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AI 148812: revise the AppWidget developer guide documentation

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Scott Main
2009-05-13 16:48:13 -07:00
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docs/html/guide/guide_toc.cs
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@@ -95,7 +95,7 @@
</ul>
</li> -->
<!-- <li><a style="color:gray;">Localization</a></li> -->
<li><a href="<?cs var:toroot ?>guide/topics/appwidgets/index.html">AppWidgets</a></li>
<li><a href="<?cs var:toroot ?>guide/topics/appwidgets/index.html">App Widgets</a></li>
</ul>
</li>
@@ -146,7 +146,7 @@
<li class="toggle-list">
<div><a href="<?cs var:toroot ?>guide/practices/ui_guidelines/index.html">UI Guidelines</a></div>
<ul>
<li><a href="<?cs var:toroot ?>guide/practices/ui_guidelines/widget_design.html">Widget Design</a></li>
<li><a href="<?cs var:toroot ?>guide/practices/ui_guidelines/widget_design.html">App Widget Design</a></li>
</ul>
</li>
<li><a href="<?cs var:toroot ?>guide/practices/design/performance.html">Designing for Performance</a></li>

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docs/html/guide/topics/appwidgets/index.jd
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@@ -1,4 +1,4 @@
page.title=AppWidgets
page.title=App Widgets
@jd:body
<div id="qv-wrapper">
@@ -6,131 +6,338 @@ page.title=AppWidgets
<h2>Key classes</h2>
<ol>
<li>{@link android.appwidget.AppWidgetProvider}</li>
<li>{@link android.appwidget.AppWidgetHost}</li>
<li>{@link android.appwidget.AppWidgetProviderInfo}</li>
<li>{@link android.appwidget.AppWidgetManager}</li>
</ol>
<h2>In this document</h2>
<ol>
<li><a href="#Providers">AppWidget Providers</a>
<li><a href="#Basics">The Basics</a></li>
<li><a href="#Manifest">Declaring an App Widget in the Manifest</a></li>
<li><a href="#MetaData">Adding the AppWidgetProviderInfo Metadata</a></li>
<li><a href="#CreatingLayout">Creating the App Widget Layout</a></li>
<li><a href="#AppWidgetProvider">Using the AppWidgetProvider Class</a>
<ol>
<li><a href="#provider_manifest">Declaring a widget in the AndroidManifest</a></li>
<li><a href="#provider_meta_data">Adding the AppWidgetProviderInfo meta-data</a></li>
<li><a href="#provider_AppWidgetProvider">Using the AppWidgetProvider class</a></li>
<li><a href="#provider_configuration">AppWidget Configuration UI</a></li>
<li><a href="#provider_broadcasts">AppWidget Broadcast Intents</a></li>
<li><a href="#ProviderBroadcasts">Receiving App Widget broadcast Intents</a></li>
</ol>
</li>
<li><a href="#Configuring">Creating an App Widget Configuration Activity</a>
<ol>
<li><a href="#UpdatingFromTheConfiguration">Updating the App Widget from
the configuration Activity</a></li>
</ol>
</li>
<li><a href="#Hosts">AppWidget Hosts</a></li>
</ol>
<h2>See also</h2>
<ol>
<li><a href="{@docRoot}guide/practices/ui_guidelines/widget_design.html">App Widget Design
Guidelines</a></li>
<li><a href="http://android-developers.blogspot.com/2009/04/introducing-home-screen-widgets-and.html">Introducing
home screen widgets and the AppWidget framework &raquo;</a></li>
home screen widgets and the AppWidget framework &raquo;</a></li>
</ol>
</div>
</div>
<p>AppWidgets are miniature application views that can be embedded in other applications
(e.g., the Home). These views are called "widgets" and you can publish one with
an "AppWidget provider." An application component that is able to hold other widgets is
called an "AppWidget host."</p>
<p>App Widgets are miniature application views that can be embedded in other applications
(such as the Home screen) and receive periodic updates. These views are referred
to as Widgets in the user interface,
and you can publish one with an App Widget provider. An application component that is
able to hold other App Widgets is called an App Widget host. The screenshot below shows
the Music App Widget.</p>
<img src="{@docRoot}images/appwidget.png" alt="" />
<p>This document describes how to publish an App Widget using an App Widget provider.</p>
<h2 id="Basics">The Basics</h2>
<p>To create an App Widget, you need the following:</p>
<dl>
<dt>{@link android.appwidget.AppWidgetProviderInfo} object</dt>
<dd>Describes the metadata for an App Widget, such as the App Widget's layout, update frequency,
and the AppWidgetProvider class. This should be defined in XML.</dd>
<dt>{@link android.appwidget.AppWidgetProvider} class implementation</dt>
<dd>Defines the basic methods that allow you to programmatically interface with the App Widget,
based on broadcast events. Through it, you will receive broadcasts when the App Widget is updated,
enabled, disabled and deleted.</dd>
<dt>View layout</dt>
<dd>Defines the initial layout for the App Widget, defined in XML.</dd>
</dl>
<p>Additionally, you can implement an App Widget configuration Activity. This is an optional
{@link android.app.Activity} that launches when the user adds your App Widget and allows him or her
to modify App Widget settings at create-time.</p>
<p>The following sections describe how to setup each of these components.</p>
<h2 id="Providers">AppWidget Providers</h2>
<p>Any application can publish widgets. All an application needs to do to publish a widget is
to have a {@link android.content.BroadcastReceiver} that receives the {@link
android.appwidget.AppWidgetManager#ACTION_APPWIDGET_UPDATE AppWidgetManager.ACTION_APPWIDGET_UPDATE} intent,
and provide some meta-data about the widget. Android provides the
{@link android.appwidget.AppWidgetProvider} class, which extends BroadcastReceiver, as a convenience
class to aid in handling the broadcasts.
<h2 id="Manifest">Declaring an App Widget in the Manifest</h2>
<p>First, declare the {@link android.appwidget.AppWidgetProvider} class in your application's
<code>AndroidManifest.xml</code> file. For example:</p>
<h3 id="provider_manifest">Declaring a widget in the AndroidManifest</h3>
<pre>
&lt;receiver android:name="ExampleAppWidgetProvider" >
&lt;intent-filter>
&lt;action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
&lt;/intent-filter>
&lt;meta-data android:name="android.appwidget.provider"
android:resource="@xml/example_appwidget_info" />
&lt;/receiver>
</pre>
<p>First, declare the {@link android.content.BroadcastReceiver} in your application's
<code>AndroidManifest.xml</code> file.
<p>The <code>&lt;receiver&gt;</code> element requires the <code>android:name</code>
attribute, which specifies the {@link android.appwidget.AppWidgetProvider} used
by the App Widget.</p>
{@sample frameworks/base/tests/appwidgets/AppWidgetHostTest/AndroidManifest.xml AppWidgetProvider}
<p>The <code>&lt;intent-filter&gt;</code> element must include an <code>&lt;action></code>
element with the <code>android:name</code> attribute. This attribute specifies
that the {@link android.appwidget.AppWidgetProvider} accepts the {@link
android.appwidget.AppWidgetManager#ACTION_APPWIDGET_UPDATE ACTION_APPWIDGET_UPDATE} broadcast.
This is the only broadcast that you must explicitly declare. The {@link android.appwidget.AppWidgetManager}
automatically sends all other App Widget broadcasts to the AppWidgetProvider as necessary.</p>
<p>
The <code>&lt;receiver&gt;</code> element has the following attributes:
<p>The <code>&lt;meta-data&gt;</code> element specifies the
{@link android.appwidget.AppWidgetProviderInfo} resource and requires the
following attributes:</p>
<ul>
<li><code>android:name</code> - specifies the
{@link android.content.BroadcastReceiver} or {@link android.appwidget.AppWidgetProvider}
class.</li>
<li><code>android:label</code> - specifies the string resource that
will be shown by the widget picker as the label.</li>
<li><code>android:icon</code> - specifies the drawable resource that
will be shown by the widget picker as the icon.</li>
</ul>
<p>
The <code>&lt;intent-filter&gt;</code> element tells the {@link android.content.pm.PackageManager}
that this {@link android.content.BroadcastReceiver} receives the {@link
android.appwidget.AppWidgetManager#ACTION_APPWIDGET_UPDATE AppWidgetManager.ACTION_APPWIDGET_UPDATE} broadcast.
The widget manager will send other broadcasts directly to your widget provider as required.
It is only necessary to explicitly declare that you accept the {@link
android.appwidget.AppWidgetManager#ACTION_APPWIDGET_UPDATE AppWidgetManager.ACTION_APPWIDGET_UPDATE} broadcast.
<p>
The <code>&lt;meta-data&gt;</code> element tells the widget manager which xml resource to
read to find the {@link android.appwidget.AppWidgetProviderInfo} for your widget provider. It has the following
attributes:
<ul>
<li><code>android:name="android.appwidget.provider"</code> - identifies this meta-data
as the {@link android.appwidget.AppWidgetProviderInfo} descriptor.</li>
<li><code>android:resource</code> - is the xml resource to use as that descriptor.</li>
<li><code>android:name</code> - Specifies the metadata name. Use <code>android.appwidget.provider</code>
to identify the data as the {@link android.appwidget.AppWidgetProviderInfo} descriptor.</li>
<li><code>android:resource</code> - Specifies the {@link android.appwidget.AppWidgetProviderInfo}
resource location.</li>
</ul>
<h3 id="provider_meta_data">Adding the AppWidgetProviderInfo meta-data</h3>
<h2 id="MetaData">Adding the AppWidgetProviderInfo Metadata</h2>
<p>For a widget, the values in the {@link android.appwidget.AppWidgetProviderInfo} structure are supplied
in an XML resource. In the example above, the xml resource is referenced with
<code>android:resource="@xml/appwidget_info"</code>. That XML file would go in your application's
directory at <code>res/xml/appwidget_info.xml</code>. Here is a simple example.
<p>The {@link android.appwidget.AppWidgetProviderInfo} defines the essential
qualities of an App Widget, such as its minimum layout dimensions, its initial layout resource,
how often to update the App Widget, and (optionally) a configuration Activity to launch at create-time.
Define the AppWidgetProviderInfo object in an XML resource using a single
<code>&lt;appwidget-provider></code> element and save it in the project's <code>res/xml/</code>
folder.</p>
{@sample frameworks/base/tests/appwidgets/AppWidgetHostTest/res/xml/appwidget_info.xml AppWidgetProviderInfo}
<p>For example:</p>
<p>The attributes are as documented in the
{@link android.appwidget.AppWidgetProviderInfo} class.
<pre>
&lt;appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
android:minWidth="294dp" &lt;!-- density-independent pixels --&gt;
android:minHeight="72dp"
android:updatePeriodMillis="86400000" &lt;!-- once per day --&gt;
android:initialLayout="@layout/example_appwidget"
android:configure="com.example.android.ExampleAppWidgetConfigure" >
&lt;/appwidget-provider>
</pre>
<p>Here's a summary of the <code>&lt;appwidget-provider></code> attributes:</p>
<ul>
<li>The values for the <code>minWidth</code> and <code>minHeight</code> attributes specify the minimum
area required by the App Widget's layout.
<p>The default Home screen positions App Widgets in its window based on a grid of
cells that have a defined height and width. If the values for an App Widget's minimum width
or height don't match the dimensions of the cells,
then the App Widget dimensions round <em>up</em> to the nearest cell size.
(See the <a href="{@docRoot}guide/practices/ui_guidelines/widget_design.html">App Widget Design
Guidelines</a> for more information on the Home screen cell sizes.)</p>
<p>Because the Home screen's layout orientation (and thus, the cell sizes) can change,
as a rule of thumb, you should assume the worst-case cell size of 74 pixels for the height
<em>and</em> width of a cell. However, you must subtract 2 from the final dimension to account
for any integer rounding errors that occur in the pixel count. To find your minimum width
and height in density-independent pixels (dp), use this formula:<br/>
<code>(number of cells * 74) - 2</code><br/>
Following this formula, you should use 72 dp for a height of one cell, 294 dp and for a width of four cells.</p>
</li>
<li>The <code>updatePerdiodMillis</code> attribute defines how often the App Widget framework should
request an update from the {@link android.appwidget.AppWidgetProvider} by calling the
{@link android.appwidget.AppWidgetProvider#onUpdate(Context,AppWidgetManager,int[])
onUpdate()} method. The actual update is not guaranteed to occur exactly on time with this value
and we suggest updating as infrequently as possible&mdash;perhaps no more than once an hour to
conserve the battery. You might also allow the user to adjust the frequency in a
configuration&mdash;some people might want a stock ticker to update every 15 minutes, or maybe
only four times a day.</li>
<li>The <code>initialLayout</code> attribute points to the layout resource that defines the
App Widget layout.</li>
<li>The <code>configure</code> attribute defines the {@link android.app.Activity} to launch when
the user adds the App Widget, in order for him or her to configure App Widget properties. This is optional
(read <a href="#Configuring">Creating an App Widget Configuration Activity</a> below).</li>
</ul>
<p>See the {@link android.appwidget.AppWidgetProviderInfo} class for more information on the
attributes accepted by the <code>&lt;appwidget-provider></code> element.</p>
<h3 id="provider_AppWidgetProvider">Using the AppWidgetProvider class</h3>
<h2 id="CreatingLayout">Creating the App Widget Layout</h2>
<p>The AppWidgetProvider class is the easiest way to handle the widget provider intent broadcasts.
See the <code>src/com/example/android/apis/appwidget/ExampleAppWidgetProvider.java</code>
sample class in ApiDemos for an example.
<p>You must define an initial layout for your App Widget in XML and save it in the project's
<code>res/layout/</code> directory. You can design your App Widget using the View objects listed
below, but before you begin designing your App Widget, please read and understand the
<a href="{@docRoot}guide/practices/ui_guidelines/widget_design.html">App Widget Design
Guidelines</a>.</p>
<p class="note">Keep in mind that since the the AppWidgetProvider is a BroadcastReceiver,
your process is not guaranteed to keep running after the callback methods return. See
<a href="../../../guide/topics/fundamentals.html#broadlife">Application Fundamentals &gt;
Broadcast Receiver Lifecycle</a> for more information.
<p>Creating the App Widget layout is simple if you're
familiar with <a href="{@docRoot}guide/topics/ui/declaring-layout.html">Declaring Layout in XML</a>.
However, you must be aware that App Widget layouts are based on {@link android.widget.RemoteViews},
which do not support every kind of layout or view widget.</p>
<p>A RemoteViews object (and, consequently, an App Widget) can support the
following layout classes:</p>
<ul class="nolist">
<li>{@link android.widget.FrameLayout}</li>
<li>{@link android.widget.LinearLayout}</li>
<li>{@link android.widget.RelativeLayout}</li>
</ul>
<p>And the following widget classes:</p>
<ul class="nolist">
<li>{@link android.widget.AnalogClock}</li>
<li>{@link android.widget.Button}</li>
<li>{@link android.widget.Chronometer}</li>
<li>{@link android.widget.ImageButton}</li>
<li>{@link android.widget.ImageView}</li>
<li>{@link android.widget.ProgressBar}</li>
<li>{@link android.widget.TextView}</li>
</ul>
<p>Descendants of these classes are not supported.</p>
<h2 id="AppWidgetProvider">Using the AppWidgetProvider Class</h2>
<h3 id="provider_configuration">AppWidget Configuration UI</h3>
<div class="sidebox-wrapper">
<div class="sidebox-inner">
<p>You must declare your AppWidgetProvider class implementation as a broadcast receiver
using the <code>&lt;receiver></code> element in the AndroidManifest (see
<a href="#Manifest">Declaring an App Widget in the Manifest</a> above).</p>
</div>
</div>
<p>
Widget hosts have the ability to start a configuration activity when a widget is instantiated.
The activity should be declared as normal in AndroidManifest.xml, and it should be listed in
the AppWidgetProviderInfo XML file in the <code>android:configure</code> attribute.
<p>The {@link android.appwidget.AppWidgetProvider} class extends BroadcastReceiver as a convenience
class to handle the App Widget broadcasts. The AppWidgetProvider receives only the event broadcasts that
are relevant to the App Widget, such as when the App Widget is updated, deleted, enabled, and disabled.
When these broadcast events occur, the AppWidgetProvider receives the following method calls:</p>
<p>The activity you specified will be launched with the {@link
android.appwidget.AppWidgetManager#ACTION_APPWIDGET_CONFIGURE} action. See the documentation for that
action for more info.
<dl>
<dt>{@link android.appwidget.AppWidgetProvider#onUpdate(Context,AppWidgetManager,int[])}</dt>
<dd>This is called to update the App Widget at intervals defined by the <code>updatePeriodMillis</code>
attribute in the AppWidgetProviderInfo (see <a href="#MetaData">Adding the
AppWidgetProviderInfo Metadata</a> above). This method is also called
when the user adds the App Widget, so it should perform the essential setup,
such as define event handlers for Views and start a temporary
{@link android.app.Service}, if necessary. However, if you have declared a configuration
Activity, <strong>this method is not called</strong> when the user adds the App Widget,
but is called for the subsequent updates. It is the responsibility of the
configuration Activity to perform the first update when configuration is done.
(See <a href="#Configuring">Creating an App Widget Configuration Activity</a> below.)</dd>
<dt>{@link android.appwidget.AppWidgetProvider#onDeleted(Context,int[])}</dt>
<dd>This is called every time an App Widget is deleted from the App Widget host.</dd>
<dt>{@link android.appwidget.AppWidgetProvider#onEnabled(Context)}</dt>
<dd>This is called when an instance the App Widget is created for the first time. For example, if the user
adds two instances of your App Widget, this is only called the first time.
If you need to open a new database or perform other setup that only needs to occur once
for all App Widget instances, then this is a good place to do it.</dd>
<dt>{@link android.appwidget.AppWidgetProvider#onDisabled(Context)}</dt>
<dd>This is called when the last instance of your App Widget is deleted from the App Widget host.
This is where you should clean up any work done in
{@link android.appwidget.AppWidgetProvider#onEnabled(Context)},
such as delete a temporary database.</dd>
<dt>{@link android.appwidget.AppWidgetProvider#onReceive(Context,Intent)}</dt>
<dd>This is called for every broadcast and before each of the above callback methods.
You normally don't need to implement this method because the default AppWidgetProvider
implementation filters all App Widget broadcasts and calls the above
methods as appropriate.</dd>
</dl>
<p>See the <code>src/com/example/android/apis/appwidget/ExampleAppWidgetConfigure.java</code>
sample class in ApiDemos for an example.
<p class="warning"><strong>Note:</strong> In Android 1.5, there is a known issue in which the
<code>onDeleted()</code> method will not be called when it should be. To work around this issue,
you can implement {@link android.appwidget.AppWidgetProvider#onReceive(Context,Intent)
onReceive()} as described in this
<a href="http://groups.google.com/group/android-developers/msg/e405ca19df2170e2">Group post</a>
to receive the <code>onDeleted()</code> callback.
</p>
<p>The most important AppWidgetProvider callback is
{@link android.appwidget.AppWidgetProvider#onUpdate(Context,AppWidgetManager,int[])
onUpdated()} because it is called when each App Widget is added to a host (unless you use
a configuration Activity). If your App Widget accepts any
user interaction events, then you need to register the event handlers in this callback.
If your App Widget doesn't create temporary
files or databases, or perform other work that requires clean-up, then
{@link android.appwidget.AppWidgetProvider#onUpdate(Context,AppWidgetManager,int[])
onUpdated()} may be the only callback method you need to define. For example, if you want an App Widget
with a button that launches an Activity when clicked, you could use the following
implementation of AppWidgetProvider:</p>
<pre>
public class ExampleAppWidgetProvider extends AppWidgetProvider {
public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
final int N = appWidgetIds.length;
// Perform this loop procedure for each App Widget that belongs to this provider
for (int i=0; i&lt;N; i++) {
int appWidgetId = appWidgetIds[i];
// Create an Intent to launch ExampleActivity
Intent intent = new Intent(context, ExampleActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent, 0);
// Get the layout for the App Widget and attach an on-click listener to the button
RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.appwidget_provider_layout);
views.setOnClickPendingIntent(R.id.button, pendingIntent);
// Tell the AppWidgetManager to perform an update on the current App Widget
appWidgetManager.updateAppWidget(appWidgetId, views);
}
}
}
</pre>
<p>This AppWidgetProvider defines only the
{@link android.appwidget.AppWidgetProvider#onUpdate(Context,AppWidgetManager,int[])
onUpdated()} method for the purpose
of defining a {@link android.app.PendingIntent} that launches an {@link android.app.Activity}
and attaching it to the App Widget's button
with {@link android.widget.RemoteViews#setOnClickPendingIntent(int,PendingIntent)}.
Notice that it includes a loop that iterates through each entry in <code>appWidgetIds</code>, which
is an array of IDs that identify each App Widget created by this provider.
In this way, if the user creates more than one instance of the App Widget, then they are
all updated simultaneously. However, only one <code>updatePeriodMillis</code> schedule will be
managed for all instances of the App Widget. For example, if the update schedule is defined
to be every two hours, and a second instance
of the App Widget is added one hour after the first one, then they will both be updated
on the period defined by the first one and the second update period will be ignored
(they'll both be updated every two hours, not every hour).</p>
<p class="note"><strong>Note:</strong> Because the AppWidgetProvider is a BroadcastReceiver,
your process is not guaranteed to keep running after the callback methods return (see
<a href="{@docRoot}guide/topics/fundamentals.html#broadlife">Application Fundamentals &gt;
Broadcast Receiver Lifecycle</a> for more information). If your App Widget setup process can take several
seconds (perhaps while performing web requests) and you require that your process continues,
consider starting a {@link android.app.Service}
in the {@link android.appwidget.AppWidgetProvider#onUpdate(Context,AppWidgetManager,int[])
onUpdated()} method. From within the Service, you can perform your own updates to the App Widget
without worrying about the AppWidgetProvider closing down due to an
<a href="{@docRoot}guide/practices/design/responsiveness.html">Application Not Responding</a>
(ANR) error. See the
<a href="http://code.google.com/p/wiktionary-android/source/browse/trunk/Wiktionary/src/com/example/android/wiktionary/WordWidget.java">Wiktionary
sample's AppWidgetProvider</a> for an example of an App Widget running a {@link android.app.Service}.</p>
<p>Also see the <a
href="{@docRoot}guide/samples/ApiDemos/src/com/example/android/apis/appwidget/ExampleAppWidgetProvider.html">
ExampleAppWidgetProvider.java</a> sample class.</p>
<h3 id="provider_broadcasts">AppWidget Broadcast Intents</h3>
<h3 id="ProviderBroadcasts">Receiving App Widget broadcast Intents</h3>
<p>{@link android.appwidget.AppWidgetProvider} is just a convenience class. If you would like
to receive the widget broadcasts directly, you can. The four intents you need to care about are:
to receive the App Widget broadcasts directly, you can implement your own
{@link android.content.BroadcastReceiver} or override the
{@link android.appwidget.AppWidgetProvider#onReceive(Context,Intent)} callback.
The four Intents you need to care about are:</p>
<ul>
<li>{@link android.appwidget.AppWidgetManager#ACTION_APPWIDGET_UPDATE}</li>
<li>{@link android.appwidget.AppWidgetManager#ACTION_APPWIDGET_DELETED}</li>
@@ -138,17 +345,119 @@ to receive the widget broadcasts directly, you can. The four intents you need t
<li>{@link android.appwidget.AppWidgetManager#ACTION_APPWIDGET_DISABLED}</li>
</ul>
<p>By way of example, the implementation of
{@link android.appwidget.AppWidgetProvider#onReceive} is quite simple:</p>
{@sample frameworks/base/core/java/android/appwidget/AppWidgetProvider.java onReceive}
<h2 id="Hosts">AppWidget Hosts</h2>
<h2 id="Configuring">Creating an App Widget Configuration Activity</h2>
<p>If you would like the user to configure settings when he or she adds a new App Widget,
you can create an App Widget configuration Activity. This {@link android.app.Activity}
will be automatically launched by the App Widget host and allows the user to configure
available settings for the App Widget at create-time, such as the App Widget color, size,
update period or other functionality settings.</p>
<p>The configuration Activity should be declared as a normal Activity in the Android manifest file.
However, it will be launched by the App Widget host with the {@link
android.appwidget.AppWidgetManager#ACTION_APPWIDGET_CONFIGURE ACTION_APPWIDGET_CONFIGURE} action,
so the Activity needs to accept this Intent. For example:</p>
<pre>
&lt;activity android:name=".ExampleAppWidgetConfigure">
&lt;intent-filter>
&lt;action android:name="android.appwidget.action.APPWIDGET_CONFIGURE" />
&lt;/intent-filter>
&lt;/activity>
</pre>
<p>Also, the Activity must be declared in the AppWidgetProviderInfo XML file, with the
<code>android:configure</code> attribute (see <a href="#MetaData">Adding
the AppWidgetProvierInfo Metadata</a> above). For example, the configuration Activity
can be declared like this:</p>
<pre>
&lt;appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
...
android:configure="com.example.android.ExampleAppWidgetConfigure"
... >
&lt;/appwidget-provider>
</pre>
<p>Notice that the Activity is declared with a fully-qualified namespace, because
it will be referenced from outside your package scope.</p>
<p>That's all you need to get started with a configuration Activity. Now all you need is the actual
Activity. There are, however, two important things to remember when you implement the Activity:</p>
<ul>
<li>The App Widget host calls the configuration Activity and the configuration Activity should always
return a result. The result should include the App Widget ID
passed by the Intent that launched the Activity (saved in the Intent extras as
{@link android.appwidget.AppWidgetManager#EXTRA_APPWIDGET_ID}).</li>
<li>The {@link android.appwidget.AppWidgetProvider#onUpdate(Context,AppWidgetManager,int[])
onUpdate()} method <strong>will not be called</strong> when the App Widget is created
(the system will not send the ACTION_APPWIDGET_UPDATE broadcast when a configuration Activity
is launched). It is the responsibility of the configuration Activity to request an update from the
AppWidgetManager when the App Widget is first created. However,
{@link android.appwidget.AppWidgetProvider#onUpdate(Context,AppWidgetManager,int[])
onUpdate()} will be called for subsequent updates&mdash;it is only skipped the first time.</li>
</ul>
<p>See the code snippets in the following section for an example of how to return a result
from the configuration and update the App Widget.</p>
<h3 id="UpdatingFromTheConfiguration">Updating the App Widget from the configuration Activity</h3>
<p>When an App Widget uses a configuration Activity, it is the responsibility of the Activity
to update the App Widget when configuration is complete.
You can do so by requesting an update directly from the
{@link android.appwidget.AppWidgetManager}.</p>
<p>Here's a summary of the procedure to properly update the App Widget and close
the configuration Activity:</p>
<ol>
<li>First, get the App Widget ID from the Intent that launched the Activity:
<pre>
Intent intent = getIntent();
Bundle extras = intent.getExtras();
if (extras != null) {
mAppWidgetId = extras.getInt(
AppWidgetManager.EXTRA_APPWIDGET_ID,
AppWidgetManager.INVALID_APPWIDGET_ID);
}
</pre>
</li>
<li>Perform your App Widget configuration.</li>
<li>When the configuration is complete, get an instance of the AppWidgetManager by calling
{@link android.appwidget.AppWidgetManager#getInstance(Context)}:
<pre>
AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context);
</pre>
</li>
<li>Update the App Widget with a {@link android.widget.RemoteViews} layout by calling
{@link android.appwidget.AppWidgetManager#updateAppWidget(int,RemoteViews)}:
<pre>
RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.example_appwidget);
appWidgetManager.updateAppWidget(mAppWidgetId, views);
</pre>
</li>
<li>Finally, create the return Intent, set it with the Activity result, and finish the Activity:</li>
<pre>
Intent resultValue = new Intent();
resultValue.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, mAppWidgetId);
setResult(RESULT_OK, resultValue);
finish();
</pre>
</li>
</ol>
<p class="note"><strong>Tip:</strong> When your configuration Activity first opens, set
the Activity result to RESULT_CANCELED. This way, if the user backs-out of the Activity before
reaching the end, the App Widget host is notified that the configuration was cancelled and the
App Widget will not be added.</p>
<p>See the <a
href="{@docRoot}guide/samples/ApiDemos/src/com/example/android/apis/appwidget/ExampleAppWidgetConfigure.html">
ExampleAppWidgetConfigure.java</a> sample class in ApiDemos for an example.</p>
<p>Widget hosts are the containers in which widgets can be placed. Most of the look and feel
details are left up to the widget hosts. For example, the home screen has one way of viewing
widgets, but the lock screen could also contain widgets, and it would have a different way of
adding, removing and otherwise managing widgets.</p>
<p>For more information on implementing your own widget host, see the
{@link android.appwidget.AppWidgetHost AppWidgetHost} class.</p>

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