AppWidgetProvider使用介绍

一 介绍

AppWidgetProvider是android中提供的用于实现桌面小工具的类，其本质是一个广播，即BroadcastReceiver。下面是类的继承关系。

所以，在实际的使用中，把AppWidgetProvider当成一个BroadcastReceiver就可以了，这样许多功能就很好理解了。

二 开发一个桌面小工具的步骤

1 定义小工具界面：在res/layout/下新建一个xml文件，名为widget.xml，名称和内容可以自定义，看你的小工具要做成什么样子。

 <?xml version="1.0" encoding="utf-8"?>
 <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="fill_parent"
     android:layout_height="fill_parent" >

     <ImageView
         android:id="@+id/imageView1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_alignParentLeft="true"
         android:layout_alignParentTop="true"
         android:src="@drawable/clear_cover" />

 </RelativeLayout>

2 定义小工具配置信息：在res/xml/下新建appwidget_provider_info.xml，名称随意选，添加如下内容

 <?xml version="1.0" encoding="utf-8"?>
 <appwidget-provider xmlns:android="http://schemas.android.com/apk/res/android"
     android:initialLayout="@layout/widget"
     android:minHeight="84dp"
     android:minWidth="84dp"
     android:updatePeriodMillis="86400000" >

 </appwidget-provider>

上面几个参数意义很明确，initialLayout就是指小工具所使用的初始化布局，minHeight和minWidth定义小工具的最小尺寸，updatePeriodMillis定义了小工具的自动更新周期，毫秒为单位，每隔一个周期，小工具的自动更新就会触发。

3 定义小工具类，继承AppWidgetProvider：

 public class MyAppWidgetProvider extends AppWidgetProvider {

     public static final String TAG = "MyAppWidgetProvider";
     public static final String CLICK_ACTION = "com.example.action.CLICK";
     private static RemoteViews mRemoteViews;

     /**
      * 每删除一次窗口小部件就调用一次
      */
     @Override
     public void onDeleted(Context context, int[] appWidgetIds) {
         super.onDeleted(context, appWidgetIds);
         Log.i(TAG, "onDeleted");
     }

     /**
      * 当最后一个该窗口小部件删除时调用该方法，注意是最后一个
      */
     @Override
     public void onDisabled(Context context) {
         super.onDisabled(context);
         Log.i(TAG, "onDisabled");
     }

     /**
      * 当该窗口小部件第一次添加到桌面时调用该方法，可添加多次但只第一次调用
      */
     @Override
     public void onEnabled(Context context) {
         super.onEnabled(context);
         Log.i(TAG, "onEnabled");
     }

     /**
      * 接收窗口小部件点击时发送的广播
      */
     @Override
     public void onReceive(final Context context, Intent intent) {
         super.onReceive(context, intent);
         Log.i(TAG, "onReceive : action = " + intent.getAction());

         //这里判断是自己的action，做自己的事情，比如小工具被点击了要干啥，这里是做来一个动画效果
         if (intent.getAction().equals(CLICK_ACTION)) {
             Toast.makeText(context, "clicked it", Toast.LENGTH_SHORT).show();

             new Thread(new Runnable() {
                 @Override
                 public void run() {
                     Bitmap srcbBitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.clear_fan);
                     for (int i = 0; i < 20; i++) {
                         float degree = (i * 90)%360;
                         mRemoteViews.setImageViewBitmap(R.id.imageView1, rotateBitmap(context, srcbBitmap, degree));
                         Intent intentClick = new Intent();
                         intentClick.setAction(CLICK_ACTION);
                         PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, intentClick, 0);
                         mRemoteViews.setOnClickPendingIntent(R.id.imageView1, pendingIntent);
                         AppWidgetManager appWidgetManager = AppWidgetManager.getInstance(context);
                         appWidgetManager.updateAppWidget(
                                 new ComponentName(context, MyAppWidgetProvider.class), mRemoteViews);
                         try {
                             Thread.sleep(100);
                         } catch (InterruptedException e) {
                             e.printStackTrace();
                         }
                     }

                 }
             }).start();

         }

     }

     /**
      * 每次窗口小部件被点击更新都调用一次该方法
      */
     @Override
     public void onUpdate(Context context, AppWidgetManager appWidgetManager,
             int[] appWidgetIds) {
         super.onUpdate(context, appWidgetManager, appWidgetIds);
         Log.i(TAG, "onUpdate");

         final int counter = appWidgetIds.length;
         Log.i(TAG, "counter = " + counter);
         for (int i = 0; i < counter; i++) {
             int appWidgetId = appWidgetIds[i];
             onWidgetUpdate(context, appWidgetManager, appWidgetId);
         }

     }

     /**
      * 窗口小部件更新
      *
      * @param context
      * @param appWidgeManger
      * @param appWidgetId
      */
     private void onWidgetUpdate(Context context,
             AppWidgetManager appWidgeManger, int appWidgetId) {

         Log.i(TAG, "appWidgetId = " + appWidgetId);
         mRemoteViews = new RemoteViews(context.getPackageName(), R.layout.widget);

         // "窗口小部件"点击事件发送的Intent广播
         Intent intentClick = new Intent();
         intentClick.setAction(CLICK_ACTION);
         PendingIntent pendingIntent = PendingIntent.getBroadcast(context, 0, intentClick, 0);
         mRemoteViews.setOnClickPendingIntent(R.id.imageView1, pendingIntent);
         appWidgeManger.updateAppWidget(appWidgetId, mRemoteViews);
     }

     private Bitmap rotateBitmap(Context context, Bitmap srcbBitmap, float degree) {
         Matrix matrix = new Matrix();
         matrix.reset();
         matrix.setRotate(degree);
         Bitmap tmpBitmap = Bitmap.createBitmap(srcbBitmap, 0, 0, srcbBitmap.getWidth(),
                 srcbBitmap.getHeight(), matrix, true);
         return tmpBitmap;
     }

 }

4 最后一步，在AndroidManifest.xml中声明小工具类：

 <receiver
     android:name=".MyAppWidgetProvider"
     android:icon="@drawable/df_fan_slow" >
     <meta-data
         android:name="android.appwidget.provider"
         android:resource="@xml/appwidget_provider_info" >
     </meta-data>

     <intent-filter>
         <action android:name="com.example.action.CLICK" />
         <action android:name="android.appwidget.action.APPWIDGET_UPDATE" />
     </intent-filter>
 </receiver>

说明：根据我调研的结果，大家都说android.appwidget.action.APPWIDGET_UPDATE是必须要提供的，我试了下，如果不加，就无法出现在手机小工具列表中。其他action可以根据需要自行添加。

其中AppWidgetProvider中的几个回调方法：onEnabled,onDisabled,onDeleted,onUpdated会自动被其onReceive方法在合适的时间调用，确切来说是，当广播到来以后，AppWidgetProvider会自动根据广播的action通过onReceive方法来自动派发广播，也就是调用上述几个方法。android源码里说的很清楚：

 // BEGIN_INCLUDE(onReceive)
 public void onReceive(Context context, Intent intent) {
     // Protect against rogue update broadcasts (not really a security issue,
     // just filter bad broacasts out so subclasses are less likely to crash).
     String action = intent.getAction();
     if (AppWidgetManager.ACTION_APPWIDGET_UPDATE.equals(action)) {
         Bundle extras = intent.getExtras();
         if (extras != null) {
             int[] appWidgetIds = extras.getIntArray(AppWidgetManager.EXTRA_APPWIDGET_IDS);
             if (appWidgetIds != null && appWidgetIds.length > 0) {
                 this.onUpdate(context, AppWidgetManager.getInstance(context), appWidgetIds);
             }
         }
     }
     else if (AppWidgetManager.ACTION_APPWIDGET_DELETED.equals(action)) {
         Bundle extras = intent.getExtras();
         if (extras != null && extras.containsKey(AppWidgetManager.EXTRA_APPWIDGET_ID)) {
             final int appWidgetId = extras.getInt(AppWidgetManager.EXTRA_APPWIDGET_ID);
             this.onDeleted(context, new int[] { appWidgetId });
         }
     }
     else if (AppWidgetManager.ACTION_APPWIDGET_OPTIONS_CHANGED.equals(action)) {
         Bundle extras = intent.getExtras();
         if (extras != null && extras.containsKey(AppWidgetManager.EXTRA_APPWIDGET_ID)
                 && extras.containsKey(AppWidgetManager.EXTRA_APPWIDGET_OPTIONS)) {
             int appWidgetId = extras.getInt(AppWidgetManager.EXTRA_APPWIDGET_ID);
             Bundle widgetExtras = extras.getBundle(AppWidgetManager.EXTRA_APPWIDGET_OPTIONS);
             this.onAppWidgetOptionsChanged(context, AppWidgetManager.getInstance(context),
                     appWidgetId, widgetExtras);
         }
     }
     else if (AppWidgetManager.ACTION_APPWIDGET_ENABLED.equals(action)) {
         this.onEnabled(context);
     }
     else if (AppWidgetManager.ACTION_APPWIDGET_DISABLED.equals(action)) {
         this.onDisabled(context);
     }
 }
 // END_INCLUDE(onReceive)