+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 +
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 +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.
-This document describes how to publish an App Widget using an App Widget provider.
+This document describes how to publish an App Widget using an App Widget +provider.
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 +
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.
The following sections describe how to setup each of these components.
@@ -85,7 +113,8 @@ to modify App Widget settings at create-time.First, declare the {@link android.appwidget.AppWidgetProvider} class in your application's +
First, declare the {@link android.appwidget.AppWidgetProvider} class in your
+application's
AndroidManifest.xml file. For example:
@@ -98,24 +127,32 @@ to modify App Widget settings at create-time. </receiver>-
The <receiver> element requires the android:name
+
The <receiver> element requires the
+android:name
attribute, which specifies the {@link android.appwidget.AppWidgetProvider} used
by the App Widget.
The <intent-filter> element must include an <action>
+
The <intent-filter> element must include an
+<action>
element with the android:name 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.
The <meta-data> element specifies the
{@link android.appwidget.AppWidgetProviderInfo} resource and requires the
following attributes:
android:name - Specifies the metadata name. Use android.appwidget.provider
- to identify the data as the {@link android.appwidget.AppWidgetProviderInfo} descriptor.android:resource - Specifies the {@link android.appwidget.AppWidgetProviderInfo}
+ android:name - Specifies the metadata name. Use
+android.appwidget.provider
+ to identify the data as the {@link android.appwidget.AppWidgetProviderInfo}
+descriptor.android:resource - Specifies the {@link
+android.appwidget.AppWidgetProviderInfo}
resource location.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.
+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
-<appwidget-provider> element and save it in the project's res/xml/
+<appwidget-provider> element and save it in the project's
+res/xml/
folder.
For example:
@@ -136,71 +176,131 @@ folder. android:minWidth="294dp" android:minHeight="72dp" android:updatePeriodMillis="86400000" + android:previewImage="@drawable/preview" android:initialLayout="@layout/example_appwidget" - android:configure="com.example.android.ExampleAppWidgetConfigure" > + android:configure="com.example.android.ExampleAppWidgetConfigure" + android:resizeMode="horizontal|vertical"> </appwidget-provider>Here's a summary of the <appwidget-provider> attributes:
minWidth and minHeight attributes specify the minimum
- area required by the App Widget's layout.
- 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 +
minWidth and minHeight
+attributes specify the minimum
+ area required by the App Widget's layout.
+ 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 up to the nearest cell size. - (See the App Widget Design + (See the App Widget +Design Guidelines for more information on the Home screen cell sizes.)
-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 - and 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 +
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
+ and 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:
(number of cells * 74) - 2
- Following this formula, you should use 72 dp for a height of one cell, 294 dp and for a width of four cells.
Note: To make your app widget portable across +devices, your app widget's minimum size should never be larger than 4 x 4 cells. +See the App +Widget Design Guidelines for more discussion of Home screen cell sizes.
updatePeriodMillis 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—perhaps no more than once an hour to
- conserve the battery. You might also allow the user to adjust the frequency in a
- configuration—some people might want a stock ticker to update every 15 minutes, or maybe
- only four times a day.
- Note: If the device is asleep when it is time for an update
- (as defined by updatePeriodMillis), then the device will wake up in order
- to perform the update. If you don't update more than once per hour, this probably won't
- cause significant problems for the battery life. If, however, you need to update more
- frequently and/or you do not need to update while the device is asleep, then you can instead
- perform updates based on an alarm that will not wake the device. To do so, set an alarm with
- an Intent that your AppWidgetProvider receives, using the {@link android.app.AlarmManager}.
- Set the alarm type to either {@link android.app.AlarmManager#ELAPSED_REALTIME} or
+
updatePeriodMillis 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(android.content.Context,android.appwidget.AppWidgetManager,int[]) onUpdate()}
+callback method. The actual update
+is not guaranteed to occur exactly on time with this value and we suggest
+updating as infrequently as possible—perhaps no more than once an hour to
+conserve the battery. You might also allow the user to adjust the frequency in a
+configuration—some people might want a stock ticker to update every 15
+minutes, or maybe only four times a day.
+ Note: If the device is asleep when it
+is time for an update
+ (as defined by updatePeriodMillis), then the device will
+wake up in order
+ to perform the update. If you don't update more than once per hour, this
+probably won't
+ cause significant problems for the battery life. If, however, you need
+to update more
+ frequently and/or you do not need to update while the device is asleep,
+then you can instead
+ perform updates based on an alarm that will not wake the device. To do
+so, set an alarm with
+ an Intent that your AppWidgetProvider receives, using the {@link
+android.app.AlarmManager}.
+ Set the alarm type to either {@link
+android.app.AlarmManager#ELAPSED_REALTIME} or
{@link android.app.AlarmManager#RTC}, which will only
- deliver the alarm when the device is awake. Then set updatePeriodMillis to
+ deliver the alarm when the device is awake. Then set
+updatePeriodMillis to
zero ("0").
initialLayout attribute points to the layout resource that defines the
+ initialLayout attribute points to the layout resource
+that defines the
App Widget layout.configure 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 Creating an App Widget Configuration Activity below).configure 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 Creating an App Widget Configuration
+Activity below).previewImage attribute specifies a preview of what the
+app widget will look like after it's configured, which the user sees when
+selecting the app widget. If not supplied, the user instead sees your
+application's launcher icon. This field corresponds to the
+android:previewImage attribute in the <receiver>
+element in the AndroidManifest.xml file. For more discussion of
+using previewImage, see Setting a Preview
+Image. Introduced in Android 3.0.See the {@link android.appwidget.AppWidgetProviderInfo} class for more information on the +
autoAdvanceViewId attribute specifies the view ID of the
+app widget subview that should be auto-advanced by the widget's host. Introduced in Android 3.0.resizeMode attribute specifies the rules by which a widget
+can be resized. You use this attribute to make homescreen widgets
+resizeable—horizontally, vertically, or on both axes. Users touch-hold a
+widget to show its resize handles, then drag the horizontal and/or vertical
+handles to change the size on the layout grid. Values for the
+resizeMode attribute include "horizontal", "vertical", and "none".
+To declare a widget as resizeable horizontally and vertically, supply the value
+"horizontal|vertical". Introduced in Android 3.1.See the {@link android.appwidget.AppWidgetProviderInfo} class for more
+information on the
attributes accepted by the <appwidget-provider> element.
You must define an initial layout for your App Widget in XML and save it in the project's
- You must define an initial layout for your App Widget in XML and save it in
+the project's
+ Creating the App Widget layout is simple if you're
-familiar with Declaring Layout in XML.
-However, you must be aware that App Widget layouts are based on {@link android.widget.RemoteViews},
+familiar with Declaring Layout in
+XML.
+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. A RemoteViews object (and, consequently, an App Widget) can support the
@@ -221,6 +321,7 @@ following layout classes: Descendants of these classes are not supported.res/layout/ 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
-App Widget Design
+res/layout/ 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
+App Widget
+Design
Guidelines.
You must declare your AppWidgetProvider class implementation as a broadcast receiver +
You must declare your AppWidgetProvider class implementation as a
+broadcast receiver
using the <receiver> element in the AndroidManifest (see
Declaring an App Widget in the Manifest above).
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:
+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:
updatePeriodMillis
+ updatePeriodMillis
attribute in the AppWidgetProviderInfo (see Adding the
AppWidgetProviderInfo Metadata 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, this method is not called when the user adds the App Widget,
+ {@link android.app.Service}, if necessary. However, if you have declared a
+configuration
+ Activity, this method is not called 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 Creating an App Widget Configuration Activity below.)Note: In Android 1.5, there is a known issue in which the
-onDeleted() method will not be called when it should be. To work around this issue,
-you can implement {@link android.appwidget.AppWidgetProvider#onReceive(Context,Intent)
+
Note: In Android 1.5, there is a known issue
+in which the
+onDeleted() 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
-Group post
+
+Group post
to receive the onDeleted() callback.
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 +{@link android.appwidget.AppWidgetProvider#onUpdate(android.content.Context, android.appwidget.AppWidgetManager, int[]) onUpdate()} +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(android.content.Context, android.appwidget.AppWidgetManager, int[]) onUpdate()} +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:
@@ -306,11 +431,12 @@ public class ExampleAppWidgetProvider extends AppWidgetProvider {
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
+ // 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
+ // Tell the AppWidgetManager to perform an update on the current app widget
appWidgetManager.updateAppWidget(appWidgetId, views);
}
}
@@ -318,43 +444,51 @@ public class ExampleAppWidgetProvider extends AppWidgetProvider {
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 appWidgetIds, 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 updatePeriodMillis 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).
appWidgetIds, 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 updatePeriodMillis 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).
-Note: Because {@link android.appwidget.AppWidgetProvider} is an -extension of {@link android.content.BroadcastReceiver}, your process is not guaranteed to keep -running after the callback methods return (see {@link android.content.BroadcastReceiver} for -information about the broadcast lifecycle). 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 -Application Not Responding -(ANR) error. See the -Wiktionary -sample's AppWidgetProvider for an example of an App Widget running a {@link android.app.Service}.
+Note: Because {@link +android.appwidget.AppWidgetProvider} is an extension of {@link +android.content.BroadcastReceiver}, your process is not guaranteed to keep +running after the callback methods return (see {@link +android.content.BroadcastReceiver} for information about the broadcast +lifecycle). 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[]) onUpdate()} +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 Application +Not Responding (ANR) error. See the Wiktionary sample's +AppWidgetProvider for an example of an App Widget running a {@link +android.app.Service}.
Also see the +href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/ +appwidget/ExampleAppWidgetProvider.html"> ExampleAppWidgetProvider.java sample class.
{@link android.appwidget.AppWidgetProvider} is just a convenience class. If you would like +
{@link android.appwidget.AppWidgetProvider} is just a convenience class. If +you would like 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. @@ -370,28 +504,36 @@ The four Intents you need to care about are:
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, +
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.
-The configuration Activity should be declared as a normal Activity in the Android manifest file. +
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, +android.appwidget.AppWidgetManager#ACTION_APPWIDGET_CONFIGURE +ACTION_APPWIDGET_CONFIGURE} action, so the Activity needs to accept this Intent. For example:
<activity android:name=".ExampleAppWidgetConfigure">
<intent-filter>
- <action android:name="android.appwidget.action.APPWIDGET_CONFIGURE" />
+ <action android:name="android.appwidget.action.APPWIDGET_CONFIGURE"/>
</intent-filter>
</activity>
-Also, the Activity must be declared in the AppWidgetProviderInfo XML file, with the +
Also, the Activity must be declared in the AppWidgetProviderInfo XML file,
+with the
android:configure attribute (see Adding
-the AppWidgetProviderInfo Metadata above). For example, the configuration Activity
+the AppWidgetProviderInfo Metadata above). For example, the configuration
+Activity
can be declared like this:
@@ -402,32 +544,45 @@ can be declared like this: </appwidget-provider>-
Notice that the Activity is declared with a fully-qualified namespace, because +
Notice that the Activity is declared with a fully-qualified namespace, +because it will be referenced from outside your package scope.
-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:
+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:
See the code snippets in the following section for an example of how to return a result +
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.
-When an App Widget uses a configuration Activity, it is the responsibility of the Activity +
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}.
@@ -448,20 +603,24 @@ if (extras != null) {AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context);
-RemoteViews views = new RemoteViews(context.getPackageName(), R.layout.example_appwidget); +RemoteViews views = new RemoteViews(context.getPackageName(), +R.layout.example_appwidget); appWidgetManager.updateAppWidget(mAppWidgetId, views);
Intent resultValue = new Intent(); resultValue.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, mAppWidgetId); @@ -471,14 +630,657 @@ finish(); -Tip: 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 +
Tip: 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.
See the +href="{@docRoot}resources/samples/ApiDemos/src/com/example/android/apis/ +appwidget/ExampleAppWidgetConfigure.html"> ExampleAppWidgetConfigure.java sample class in ApiDemos for an example.
+Setting a Preview Image
+ +Android 3.0 introduces the {@link + + +android.appwidget.AppWidgetProviderInfo#previewImage} field, which specifies a +preview of what the app widget looks like. This preview is shown to the user from the +widget picker. If this field is not supplied, the app widget's icon is used for +the preview.
+ +This is how you specify this setting in XML:
+ +<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android" + ... + android:previewImage="@drawable/preview"> +</appwidget-provider>+ +To help create a preview image for your app widget (to specify in the {@link +android.appwidget.AppWidgetProviderInfo#previewImage} field), the Android +emulator includes an application called "Widget Preview." To create a +preview image, launch this application, select the app widget for your +application and set it up how you'd like your preview image to appear, then save +it and place it in your application's drawable resources.
+ +Using App Widgets with Collections
+ +Android 3.0 introduces App Widgets with collections. These kinds of App +Widgets use the {@link android.widget.RemoteViewsService} to display collections +that are backed by remote data, such as from a content +provider. The data provided by the {@link android.widget.RemoteViewsService} +is presented in the App Widget using one of the following view types, which +we’ll refer to as “collection views:”
+ +
As stated above, these collection views display collections backed by remote +data. This means that they use an {@link android.widget.Adapter} to bind their +user interface to their data. An {@link android.widget.Adapter} binds individual +items from a set of data into individual {@link android.view.View} objects. +Because these collection views are backed by adapters, the Android framework +must include extra architecture to support their use in app widgets. In the +context of an app widget, the {@link android.widget.Adapter} is replaced by a +{@link android.widget.RemoteViewsService.RemoteViewsFactory RemoteViewsFactory}, +which is simply a thin wrapper around the {@link android.widget.Adapter} +interface. + When +requested for a specific item in the collection, the {@link +android.widget.RemoteViewsService.RemoteViewsFactory RemoteViewsFactory} creates +and returns the item for the collection as a {@link android.widget.RemoteViews} +object. +In order to include a collection view in your app widget, you +must implement {@link android.widget.RemoteViewsService} and {@link +android.widget.RemoteViewsService.RemoteViewsFactory RemoteViewsFactory}.
+ +{@link android.widget.RemoteViewsService} is a service that allows a remote +adapter to request {@link +android.widget.RemoteViews} objects. {@link +android.widget.RemoteViewsService.RemoteViewsFactory RemoteViewsFactory} is an +interface for an adapter between a collection view (such as {@link +android.widget.ListView}, {@link android.widget.GridView}, and so on) and the +underlying data for that view. From the StackView Widget +sample, here is an example of the boilerplate code you use to implement +this service and interface: +
+ +
+public class StackWidgetService extends RemoteViewsService {
+ @Override
+ public RemoteViewsFactory onGetViewFactory(Intent intent) {
+ return new StackRemoteViewsFactory(this.getApplicationContext(), intent);
+ }
+}
+
+class StackRemoteViewsFactory implements RemoteViewsService.RemoteViewsFactory {
+
+//... include adapter-like methods here. See the StackView Widget sample.
+
+}
+
+
+The code excerpts in this section are drawn from the StackView Widget +sample:
+ +
+
+
This sample consists of a stack of 10 views, which display the values
+"0!" through "9!" The sample
+app widget has these primary behaviors:
android:autoAdvanceViewId="@id/stack_view" in the
+res/xml/stackwidgetinfo.xml file. This setting applies to the view
+ID,
+which in this case is the view ID of the stack view.To implement an App Widget with collections, you follow the same basic steps +you would use to implement any app widget. The following sections describe the +additional steps you need to perform to implement an App Widget with +collections.
+ +In addition to the requirements listed in Declaring an +App Widget in the Manifest, to make it possible for App Widgets with +collections to bind to your {@link android.widget.RemoteViewsService}, you must +declare the service in your manifest file with the permission {@link +android.Manifest.permission#BIND_REMOTEVIEWS}. This prevents other applications +from freely accessing your app widget's data. For example, when creating an App +Widget that uses {@link android.widget.RemoteViewsService} to populate a +collection view, the manifest entry may look like this:
+ +<service android:name="MyWidgetService" +... +android:permission="android.permission.BIND_REMOTEVIEWS" />+ +
The line android:name="MyWidgetService"
+refers to your subclass of {@link android.widget.RemoteViewsService}.
The main requirement for your app widget layout XML file is that it
+include one of the collection views: {@link android.widget.ListView},
+{@link android.widget.GridView}, {@link android.widget.StackView}, or
+{@link android.widget.AdapterViewFlipper}. Here is the
+widget_layout.xml for
+the StackView
+Widget sample:
<?xml version="1.0" encoding="utf-8"?> + +<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" + android:layout_width="match_parent" + android:layout_height="match_parent"> + <StackView xmlns:android="http://schemas.android.com/apk/res/android" + android:id="@+id/stack_view" + android:layout_width="match_parent" + android:layout_height="match_parent" + android:gravity="center" + android:loopViews="true" /> + <TextView xmlns:android="http://schemas.android.com/apk/res/android" + android:id="@+id/empty_view" + android:layout_width="match_parent" + android:layout_height="match_parent" + android:gravity="center" + android:background="@drawable/widget_item_background" + android:textColor="#ffffff" + android:textStyle="bold" + android:text="@string/empty_view_text" + android:textSize="20sp" /> +</FrameLayout>+ +
Note that empty views must be siblings of the collection view for which the +empty view represents empty state.
+ +In addition to the layout file for your entire app widget, you must create
+another layout file that defines the layout for each item in the collection (for
+example, a layout for each book in a collection of books). For example, the StackView Widget
+sample only has one layout file, widget_item.xml, since all
+items use the same layout. But the
+WeatherListWidget sample has two layout files:
+dark_widget_item.xml and light_widget_item.xml.
As with a regular app widget, the bulk of your code in your {@link +android.appwidget.AppWidgetProvider} subclass typically goes in {@link +android.appwidget.AppWidgetProvider#onUpdate(android.content.Context, +android.appwidget.AppWidgetManager, int[]) onUpdate()}. The major difference in +your implementation for {@link +android.appwidget.AppWidgetProvider#onUpdate(android.content.Context, +android.appwidget.AppWidgetManager, int[]) onUpdate()} when creating an app +widget with collections is that you must call {@link +android.widget.RemoteViews#setRemoteAdapter setRemoteAdapter()}. This tells the +collection view where to get its data. The {@link +android.widget.RemoteViewsService} can then return your implementation of {@link +android.widget.RemoteViewsService.RemoteViewsFactory RemoteViewsFactory}, and +the widget can serve up the appropriate data. When you call this method, you +must pass an intent that points to your implementation of {@link +android.widget.RemoteViewsService} and the App Widget ID that specifies the app +widget to update.
+ + +For example, here's how the StackView Widget sample implements the {@link +android.appwidget.AppWidgetProvider#onUpdate(android.content.Context, +android.appwidget.AppWidgetManager, int[]) onUpdate()} callback method to set +the {@link +android.widget.RemoteViewsService} as the remote adapter for the app widget +collection:
+ +public void onUpdate(Context context, AppWidgetManager appWidgetManager,
+int[] appWidgetIds) {
+ // update each of the app widgets with the remote adapter
+ for (int i = 0; i < appWidgetIds.length; ++i) {
+
+ // Set up the intent that starts the StackViewService, which will
+ // provide the views for this collection.
+ Intent intent = new Intent(context, StackWidgetService.class);
+ // Add the app widget ID to the intent extras.
+ intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetIds[i]);
+ intent.setData(Uri.parse(intent.toUri(Intent.URI_INTENT_SCHEME)));
+ // Instantiate the RemoteViews object for the App Widget layout.
+ RemoteViews rv = new RemoteViews(context.getPackageName(), R.layout.widget_layout);
+ // Set up the RemoteViews object to use a RemoteViews adapter.
+ // This adapter connects
+ // to a RemoteViewsService through the specified intent.
+ // This is how you populate the data.
+ rv.setRemoteAdapter(appWidgetIds[i], R.id.stack_view, intent);
+
+ // The empty view is displayed when the collection has no items.
+ // It should be in the same layout used to instantiate the RemoteViews
+ // object above.
+ rv.setEmptyView(R.id.stack_view, R.id.empty_view);
+
+ //
+ // Do additional processing specific to this app widget...
+ //
+
+ appWidgetManager.updateAppWidget(appWidgetIds[i], rv);
+ }
+ super.onUpdate(context, appWidgetManager, appWidgetIds);
+}
+
+You can’t rely on a single instance of your service, or any data it +contains, to persist. You should therefore not store any data in your {@link +android.widget.RemoteViewsService} (unless it is static). If you want your +app widget’s data to persist, the best approach is to use a {@link +android.content.ContentProvider} whose data persists beyond the process +lifecycle.
As described above, your {@link android.widget.RemoteViewsService} subclass +provides the {@link android.widget.RemoteViewsService.RemoteViewsFactory +RemoteViewsFactory} used to populate the remote collection view.
+ +Specifically, you need to +perform these steps:
+ +The primary contents of the {@link android.widget.RemoteViewsService} +implementation is its {@link +android.widget.RemoteViewsService.RemoteViewsFactory RemoteViewsFactory}, +described below.
+ +Your custom class that implements the {@link
+android.widget.RemoteViewsService.RemoteViewsFactory RemoteViewsFactory}
+interface provides the app widget with the data for the items in its collection.
+To
+do this, it combines your app widget item XML layout file with a source of data.
+This source of data could be anything from a database to a simple array. In the
+StackView Widget
+sample, the data source is an array of WidgetItems. The {@link
+android.widget.RemoteViewsService.RemoteViewsFactory RemoteViewsFactory}
+functions as an adapter to glue the data to the remote collection view.
The two most important methods you need to implement for your + +{@link android.widget.RemoteViewsService.RemoteViewsFactory RemoteViewsFactory} +subclass are +{@link android.widget.RemoteViewsService.RemoteViewsFactory#onCreate() +onCreate()} and +{@link android.widget.RemoteViewsService.RemoteViewsFactory#getViewAt(int) +getViewAt()} +.
+ +The system calls {@link
+android.widget.RemoteViewsService.RemoteViewsFactory#onCreate() onCreate()} when
+creating your factory for the first time. This is where you set up any
+connections and/or cursors to your data source. For example, the StackView Widget
+sample uses {@link
+android.widget.RemoteViewsService.RemoteViewsFactory#onCreate() onCreate()} to
+initialize an array of WidgetItem objects. When your app widget is
+active, the system accesses these objects using their index position in the
+array and the text they contain is displayed
Here is an excerpt from the the StackView Widget +sample's +{@link android.widget.RemoteViewsService.RemoteViewsFactory +RemoteViewsFactory} implementation that shows portions of the {@link +android.widget.RemoteViewsService.RemoteViewsFactory#onCreate() onCreate()} +method:
+ +class StackRemoteViewsFactory implements
+RemoteViewsService.RemoteViewsFactory {
+ private static final int mCount = 10;
+ private List<WidgetItem> mWidgetItems = new ArrayList<WidgetItem>();
+ private Context mContext;
+ private int mAppWidgetId;
+
+ public StackRemoteViewsFactory(Context context, Intent intent) {
+ mContext = context;
+ mAppWidgetId = intent.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID,
+ AppWidgetManager.INVALID_APPWIDGET_ID);
+ }
+
+ public void onCreate() {
+ // In onCreate() you setup any connections / cursors to your data source. Heavy lifting,
+ // for example downloading or creating content etc, should be deferred to onDataSetChanged()
+ // or getViewAt(). Taking more than 20 seconds in this call will result in an ANR.
+ for (int i = 0; i < mCount; i++) {
+ mWidgetItems.add(new WidgetItem(i + "!"));
+ }
+ ...
+ }
+...
+
+The {@link android.widget.RemoteViewsService.RemoteViewsFactory
+RemoteViewsFactory} method {@link
+android.widget.RemoteViewsService.RemoteViewsFactory#getViewAt(int) getViewAt()}
+returns a {@link android.widget.RemoteViews} object corresponding to the data at
+the specified position in the data set. Here is an excerpt from
+the
+StackView Widget sample's {@link
+android.widget.RemoteViewsService.RemoteViewsFactory RemoteViewsFactory}
+implementation:
public RemoteViews getViewAt(int position) {
+
+ // Construct a remote views item based on the app widget item XML file,
+ // and set the text based on the position.
+ RemoteViews rv = new RemoteViews(mContext.getPackageName(), R.layout.widget_item);
+ rv.setTextViewText(R.id.widget_item, mWidgetItems.get(position).text);
+
+ ...
+ // Return the remote views object.
+ return rv;
+}
+
+The above sections show you how to bind your data to your app widget +collection. But what if you want to add dynamic behavior to the individual items +in your collection view?
+ +As described in Using the AppWidgetProvider +Class, you normally use {@link +android.widget.RemoteViews#setOnClickPendingIntent(int, +android.app.PendingIntent) setOnClickPendingIntent()} to set an object's click +behavior—such as to cause a button to launch an {@link +android.app.Activity}. But this approach is not allowed for child views in an +individual collection item (to clarify, you could use {@link +android.widget.RemoteViews#setOnClickPendingIntent(int, +android.app.PendingIntent) setOnClickPendingIntent()} to set up a global button +in the Gmail app widget that launches the app, for example, but not on the +individual list items). Instead, to add click behavior to individual items in a +collection, you use {@link +android.widget.RemoteViews#setOnClickFillInIntent(int, android.content.Intent) +setOnClickFillInIntent()}. This entails setting up up a pending intent template +for your collection view, and then setting a fill-in intent on each item in the +collection via your {@link android.widget.RemoteViewsService.RemoteViewsFactory +RemoteViewsFactory}.
+This section uses the StackView Widget +sample to describe how to add behavior to individual items. In the StackView Widget +sample, if the user touches the top view, the app widget displays the {@link +android.widget.Toast} message "Touched view n," where +n is the index (position) of the touched view. This is how it +works:
+ +StackWidgetProvider (an {@link
+android.appwidget.AppWidgetProvider} subclass) creates a pending intent that has
+a custom action called TOAST_ACTION.TOAST_ACTION.StackWidgetProvider's
+{@link android.appwidget.AppWidgetProvider#onReceive(android.content.Context,
+android.content.Intent) onReceive()} method, and the app widget displays the
+{@link
+android.widget.Toast} message for the touched view. The data for the collection
+items is provided by the {@link
+android.widget.RemoteViewsService.RemoteViewsFactory RemoteViewsFactory}, via
+the {@link android.widget.RemoteViewsService}.Note: The StackView Widget +sample uses a broadcast, but typically an app widget would simply launch an +activity in a scenario like this one.
+ +The StackWidgetProvider ({@link
+android.appwidget.AppWidgetProvider} subclass) sets up a pending intent.
+Individuals items of a collection cannot set up their own pending intents.
+Instead, the collection as a whole sets up a pending intent template, and the
+individual items set a fill-in intent to create unique behavior on an
+item-by-item
+basis.
This class also receives the broadcast that is sent when the user touches a
+view. It processes this event in its {@link
+android.appwidget.AppWidgetProvider#onReceive(android.content.Context,
+android.content.Intent) onReceive()} method. If the intent's action is
+TOAST_ACTION, the app widget displays a {@link
+android.widget.Toast}
+message for the current view.
public class StackWidgetProvider extends AppWidgetProvider {
+ public static final String TOAST_ACTION = "com.example.android.stackwidget.TOAST_ACTION";
+ public static final String EXTRA_ITEM = "com.example.android.stackwidget.EXTRA_ITEM";
+
+ ...
+
+ // Called when the BroadcastReceiver receives an Intent broadcast.
+ // Checks to see whether the intent's action is TOAST_ACTION. If it is, the app widget
+ // displays a Toast message for the current item.
+ @Override
+ public void onReceive(Context context, Intent intent) {
+ AppWidgetManager mgr = AppWidgetManager.getInstance(context);
+ if (intent.getAction().equals(TOAST_ACTION)) {
+ int appWidgetId = intent.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID,
+ AppWidgetManager.INVALID_APPWIDGET_ID);
+ int viewIndex = intent.getIntExtra(EXTRA_ITEM, 0);
+ Toast.makeText(context, "Touched view " + viewIndex, Toast.LENGTH_SHORT).show();
+ }
+ super.onReceive(context, intent);
+ }
+
+ @Override
+ public void onUpdate(Context context, AppWidgetManager appWidgetManager, int[] appWidgetIds) {
+ // update each of the app widgets with the remote adapter
+ for (int i = 0; i < appWidgetIds.length; ++i) {
+
+ // Sets up the intent that points to the StackViewService that will
+ // provide the views for this collection.
+ Intent intent = new Intent(context, StackWidgetService.class);
+ intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetIds[i]);
+ // When intents are compared, the extras are ignored, so we need to embed the extras
+ // into the data so that the extras will not be ignored.
+ intent.setData(Uri.parse(intent.toUri(Intent.URI_INTENT_SCHEME)));
+ RemoteViews rv = new RemoteViews(context.getPackageName(), R.layout.widget_layout);
+ rv.setRemoteAdapter(appWidgetIds[i], R.id.stack_view, intent);
+
+ // The empty view is displayed when the collection has no items. It should be a sibling
+ // of the collection view.
+ rv.setEmptyView(R.id.stack_view, R.id.empty_view);
+
+ // This section makes it possible for items to have individualized behavior.
+ // It does this by setting up a pending intent template. Individuals items of a collection
+ // cannot set up their own pending intents. Instead, the collection as a whole sets
+ // up a pending intent template, and the individual items set a fillInIntent
+ // to create unique behavior on an item-by-item basis.
+ Intent toastIntent = new Intent(context, StackWidgetProvider.class);
+ // Set the action for the intent.
+ // When the user touches a particular view, it will have the effect of
+ // broadcasting TOAST_ACTION.
+ toastIntent.setAction(StackWidgetProvider.TOAST_ACTION);
+ toastIntent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetIds[i]);
+ intent.setData(Uri.parse(intent.toUri(Intent.URI_INTENT_SCHEME)));
+ PendingIntent toastPendingIntent = PendingIntent.getBroadcast(context, 0, toastIntent,
+ PendingIntent.FLAG_UPDATE_CURRENT);
+ rv.setPendingIntentTemplate(R.id.stack_view, toastPendingIntent);
+
+ appWidgetManager.updateAppWidget(appWidgetIds[i], rv);
+ }
+ super.onUpdate(context, appWidgetManager, appWidgetIds);
+ }
+}
+
+Your {@link android.widget.RemoteViewsService.RemoteViewsFactory +RemoteViewsFactory} must set a fill-in intent on each item in the collection. +This makes it possible to distinguish the individual on-click action of a given +item. The fill-in intent is then combined with the {@link +android.app.PendingIntent} template in order to determine the final intent that +will be executed when the item is clicked.
+ +
+public class StackWidgetService extends RemoteViewsService {
+ @Override
+ public RemoteViewsFactory onGetViewFactory(Intent intent) {
+ return new StackRemoteViewsFactory(this.getApplicationContext(), intent);
+ }
+}
+
+class StackRemoteViewsFactory implements RemoteViewsService.RemoteViewsFactory {
+ private static final int mCount = 10;
+ private List<WidgetItem> mWidgetItems = new ArrayList<WidgetItem>();
+ private Context mContext;
+ private int mAppWidgetId;
+
+ public StackRemoteViewsFactory(Context context, Intent intent) {
+ mContext = context;
+ mAppWidgetId = intent.getIntExtra(AppWidgetManager.EXTRA_APPWIDGET_ID,
+ AppWidgetManager.INVALID_APPWIDGET_ID);
+ }
+
+ // Initialize the data set.
+ public void onCreate() {
+ // In onCreate() you set up any connections / cursors to your data source. Heavy lifting,
+ // for example downloading or creating content etc, should be deferred to onDataSetChanged()
+ // or getViewAt(). Taking more than 20 seconds in this call will result in an ANR.
+ for (int i = 0; i < mCount; i++) {
+ mWidgetItems.add(new WidgetItem(i + "!"));
+ }
+ ...
+ }
+ ...
+
+ // Given the position (index) of a WidgetItem in the array, use the item's text value in
+ // combination with the app widget item XML file to construct a RemoteViews object.
+ public RemoteViews getViewAt(int position) {
+ // position will always range from 0 to getCount() - 1.
+
+ // Construct a RemoteViews item based on the app widget item XML file, and set the
+ // text based on the position.
+ RemoteViews rv = new RemoteViews(mContext.getPackageName(), R.layout.widget_item);
+ rv.setTextViewText(R.id.widget_item, mWidgetItems.get(position).text);
+
+ // Next, set a fill-intent, which will be used to fill in the pending intent template
+ // that is set on the collection view in StackWidgetProvider.
+ Bundle extras = new Bundle();
+ extras.putInt(StackWidgetProvider.EXTRA_ITEM, position);
+ Intent fillInIntent = new Intent();
+ fillInIntent.putExtras(extras);
+ // Make it possible to distinguish the individual on-click
+ // action of a given item
+ rv.setOnClickFillInIntent(R.id.widget_item, fillInIntent);
+
+ ...
+
+ // Return the RemoteViews object.
+ return rv;
+ }
+ ...
+ }
+
+The following figure illustrates the flow that occurs in an App Widget that +uses +collections when updates occur. It shows how the App Widget code interacts with +the {@link android.widget.RemoteViewsService.RemoteViewsFactory +RemoteViewsFactory}, and how you can trigger updates:
+ +
+
+One feature of App Widgets that use collections is the ability to provide
+users with up-to-date content. For example, consider the Android 3.0 Gmail
+app widget, which provides users with a snapshot of their inbox. To make this
+possible, you need to be able to trigger your {@link
+android.widget.RemoteViewsService.RemoteViewsFactory RemoteViewsFactory} and
+collection view to fetch and display new data. You achieve this with the {@link
+android.appwidget.AppWidgetManager} call {@link
+android.appwidget.AppWidgetManager#notifyAppWidgetViewDataChanged(int, int)
+notifyAppWidgetViewDataChanged()}. This call results in a callback to your
+RemoteViewsFactory’s {@link
+android.widget.RemoteViewsService.RemoteViewsFactory#onDataSetChanged()
+onDataSetChanged()} method, which gives you the opportunity to fetch any new
+data. Note that you can perform
+processing-intensive operations synchronously within the {@link
+android.widget.RemoteViewsService.RemoteViewsFactory#onDataSetChanged()
+onDataSetChanged()} callback. You are guaranteed that this call will be
+completed before the metadata or view data is fetched from the {@link
+android.widget.RemoteViewsService.RemoteViewsFactory RemoteViewsFactory}. In
+addition, you can perform processing-intensive operations within the {@link
+android.widget.RemoteViewsService.RemoteViewsFactory#getViewAt(int) getViewAt()}
+method. If this call takes a long time, the loading view (specified by the
+RemoteViewsFactory’s {@link
+android.widget.RemoteViewsService.RemoteViewsFactory#getLoadingView()} method)
+will be displayed in the corresponding position of the collection view until it
+returns.