App Widgets are miniature application views that can be embedded in other applications (such as the Home screen) and receive periodic updates.Home screen widgets are broadcast receivers which provide interactive components. They are primarily used on the Android home screen. They typically display some kind of data and allow the user to perform actions with them.
Declaring an App Widget in the Manifest
|
1 2 3 4 5 6 7 |
<receiver android:name="ExampleAppWidgetProvider" > <intent-filter> <action android:name="android.appwidget.action.APPWIDGET_UPDATE" /> </intent-filter> <meta-data android:name="android.appwidget.provider" android:resource="@xml/example_appwidget_info" /> </receiver> |
Adding the AppWidgetProviderInfo Metadata
Define the AppWidgetProviderInfo object in an XML resource using a single <appwidget-provider> element and save it in the project’s res/xml/ folder.
|
1 2 3 4 5 6 7 8 9 10 |
<appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android" android:minWidth="40dp" android:minHeight="40dp" android:updatePeriodMillis="86400000" android:previewImage="@drawable/preview" android:initialLayout="@layout/example_appwidget" android:configure="com.example.android.ExampleAppWidgetConfigure" android:resizeMode="horizontal|vertical" android:widgetCategory="home_screen"> </appwidget-provider> |
Create a layout such as the one below, that references a dimension resource for its margins:
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 |
<FrameLayout android:layout_width="match_parent" android:layout_height="match_parent" android:padding="@dimen/widget_margin"> <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" android:background="@drawable/my_widget_background"> … </LinearLayout> </FrameLayout> |
The most important AppWidgetProvider callback is 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 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:
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 |
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<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); } } } |
If you want to be refresh/update widget view on AppWidget make update widget method, you can invoke the method on click event.
|
1 2 3 4 5 6 7 |
public void updateWidget() { AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(getApplicationContext()); int[] appWidgetIds = appWidgetManager.getAppWidgetIds(new ComponentName(this, OpenCartWidget.class)); if (appWidgetIds.length > 0) { new OpenCartWidget().onUpdate(this, appWidgetManager, appWidgetIds); } } |
Hope it will help you to know the basic structure of AppWidget.