BroadcastReceiver for WALLPAPER_CHANGED多次调用onReceive()：

Question

我有一个BroadcastReceiver，并声明如下：

<receiver
    android:name="com.services.Receiver"
    android:enabled="true"
    android:exported="true" >
    <intent-filter android:priority="999" >
        <action android:name="android.intent.action.WALLPAPER_CHANGED" />
    </intent-filter>
</receiver>

接受者是：

@Override
public void onReceive(final Context context, final Intent intent)
{
    change_wallpepar.myPrefs = context.getSharedPreferences("myPrefs", Context.MODE_PRIVATE);
    new Handler().postDelayed(new Runnable()
    {
        @Override
        public void run()
        {
            Log.d("MAYUR", "<< wallpepar changed >>");
            if (change_wallpepar.myPrefs.getLong("temp_for_change", 1) == 0)
            {
                context.stopService(new Intent(context, change_wallpepar.class));
            }
            else
            {
                SharedPreferences.Editor e = change_wallpepar.myPrefs.edit();
                e.putLong("temp_for_change", 0);
                e.commit();
            }
        }
    }, 4000);
}

我换墙纸的时候应该叫一次。它确实按照我的预期工作了一段时间，几分钟后，它多次调用onreceive() (10-18次)，尽管墙纸的改变只做了一次。更奇怪的是，它在三星Galaxy平板电脑4.4.2版上工作得很好，但在摩托罗拉(MotoE4.4.4)上却没有工作。

我的服务：

public class change_wallpepar extends Service {

    @Override
    public void onCreate()
    {
        // TODO Auto-generated method stub
        super.onCreate();
        mytimer = new Timer();
        wpm = WallpaperManager.getInstance(change_wallpepar.this);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId)
    {
        // TODO Auto-generated method stub
        myPrefs = getSharedPreferences("myPrefs", MODE_PRIVATE);
        intervall = myPrefs.getLong("someValue", 60000);

        path_of_wallpepar.clear();
        path_of_wallpepar.add("" + "/storage/emulated/0/Android/data/WallpeparAppHistoryPhotos/514.jpg");
        path_of_wallpepar.add("" + "/storage/emulated/0/Android/data/WallpeparAppHistoryPhotos/513.jpg");

        DisplayImageOptions defaultOption = new DisplayImageOptions.Builder().cacheInMemory(true).cacheOnDisk(true).bitmapConfig(Bitmap.Config.RGB_565).build();
        ImageLoaderConfiguration config = new ImageLoaderConfiguration.Builder(change_wallpepar.this).defaultDisplayImageOptions(defaultOption).build();
        ImageLoader.getInstance().init(config);

        mytimer.schedule(new TimerTask()
        {
            @Override
            public void run()
            {

                try
                {
                    wpm.setBitmap(ImageLoader.getInstance().loadImageSync("file://" + path_of_wallpepar.get(temper)));

                }
                catch (IOException e)
                {
                    e.printStackTrace();
                }

                temper++;

                if (temper == path_of_wallpepar.size())
                    temper = 0;

                SharedPreferences.Editor e = change_wallpepar.myPrefs.edit();
                e.putLong("temp_for_change", 1);
                e.commit();

                Log.e("MAYUR", "wallpepar seted");

            }
        }, 0, intervall);

        return super.onStartCommand(intent, flags, startId);

    }

    @Override
    public IBinder onBind(Intent intent)
    {
        // TODO Auto-generated method stub

        return null;
    }

    public void onDestroy()
    {
        Toast.makeText(this, "Service Destroyed", Toast.LENGTH_SHORT).show();
        Vibrator v = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE);
        v.vibrate(1000);
        mytimer.cancel();
        super.onDestroy();
    }

}

我的Logcat输出是：

## Logcat ##
04-16 11:06:30.654: E/MAYUR(3405): wallpepar seted
04-16 11:06:34.636: D/MAYUR(3405): << wallpepar changed >>
04-16 11:06:59.584: E/MAYUR(3405): wallpepar seted
04-16 11:07:03.551: D/MAYUR(3405): << wallpepar changed >>
04-16 11:07:30.078: E/MAYUR(3405): wallpepar seted
04-16 11:07:33.979: D/MAYUR(3405): << wallpepar changed >>
04-16 11:07:59.433: E/MAYUR(3405): wallpepar seted
04-16 11:08:03.340: D/MAYUR(3405): << wallpepar changed >>
04-16 11:08:30.029: E/MAYUR(3405): wallpepar seted
04-16 11:08:33.933: D/MAYUR(3405): << wallpepar changed >>
04-16 11:08:59.481: E/MAYUR(3405): wallpepar seted
04-16 11:09:03.383: D/MAYUR(3405): << wallpepar changed >>
04-16 11:09:30.066: E/MAYUR(3405): wallpepar seted
04-16 11:09:33.966: D/MAYUR(3405): << wallpepar changed >>
04-16 11:09:59.448: E/MAYUR(3405): wallpepar seted
04-16 11:10:03.353: D/MAYUR(3405): << wallpepar changed >>
04-16 11:10:30.049: E/MAYUR(3405): wallpepar seted
04-16 11:10:33.955: D/MAYUR(3405): << wallpepar changed >>
04-16 11:10:59.455: E/MAYUR(3405): wallpepar seted
04-16 11:11:03.350: D/MAYUR(3405): << wallpepar changed >>
04-16 11:11:30.182: E/MAYUR(3405): wallpepar seted
04-16 11:11:34.177: D/MAYUR(3405): << wallpepar changed >>
04-16 11:11:59.406: E/MAYUR(3405): wallpepar seted
04-16 11:12:03.315: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:30.025: E/MAYUR(3405): wallpepar seted
04-16 11:12:33.929: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:34.103: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:34.298: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:34.497: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:34.676: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:34.854: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:35.022: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:35.190: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:35.355: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:35.522: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:35.683: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:35.852: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:36.023: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:36.187: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:36.350: D/MAYUR(3405): << wallpepar changed >>
04-16 11:12:36.513: D/MAYUR(3405): << wallpepar changed >>

Answer 1

重复的WALLPAPER_CHANGED调用是由较小的Android设备在图像上运行裁剪周期以适应屏幕造成的。这是在AOSP码中观察到的。当屏幕比率符合或大于图像时，您就不太可能看到这种行为，因此平板电脑没有表现出这种行为。

您可以通过反复检查不想要的行为的迹象来解决这个问题：

long lastExec = System.currentTimeMillis();

@Override
public void onReceive(final Context context, final Intent intent)
{
    change_wallpepar.myPrefs = context.getSharedPreferences("myPrefs", Context.MODE_PRIVATE);
    new Handler().postDelayed(new Runnable()
    {
        @Override
        public void run()
        {
          if(System.currentTimeMillis()-lastExec>1000)
          {
            Log.d("MAYUR", "<< wallpepar changed >>");
            if (change_wallpepar.myPrefs.getLong("temp_for_change", 1) == 0)
            {
                context.stopService(new Intent(context, change_wallpepar.class));
            }
            else
            {
                SharedPreferences.Editor e = change_wallpepar.myPrefs.edit();
                e.putLong("temp_for_change", 0);
                e.commit();
            }
          }
          lastExec = System.currentTimeMillis();
        }
    }, 4000);
}

Answer 2

我不知道为什么在某些设备上会出现这种情况，但在我看来，这很可能是特定设备的问题。虽然我不能解决这个问题，但您可能会持有一个变量，一旦您的侦听器被击中并在一段时间后重置，该变量将被切换。因此，这将导致您的听者在短时间内忽略未来的呼叫。把它想成是防洪。

我知道这并不能解决你的实际问题，但我希望它能提供一个合适的解决办法。

Answer 3

很可能是设备特有的问题。

通常使用标志我猜是推荐解决方案

@Override
public void onReceive(final Context context, final Intent intent)
{
     private static boolean firstReceive = true;
    change_wallpepar.myPrefs = context.getSharedPreferences("myPrefs", Context.MODE_PRIVATE);
    new Handler().postDelayed(new Runnable()
    {
        @Override
        public void run()
        {
           if(firstReceive){
            Log.d("MAYUR", "<< wallpepar changed >>");
            if (change_wallpepar.myPrefs.getLong("temp_for_change", 1) == 0)
            {
                context.stopService(new Intent(context, change_wallpepar.class));
            }
            else
            {
                SharedPreferences.Editor e = change_wallpepar.myPrefs.edit();
                e.putLong("temp_for_change", 0);
                e.commit();
            }
        }
   ///CHANGE firstReceive BASED ON EITHER TIME SINCE LAST WALLPAPER CHANGE
   ///OR ANY OTHER PARAMETER THAT SUITS YOUR REQUIREMENT
    }, 4000);
  }
}

注意，我还没有在循环中重新设置标志，您可能应该在上次更改或之后进行，将当前的墙纸标识符保存在共享的pref中，并与其匹配，并根据需要设置标志等。

这样做的目的是解决这个问题，这样您就克服了假阳性的问题，真正改变了实际的wallpaper_change调用。这是一个Workaround，而不是问题存在的实际解决方案。