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)