires personal information, don’t
provide it. In general, reducing the access to personal information by your
application will reduce the potential for problems in this area.</p>
application reduces the potential for problems in this area.</p>
<p>If access to sensitive data is required, evaluate whether that information
must be transmitted to a server, or whether the operation can be performed on
the client. Consider running any code using sensitive data on the client to
avoid transmitting user data.</p>
<p>Also, make sure that you do not inadvertently expose user data to other
application on the device through overly permissive IPC, world writable files,
or network sockets. This is a special case of leaking permission-protected data,
<p>If your app requires access to sensitive data, evaluate whether you need to
transmit it to a server or you can run the operation on
the client. Consider running any code using sensitive data on the client to
avoid transmitting user data. Also, make sure that you do not inadvertently expose user
data to other
applications on the device through overly permissive IPC, world-writable files,
or network sockets. Overly permissive IPC is a special case of leaking permission-protected data,
discussed in the <a href="#RequestingPermissions">Requesting Permissions</a> section.</p>
<p>If a <acronym title="Globally Unique Identifier">GUID</acronym>
is required, create a large, unique number and store it. Do not
use phone identifiers such as the phone number or IMEI which may be associated
is required, create a large, unique number and store it. Don't
use phone identifiers such as the phone number or IMEI, which may be associated
with personal information. This topic is discussed in more detail in the <a
href="http://android-developers.blogspot.com/2011/03/identifying-app-installations.html">Android
Developer Blog</a>.</p>
href="http://android-developers.blogspot.com/2011/03/identifying-app-installations.html"
>Android Developer Blog</a>.</p>
<p>Be careful when writing to on-device logs.
In Android, logs are a shared resource, and are available
In Android, logs are a shared resource and are available
to an application with the {@link android.Manifest.permission#READ_LOGS} permission.
Even though the phone log data
is temporary and erased on reboot, inappropriate logging of user information
@@ -414,19 +419,23 @@ could inadvertently leak user data to other applications.</p>
<h2 id="WebView">Using WebView</h2>
<p>Because {@link android.webkit.WebView} consumes web content that can include HTML and JavaScript,
<p>Because {@link android.webkit.WebView} consumes web content that can include HTML
and JavaScript,
improper use can introduce common web security issues such as <a
href="http://en.wikipedia.org/wiki/Cross_site_scripting">cross-site-scripting</a>
href="http://en.wikipedia.org/wiki/Cross_site_scripting" class="external-link">
cross-site-scripting</a>
(JavaScript injection). Android includes a number of mechanisms to reduce
the scope of these potential issues by limiting the capability of {@link android.webkit.WebView} to
the scope of these potential issues by limiting the capability of
{@link android.webkit.WebView} to
the minimum functionality required by your application.</p>
<p>If your application does not directly use JavaScript within a {@link android.webkit.WebView}, do
<em>not</em> call {@link android.webkit.WebSettings#setJavaScriptEnabled setJavaScriptEnabled()}.
<p>If your application doesn't directly use JavaScript within a {@link android.webkit.WebView},
<em>do not</em> call
{@link android.webkit.WebSettings#setJavaScriptEnabled setJavaScriptEnabled()}.
Some sample code uses this method, which you might repurpose in production
application, so remove that method call if it's not required. By default,
{@link android.webkit.WebView} does
not execute JavaScript so cross-site-scripting is not possible.</p>
not execute JavaScript, so cross-site-scripting is not possible.</p>
<p>Use {@link android.webkit.WebView#addJavascriptInterface
addJavaScriptInterface()} with
@@ -441,55 +450,55 @@ addJavaScriptInterface()} only to JavaScript that is contained within your appli
<p>If your application accesses sensitive data with a
{@link android.webkit.WebView}, you may want to use the
{@link android.webkit.WebView#clearCache clearCache()} method to delete any files stored
locally. Server-side
headers like <code>no-cache</code> can also be used to indicate that an application should
locally. You can also use server-side
headers such as <code>no-cache</code> to indicate that an application should
not cache particular content.</p>
<p>Devices running platforms older than Android 4.4 (API level 19)
use a version of {@link android.webkit webkit} that has a number of security issues.
As a workaround, if your app is running on these devices, it
should confirm that {@link android.webkit.WebView} objects display only trusted
content. You should also use the updatable security {@link
java.security.Provider Provider} object to make sure your app isn’t exposed to
potential vulnerabilities in SSL, as described in <a
must confirm that {@link android.webkit.WebView} objects display only trusted
content. To make sure your app isn’t exposed to
potential vulnerabilities in SSL, use the updatable security {@link
java.security.Provider Provider} object as described in <a
href="{@docRoot}training/articles/security-gms-provider.html">Updating Your
Security Provider to Protect Against SSL Exploits</a>. If your application must
render content from the open web, consider providing your own renderer so
you can keep it up to date with the latest security patches.</p>
<h3 id="Credentials">Handling Credentials</h3>
<h3 id="Credentials">Handling credentials</h3>
<p>In general, we recommend minimizing the frequency of asking for user
credentials&mdash;to make phishing attacks more conspicuous, and less likely to be
successful. Instead use an authorization token and refresh it.</p>
<p>To make phishing attacks more conspicuous and less likely to be
successful, minimize the frequency of asking for user
credentials. Instead use an authorization token and refresh it.</p>
<p>Where possible, username and password should not be stored on the device.
Instead, perform initial authentication using the username and password
supplied by the user, and then use a short-lived, service-specific
<p>Where possible, don't store user names and passwords on the device.
Instead, perform initial authentication using the user name and password
supplied by the user, and then use a short-lived, service-specific
authorization token.</p>
<p>Services that will be accessible to multiple applications should be accessed
<p>Services that are accessible to multiple applications should be accessed
using {@link android.accounts.AccountManager}. If possible, use the
{@link android.accounts.AccountManager} class to invoke a cloud-based service and do not store
{@link android.accounts.AccountManager} class to invoke a cloud-based service and don't store
passwords on the device.</p>
<p>After using {@link android.accounts.AccountManager} to retrieve an
{@link android.accounts.Account}, {@link android.accounts.Account#CREATOR}
before passing in any credentials, so that you do not inadvertently pass
{@link android.accounts.Account}, use {@link android.accounts.Account#CREATOR}
before passing in any credentials so that you do not inadvertently pass
credentials to the wrong application.</p>
<p>If credentials are to be used only by applications that you create, then you
can verify the application which accesses the {@link android.accounts.AccountManager} using
<p>If credentials are used only by applications that you create, you
can verify the application that accesses the {@link android.accounts.AccountManager} using
{@link android.content.pm.PackageManager#checkSignatures checkSignature()}.
Alternatively, if only one application will use the credential, you might use a
Alternatively, if only one application uses the credential, you might use a
{@link java.security.KeyStore} for storage.</p>
<h2 id="Crypto">Using Cryptography</h2>
<h2 id="Crypto">Using cryptography</h2>
<p>In addition to providing data isolation, supporting full-filesystem
encryption, and providing secure communications channels, Android provides a
@@ -500,21 +509,21 @@ implementation that can support your use case. If you need to securely
retrieve a file from a known location, a simple HTTPS URI may be adequate and
requires no knowledge of cryptography. If you need a secure
tunnel, consider using {@link javax.net.ssl.HttpsURLConnection} or
{@link javax.net.ssl.SSLSocket}, rather than writing your own protocol.</p>
{@link javax.net.ssl.SSLSocket} rather than writing your own protocol.</p>
<p>If you do find yourself needing to implement your own protocol, we strongly
recommend that you <em>not</em> implement your own cryptographic algorithms. Use
<p>If you do need to implement your own protocol, you should <em>not</em>
implement your own cryptographic algorithms. Use
existing cryptographic algorithms such as those in the implementation of AES or
RSA provided in the {@link javax.crypto.Cipher} class.</p>
<p>Use a secure random number generator, {@link java.security.SecureRandom},
to initialize any cryptographic keys, {@link javax.crypto.KeyGenerator}.
to initialize any cryptographic keys generated by {@link javax.crypto.KeyGenerator}.
Use of a key that is not generated with a secure random
number generator significantly weakens the strength of the algorithm, and may
number generator significantly weakens the strength of the algorithm and may
allow offline attacks.</p>
<p>If you need to store a key for repeated use, use a mechanism like
{@link java.security.KeyStore} that
<p>If you need to store a key for repeated use, use a mechanism, such as
{@link java.security.KeyStore}, that
provides a mechanism for long term storage and retrieval of cryptographic
keys.</p>
@@ -522,10 +531,10 @@ keys.</p>
<h2 id="IPC">Using Interprocess Communication</h2>
<h2 id="IPC">Using interprocess communication</h2>
<p>Some apps attempt to implement IPC using traditional Linux
techniques such as network sockets and shared files. We strongly encourage you to instead
techniques such as network sockets and shared files. However, you should instead
use Android system functionality for IPC such as {@link android.content.Intent},
{@link android.os.Binder} or {@link android.os.Messenger} with a {@link
android.app.Service}, and {@link android.content.BroadcastReceiver}.
@@ -535,19 +544,19 @@ mechanism.</p>
<p>Many of the security elements are shared across IPC mechanisms.
If your IPC mechanism is not intended for use by other applications, set the
{@code android:exported} attribute to {@code "false"} in the component's manifest element,
{@code android:exported} attribute to {@code false} in the component's manifest element,
such as for the <a
href="{@docRoot}guide/topics/manifest/service-element.html#exported">{@code <service>}</a>
href="{@docRoot}guide/topics/manifest/service-element.html#exported">{@code &lt;service&gt;}</a>
element. This is useful for applications that consist of multiple processes
within the same UID, or if you decide late in development that you do not
actually want to expose functionality as IPC but you don’t want to rewrite
within the same UID or if you decide late in development that you don't
actually want to expose functionality as IPC, but you don’t want to rewrite
the code.</p>
<p>If your IPC is intended to be accessible to other applications, you can
<p>If your IPC is accessible to other applications, you can
apply a security policy by using the <a
href="{@docRoot}guide/topics/manifest/permission-element.html">{@code <permission>}</a>
href="{@docRoot}guide/topics/manifest/permission-element.html">{@code &lt;permission>}</a>
element. If IPC is between your own separate apps that are signed with the same key,
it is preferable to use {@code "signature"} level permission in the <a
it is preferable to use {@code signature} level permission in the <a
href="{@docRoot}guide/topics/manifest/permission-element.html#plevel">{@code
android:protectionLevel}</a>.</p>
@@ -556,31 +565,42 @@ android:protectionLevel}</a>.</p>
<h3>Using intents</h3>
<p>Intents are the preferred mechanism for asynchronous IPC in Android.
<p>For activities and broadcast receivers, intents are the preferred mechanism for
asynchronous IPC in Android.
Depending on your application requirements, you might use {@link
android.content.Context#sendBroadcast sendBroadcast()}, {@link
android.content.Context#sendOrderedBroadcast sendOrderedBroadcast()},
or an explicit intent to a specific application component.</p>
<p>Note that ordered broadcasts can be “consumed” by a recipient, so they
may not be delivered to all applications. If you are sending an intent that must be delivered
to a specific receiver, then you must use an explicit intent that declares the receiver
by nameintent.</p>
<p class="caution"><strong>Caution:</strong> If you use an intent to bind to a
{@link android.app.Service}, ensure that your app is secure by using an
<a href="{@docRoot}guide/components/intents-filters.html#Types">explicit</a>
intent. Using an implicit intent to start a service is a
security hazard because you can't be certain what service will respond to the intent,
and the user can't see which service starts. Beginning with Android 5.0 (API level 21),
the system
throws an exception if you call {@link android.content.Context#bindService bindService()}
with an implicit intent.</p>
<p>Senders of an intent can verify that the recipient has a permission
specifying a non-Null permission with the method call. Only applications with that
permission will receive the intent. If data within a broadcast intent may be
<p>Note that ordered broadcasts can be <em>consumed</em> by a recipient, so they
may not be delivered to all applications. If you are sending an intent that must be delivered
to a specific receiver, you must use an explicit intent that declares the receiver
by name.</p>
<p>Senders of an intent can verify that the recipient has permission
by specifying a non-null permission with the method call. Only applications with that
permission receive the intent. If data within a broadcast intent may be
sensitive, you should consider applying a permission to make sure that
malicious applications cannot register to receive those messages without
appropriate permissions. In those circumstances, you may also consider
malicious applications can't register to receive those messages without
appropriate permissions. In those circumstances, you may also consider
invoking the receiver directly, rather than raising a broadcast.</p>
<p class="note"><strong>Note:</strong> Intent filters should not be considered
a security feature&mdash;components
a security feature. Components
can be invoked with explicit intents and may not have data that would conform to the intent
filter. You should perform input validation within your intent receiver to
filter. To
confirm that it is properly formatted for the invoked receiver, service, or
activity.</p>
activity, perform input validation within your intent receiver.</p>
@@ -589,26 +609,32 @@ activity.</p>
<p>A {@link android.app.Service} is often used to supply functionality for other applications to
use. Each service class must have a corresponding <a
href="{@docRoot}guide/topics/manifest/service-element.html">{@code <service>}</a> declaration in its
href="{@docRoot}guide/topics/manifest/service-element.html">{@code <service>}</a>
declaration in its
manifest file.</p>
<p>By default, services are not exported and cannot be invoked by any other
application. However, if you add any intent filters to the service declaration, then it is exported
application. However, if you add any intent filters to the service declaration, it is exported
by default. It's best if you explicitly declare the <a
href="{@docRoot}guide/topics/manifest/service-element.html#exported">{@code
android:exported}</a> attribute to be sure it behaves as you'd like.
Services can also be protected using the <a
href="{@docRoot}guide/topics/manifest/service-element.html#prmsn">{@code android:permission}</a>
attribute. By doing so, other applications will need to declare
attribute. By doing so, other applications need to declare
a corresponding <code><a
href="{@docRoot}guide/topics/manifest/uses-permission-element.html">&lt;uses-permission&gt;</a>
</code> element in their own manifest to be
able to start, stop, or bind to the service.</p>
<p class="note"><strong>Note:</strong> If your app targets Android 5.0 (API level 21) or later,
you should use the {@link android.app.job.JobScheduler} to execute background
services. For more information about {@link android.app.job.JobScheduler}, see its
{@link android.app.job.JobScheduler API-reference documentation}.</p>
<p>A service can protect individual IPC calls into it with permissions, by
calling {@link android.content.Context#checkCallingPermission
checkCallingPermission()} before executing
the implementation of that call. We generally recommend using the
the implementation of that call. You should use the
declarative permissions in the manifest, since those are less prone to
oversight.</p>
@@ -620,24 +646,24 @@ oversight.</p>
preferred mechanism for RPC-style IPC in Android. They provide a well-defined
interface that enables mutual authentication of the endpoints, if required.</p>
<p>We strongly encourage designing interfaces in a manner that does not require
interface specific permission checks. {@link android.os.Binder} and
<p>You should design your app interfaces in a manner that does not require
interface-specific permission checks. {@link android.os.Binder} and
{@link android.os.Messenger} objects are not declared within the
application manifest, and therefore you cannot apply declarative permissions
directly to them. They generally inherit permissions declared in the
application manifest for the {@link android.app.Service} or {@link
android.app.Activity} within which they are
implemented. If you are creating an interface that requires authentication
and/or access controls, those controls must be
explicitly added as code in the {@link android.os.Binder} or {@link android.os.Messenger}
and/or access controls, you must explicitly add those controls
as code in the {@link android.os.Binder} or {@link android.os.Messenger}
interface.</p>
<p>If providing an interface that does require access controls, use {@link
<p>If you are providing an interface that does require access controls, use {@link
android.content.Context#checkCallingPermission checkCallingPermission()}
to verify whether the
caller has a required permission. This is especially important
before accessing a service on behalf of the caller, as the identify of your
application is passed to other interfaces. If invoking an interface provided
application is passed to other interfaces. If you are invoking an interface provided
by a {@link android.app.Service}, the {@link
android.content.Context#bindService bindService()}
invocation may fail if you do not have permission to access the given service.
@@ -660,8 +686,8 @@ application. If your {@link android.content.BroadcastReceiver}
is intended for use by other applications, you
may want to apply security permissions to receivers using the <code><a
href="{@docRoot}guide/topics/manifest/receiver-element.html">
&lt;receiver&gt;</a></code> element within the application manifest. This will
prevent applications without appropriate permissions from sending an intent to
&lt;receiver&gt;</a></code> element within the application manifest. This
prevents applications without appropriate permissions from sending an intent to
the {@link android.content.BroadcastReceiver}.</p>
@@ -671,57 +697,58 @@ the {@link android.content.BroadcastReceiver}.</p>
<h2 id="DynamicCode">Dynamically Loading Code</h2>
<h2 id="DynamicCode">Dynamically loading code</h2>
<p>We strongly discourage loading code from outside of your application APK.
Doing so significantly increases the likelihood of application compromise due
to code injection or code tampering. It also adds complexity around version
management and application testing. Finally, it can make it impossible to
to code injection or code tampering. It also adds complexity around version
management and application testing. It can also make it impossible to
verify the behavior of an application, so it may be prohibited in some
environments.</p>
<p>If your application does dynamically load code, the most important thing to
keep in mind about dynamically loaded code is that it runs with the same
security permissions as the application APK. The user made a decision to
install your application based on your identity, and they are expecting that
keep in mind about dynamically-loaded code is that it runs with the same
security permissions as the application APK. The user makes a decision to
install your application based on your identity, and the user expects that
you provide any code run within the application, including code that is
dynamically loaded.</p>
<p>The major security risk associated with dynamically loading code is that the
code needs to come from a verifiable source. If the modules are included
directly within your APK, then they cannot be modified by other applications.
directly within your APK, they cannot be modified by other applications.
This is true whether the code is a native library or a class being loaded using
{@link dalvik.system.DexClassLoader}. We have seen many instances of applications
attempting to load code from insecure locations, such as downloaded from the
network over unencrypted protocols or from world writable locations such as
{@link dalvik.system.DexClassLoader}. Many applications
attempt to load code from insecure locations, such as downloaded from the
network over unencrypted protocols or from world-writable locations such as
external storage. These locations could allow someone on the network to modify
the content in transit, or another application on a users device to modify the
content on the device, respectively.</p>
the content in transit or another application on a user's device to modify the
content on the device.</p>
<h2 id="Dalvik">Security in a Virtual Machine</h2>
<h2 id="Dalvik">Security in a virtual machine</h2>
<p>Dalvik is Android's runtime virtual machine (VM). Dalvik was built specifically for Android,
but many of the concerns regarding secure code in other virtual machines also apply to Android.
In general, you shouldn't concern yourself with security issues relating to the virtual machine.
Your application runs in a secure sandbox environment, so other processes on the system cannnot
Your application runs in a secure sandbox environment, so other processes on the system can't
access your code or private data.</p>
<p>If you're interested in diving deeper on the subject of virtual machine security,
we recommend that you familiarize yourself with some
<p>If you're interested in learning more about virtual machine security,
familiarize yourself with some
existing literature on the subject. Two of the more popular resources are:
<ul>
<li><a href="http://www.securingjava.com/toc.html">
http://www.securingjava.com/toc.html</a></li>
<li><a href="http://www.securingjava.com/toc.html" class="external-link">
Securing Java</a></li>
<li><a
href="https://www.owasp.org/index.php/Java_Security_Resources">
https://www.owasp.org/index.php/Java_Security_Resources</a></li>
href="https://www.owasp.org/index.php/Category:Java#tab=Related_3rd_Party_Projects"
class="external-link">
Related 3rd party Projects</a></li>
</ul></p>
<p>This document is focused on the areas which are Android specific or
<p>This document focuses on areas that are Android specific or
different from other VM environments. For developers experienced with VM
programming in other environments, there are two broad issues that may be
different about writing apps for Android:
@@ -742,21 +769,19 @@ because that code might be modified to include malicious behavior.</li>
<h2 id="Native">Security in Native Code</h2>
<h2 id="Native">Security in native code</h2>
<p>In general, we encourage developers to use the Android SDK for
<p>In general, you should use the Android SDK for
application development, rather than using native code with the
<a href="{@docRoot}tools/sdk/ndk/index.html">Android NDK</a>. Applications built
with native code are more complex, less portable, and more like to include
common memory corruption errors such as buffer overflows.</p>
common memory-corruption errors such as buffer overflows.</p>
<p>Android is built using the Linux kernel and being familiar with Linux
development security best practices is especially useful if you are going to
use native code. Linux security practices are beyond the scope of this document,
but one of the most popular resources is “Secure Programming for
Linux and Unix HOWTO”, available at <a
href="http://www.dwheeler.com/secure-programs">
http://www.dwheeler.com/secure-programs</a>.</p>
<p>Android is built using the Linux kernel, and being familiar with Linux
development security best practices is especially useful if you are
using native code. Linux security practices are beyond the scope of this document,
but one of the most popular resources is <a href="http://www.dwheeler.com/secure-programs"
class="external-link">Secure Programming HOWTO - Creating Secure Software</a>.</p>
<p>An important difference between Android and most Linux environments is the
Application Sandbox. On Android, all applications run in the Application
@@ -765,6 +790,5 @@ good way to think about it for developers familiar with Linux is to know that
every application is given a unique <acronym title="User Identifier">UID</acronym>
with very limited permissions. This is discussed in more detail in the <a
href="http://source.android.com/tech/security/index.html">Android Security
Overview</a> and you should be familiar with application permissions even if
Overview</a>, and you should be familiar with application permissions even if
you are using native code.</p>

130
docs/html/training/location/display-address.jd
View File

@@ -7,11 +7,11 @@ trainingnavtop=true
<h2>This lesson teaches you how to</h2>
<ol>
<li><a href="#connect">Get a Geographic Location</a></li>
<li><a href="#fetch-address">Define an Intent Service to Fetch the
Address</a></li>
<li><a href="#start-intent">Start the Intent Service</a></li>
<li><a href="#result-receiver">Receive the Geocoding Results</a></li>
<li><a href="#connect">Get a geographic location</a></li>
<li><a href="#fetch-address">Define an intent service to fetch the
address</a></li>
<li><a href="#start-intent">Start the intent service</a></li>
<li><a href="#result-receiver">Receive the geocoding results</a></li>
</ol>
<h2>You should also read</h2>
@@ -58,7 +58,7 @@ trainingnavtop=true
convert a geographic location to an address. The method returns an estimated
street address corresponding to a given latitude and longitude.</p>
<h2 id="connect">Get a Geographic Location</h2>
<h2 id="connect">Get a geographic location</h2>
<p>The last known location of the device is a useful starting point for the
address lookup feature. The lesson on
@@ -69,12 +69,12 @@ trainingnavtop=true
<a href="{@docRoot}reference/com/google/android/gms/location/FusedLocationProviderApi.html">fused
location provider</a> to find the latest location of the device.</p>
<p>To access the fused location provider, you need to create an instance of the
<p>To access the fused location provider, create an instance of the
Google Play services API client. To learn how to connect your client, see
<a href="{@docRoot}training/location/retrieve-current.html#play-services">Connect
to Google Play Services</a>.</p>
<p>In order for the fused location provider to retrieve a precise street
<p>To enable the fused location provider to retrieve a precise street
address, set the location permission in your app manifest to
{@code ACCESS_FINE_LOCATION}, as shown in the following example:</p>
@@ -86,12 +86,12 @@ trainingnavtop=true
&lt;/manifest&gt;
</pre>
<h2 id="fetch-address">Define an Intent Service to Fetch the Address</h2>
<h2 id="fetch-address">Define an intent service to fetch the address</h2>
<p>The {@link android.location.Geocoder#getFromLocation getFromLocation()}
method provided by the {@link android.location.Geocoder} class accepts a
latitude and longitude, and returns a list of addresses. The method is
synchronous, and may take a long time to do its work, so you should not call
latitude and longitude and returns a list of addresses. The method is
synchronous and may take a long time to do its work, so you should not call
it from the main, user interface (UI) thread of your app.</p>
<p>The {@link android.app.IntentService IntentService} class provides a
@@ -100,23 +100,23 @@ trainingnavtop=true
Note that the {@link android.os.AsyncTask AsyncTask} class also allows you to
perform background operations, but it's designed for short operations. An
{@link android.os.AsyncTask AsyncTask} shouldn't keep a reference to the UI if
the activity is recreated, for example when the device is rotated. In
the activity is re-created, such as when the device is rotated. In
contrast, an {@link android.app.IntentService IntentService} doesn't need to
be cancelled when the activity is rebuilt.</p>
<p>Define a {@code FetchAddressIntentService} class that extends
{@link android.app.IntentService}. This class is your address lookup service.
The intent service handles an intent asynchronously on a worker thread, and
The intent service handles an intent asynchronously on a worker thread and
stops itself when it runs out of work. The intent extras provide the data
needed by the service, including a {@link android.location.Location} object
for conversion to an address, and a {@link android.os.ResultReceiver} object
for conversion to an address and a {@link android.os.ResultReceiver} object
to handle the results of the address lookup. The service uses a {@link
android.location.Geocoder} to fetch the address for the location, and sends
android.location.Geocoder} to fetch the address for the location and sends
the results to the {@link android.os.ResultReceiver}.</p>
<h3>Define the Intent Service in your App Manifest</h3>
<h3>Define the intent service in your app manifest</h3>
<p>Add an entry to your app manifest defining the intent service:</p>
<p>Add an entry to your app manifest that defines the intent service, as shown here:</p>
<pre>
&lt;manifest xmlns:android="http://schemas.android.com/apk/res/android"
@@ -131,26 +131,26 @@ trainingnavtop=true
&lt;/manifest&gt;
</pre>
<p class="note"><strong>Note:</strong> The {@code <service>} element in
the manifest doesn't need to include an intent filter, because your main
<p class="note"><strong>Note:</strong> The {@code &lt;service&gt;} element in
the manifest doesn't need to include an intent filter because your main
activity creates an explicit intent by specifying the name of the class to use
for the intent.</p>
<h3>Create a Geocoder</h3>
<h3>Create a geocoder</h3>
<p>The process of converting a geographic location to an address is called
<em>reverse geocoding</em>. To perform the main work of the intent service,
that is, your reverse geocoding request, implement
<em>reverse geocoding</em>. To perform the main work of the intent service (your reverse
geocoding request), implement
{@link android.app.IntentService#onHandleIntent onHandleIntent()} within the
{@code FetchAddressIntentService} class. Create a
{@link android.location.Geocoder} object to handle the reverse geocoding.</p>
<p>A locale represents a specific geographical or linguistic region. Locale
objects are used to adjust the presentation of information, such as numbers or
dates, to suit the conventions in the region represented by the locale. Pass a
objects adjust the presentation of information, such as numbers or
dates, to suit the conventions in the region that is represented by the locale. Pass a
<a href="{@docRoot}reference/java/util/Locale.html">{@code Locale}</a> object
to the {@link android.location.Geocoder} object, to ensure that the resulting
address is localized to the user's geographic region.</p>
to the {@link android.location.Geocoder} object to ensure that the resulting
address is localized to the user's geographic region. Here is an example:</p>
<pre>
&#64;Override
@@ -162,7 +162,7 @@ protected void onHandleIntent(Intent intent) {
<h3 id="retrieve-street-address">Retrieve the street address data</h3>
<p>The next step is to retrieve the street address from the geocoder, handle
<p>You can now retrieve the street address from the geocoder, handle
any errors that may occur, and send the results back to the activity that
requested the address. To report the results of the geocoding
process, you need two numeric constants that indicate success or failure.
@@ -185,32 +185,34 @@ public final class Constants {
<p>To get a street address corresponding to a geographical location, call
{@link android.location.Geocoder#getFromLocation getFromLocation()},
passing it the latitude and longitude from the location object, and the
maximum number of addresses you want returned. In this case, you want just one
address. The geocoder returns an array of addresses. If no addresses were
passing it the latitude and longitude from the location object and the
maximum number of addresses that you want returned. In this case, you want just one
address. The geocoder returns an array of addresses. If no addresses are
found to match the given location, it returns an empty list. If there is no
backend geocoding service available, the geocoder returns null.</p>
<p>Check for the following errors as shown in the code sample below. If an error
occurs, place the corresponding error message in the {@code errorMessage}
variable, so you can send it back to the requesting activity:</p>
<p>Check for the following errors, as shown in the code sample below:</p>
<ul>
<li><strong>No location data provided</strong> - The intent extras do not
include the {@link android.location.Location} object required for reverse
<li><strong>No location data provided</strong> &ndash; The intent extras do not
include the {@link android.location.Location} object that is required for reverse
geocoding.</li>
<li><strong>Invalid latitude or longitude used</strong> - The latitude
and/or longitude values provided in the {@link android.location.Location}
<li><strong>Invalid latitude or longitude used</strong> &ndash; The latitude
and/or longitude values that are provided in the {@link android.location.Location}
object are invalid.</li>
<li><strong>No geocoder available</strong> - The background geocoding service
is not available, due to a network error or IO exception.</li>
<li><strong>Sorry, no address found</strong> - The geocoder could not find an
<li><strong>No geocoder available</strong> &ndash; The background geocoding service
is not available due to a network error or IO exception.</li>
<li><strong>Sorry, no address found</strong> &ndash; The geocoder can't find an
address for the given latitude/longitude.</li>
</ul>
<p>If an error
occurs, place the corresponding error message in the {@code errorMessage}
variable so that you can send it back to the requesting activity.
<p>To get the individual lines of an address object, use the
{@link android.location.Address#getAddressLine getAddressLine()}
method provided by the {@link android.location.Address} class. Then join the
method that is provided by the {@link android.location.Address} class. Join the
lines into a list of address fragments ready to return to the activity that
requested the address.</p>
@@ -220,7 +222,7 @@ public final class Constants {
results consist of the previously-mentioned numeric success/failure code and
a string. In the case of a successful reverse geocoding, the string contains
the address. In the case of a failure, the string contains the error message,
as shown in the code sample below:</p>
as shown in this code sample:</p>
<pre>
&#64;Override
@@ -280,18 +282,18 @@ protected void onHandleIntent(Intent intent) {
<h3 id="return-address">Return the address to the requestor</h3>
<p>The final thing the intent service must do is send the address back to a
<p>The final action that the intent service must complete is sending the address back to a
{@link android.os.ResultReceiver} in the activity that started the service.
The {@link android.os.ResultReceiver} class allows you to send a
numeric result code as well as a message containing the result data. The
numeric code is useful for reporting the success or failure of the geocoding
request. In the case of a successful reverse geocoding, the message contains
the address. In the case of a failure, the message contains some text
describing the reason for failure.</p>
describing the reason for the failure.</p>
<p>You have already retrieved the address from the geocoder, trapped any errors
that may occur, and called the {@code deliverResultToReceiver()} method. Now
you need to define the {@code deliverResultToReceiver()} method that sends
that may occur, and called the {@code deliverResultToReceiver()} method, so now
you must define the {@code deliverResultToReceiver()} method that sends
a result code and message bundle to the result receiver.</p>
<p>For the result code, use the value that you've passed to the
@@ -299,7 +301,7 @@ protected void onHandleIntent(Intent intent) {
To construct the message bundle, concatenate the {@code RESULT_DATA_KEY}
constant from your {@code Constants} class (defined in
<a href="#retrieve-street-address">Retrieve the street address data</a>) and
the value in the {@code message} parameter passed to the
the value in the {@code message} parameter that is passed to the
{@code deliverResultToReceiver()} method, as shown in the following sample:
</p>
@@ -315,26 +317,26 @@ public class FetchAddressIntentService extends IntentService {
}
</pre>
<h2 id="start-intent">Start the Intent Service</h2>
<h2 id="start-intent">Start the intent service</h2>
<p>The intent service, as defined in the previous section, runs in the
background and is responsible for fetching the address corresponding to a
background and fetches the address corresponding to a
given geographic location. When you start the service, the Android framework
instantiates and starts the service if it isn't already running, and creates a
process if needed. If the service is already running then it remains running.
instantiates and starts the service if it isn't already running, and it creates a
process if needed. If the service is already running, it remains running.
Because the service extends {@link android.app.IntentService IntentService},
it shuts down automatically when all intents have been processed.</p>
it shuts down automatically after all intents are processed.</p>
<p>Start the service from your app's main activity,
<p>Start the service from your app's main activity
and create an {@link android.content.Intent} to pass data to the service. You
need an <em>explicit</em> intent, because you want only your service
need an <em>explicit</em> intent because you want only your service
to respond to the intent. For more information, see
<a href="{@docRoot}guide/components/intents-filters.html#Types">Intent
Types</a>.</p>
<p>To create an explicit intent, specify the name of the
class to use for the service: {@code FetchAddressIntentService.class}.
Pass two pieces of information in the intent extras:</p>
Pass this information in the intent extras:</p>
<ul>
<li>A {@link android.os.ResultReceiver} to handle the results of the address
@@ -362,6 +364,12 @@ public class MainActivity extends ActionBarActivity implements
}
</pre>
<p class="caution"><strong>Caution</strong>: To ensure that your app is secure, always use an
explicit intent when starting a {@link android.app.Service} and do not declare intent filters for
your services. Using an implicit intent to start a service is a security hazard because you cannot
be certain of the service that will respond to the intent, and the user cannot see which service
starts.</p>
<p>Call the above {@code startIntentService()} method when the
user takes an action that requires a geocoding address lookup. For example,
the user may press a <em>Fetch address</em> button on your app's UI. Before
@@ -391,7 +399,7 @@ public void fetchAddressButtonHandler(View view) {
app's UI. The following code snippet shows the call to the
{@code startIntentService()} method in the
<a href="{@docRoot}reference/com/google/android/gms/common/api/GoogleApiClient.ConnectionCallbacks.html#onConnected(android.os.Bundle)">{@code onConnected()}</a>
callback provided by the Google API Client:</p>
callback that is provided by the Google API Client:</p>
<pre>
public class MainActivity extends ActionBarActivity implements
@@ -420,9 +428,9 @@ public class MainActivity extends ActionBarActivity implements
}
</pre>
<h2 id="result-receiver">Receive the Geocoding Results</h2>
<h2 id="result-receiver">Receive the geocoding results</h2>
<p>The intent service has handled the geocoding request, and uses a
<p>After the intent service handles the geocoding request, it uses a
{@link android.os.ResultReceiver} to return the results to the activity that
made the request. In the activity that makes the request, define an
{@code AddressResultReceiver} that extends {@link android.os.ResultReceiver}
@@ -430,14 +438,14 @@ public class MainActivity extends ActionBarActivity implements
<p>The result includes a numeric result code (<code>resultCode</code>) as well
as a message containing the result data (<code>resultData</code>). If the
reverse geocoding process was successful, the <code>resultData</code> contains
reverse geocoding process is successful, the <code>resultData</code> contains
the address. In the case of a failure, the <code>resultData</code> contains
text describing the reason for failure. For details of the possible errors,
text describing the reason for the failure. For details of the possible errors,
see <a href="#return-address">Return the address to the requestor</a>.</p>
<p>Override the
{@link android.os.ResultReceiver#onReceiveResult onReceiveResult()} method
to handle the results delivered to the result receiver, as shown in the
to handle the results that are delivered to the result receiver, as shown in the
following code sample:</p>
<pre>

14
docs/html/training/run-background-service/index.jd
View File

@@ -35,16 +35,22 @@ startpage=true
<!-- ------------------------------------------------------------------------------------------- -->
<p>
Unless you specify otherwise, most of the operations you do in an app run in the foreground on
a special thread called the UI thread. This can cause problems, because long-running operations
will interfere with the responsiveness of your user interface. This annoys your users, and can
a special thread called the UI thread. Long-running foreground operations can cause problems
and interfere with the responsiveness of your user interface, which annoys your users and can
even cause system errors. To avoid this, the Android framework offers several classes that
help you off-load operations onto a separate thread running in the background. The most useful
of these is {@link android.app.IntentService}.
help you off-load operations onto a separate thread that runs in the background. The most
useful of these is {@link android.app.IntentService}.
</p>
<p>
This class describes how to implement an {@link android.app.IntentService}, send it work
requests, and report its results to other components.
</p>
<p class="note"><strong>Note:</strong> If your app targets Android 5.0 (API level 21),
you should use {@link android.app.job.JobScheduler} to execute background
services. For more information about this class,
see the {@link android.app.job.JobScheduler} reference documentation.</p>
<h2>Lessons</h2>
<dl>
<dt>