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我有一个经常性的警报，它触发了一个 BroadcastReceiver，它启动了一个使用 MediaPlayer 播放声音的 IntentService。但是，我的 OnCompletionListener （用于释放资源）没有被调用，因为来自 IntentService 的线程在声音结束之前就死了，并且我在日志中收到一条警告消息：

Handler{4072a788} sending message to a Handler on a dead thread

在调用 oncompletionlistener 之前，如何保持线程处于活动状态。还是有更好的方法来实现我想要的？

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2 回答 2

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对于通过本地服务播放的 Controll 媒体播放器，最好将媒体播放器引用发送给其他类，例如 CarefulMediaPlayer(mp, this);。您处理此类中的所有媒体播放器属性。我认为它对你有帮助。

谢谢

于 2012-12-14T08:55:44.380 回答
0

我在这个问题上挣扎了一段时间，最后我使用下面的类让它正常工作。这个想法是使用一个带有 Looper 的线程，该线程保持活动状态并处理所有 MediaPlayer 逻辑。

如果服务收到明确的停止消息，我只会退出 looper 并清理线程

public class PlayService extends IntentService {
private static PowerManager.WakeLock wakeLock;
private static final String TAG = "PlayService";
private static String LOCK_NAME = TAG;
public static final String EXTRA_FILE = "file";
public static final String ACTION_PLAY = "play";
private static final String ACTION_STOP = "stop";
public static final int MSG_START = 1;
public static final int MSG_STOP = 2;

public PlayService(String name) {
    super(name);
}

public PlayService() {
    super("PlayService");
}

@Override
public void onCreate() {
    super.onCreate();
}

@Override
protected void onHandleIntent(Intent intent) {
    Message msg = new Message();
    if (ACTION_PLAY.equalsIgnoreCase(intent.getAction())) {
        String fileName = intent.getExtras().getString(EXTRA_FILE);
        msg.what = MSG_START;
        msg.obj = fileName;
    } else if (ACTION_STOP.equalsIgnoreCase(intent.getAction())) {
        msg.what = MSG_STOP;
    }
    try {
        PlayMediaThread.getInstance(this).sendMessage(msg);
    } catch (InterruptedException e) {
        Log.e(TAG, e.getMessage());
    }
}

public static PowerManager.WakeLock acquireLock(Context context) {
    if (wakeLock == null || !wakeLock.isHeld()) {
        PowerManager powerManager = (PowerManager) context
                .getSystemService(Context.POWER_SERVICE);
        wakeLock = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
                LOCK_NAME);
        wakeLock.setReferenceCounted(true);
        wakeLock.acquire();
    }
    return wakeLock;
}

public static void releaseLock(Context context) {
    if (wakeLock != null && wakeLock.isHeld()) {
        wakeLock.release();
    }
}

 }

class PlayMediaThread extends Thread implements OnCompletionListener,
    OnErrorListener, OnPreparedListener {
private static Semaphore semaphore = new Semaphore(0);
private static Handler handler;
private static Looper myLooper;
private static Context context;
private static String currentFileName;
private static MediaPlayer player;
private static PlayMediaThread instance;
private static final String TAG = "PlayMediaThread";

private PlayMediaThread(Context context) throws InterruptedException {
    super(TAG);
    PlayMediaThread.context = context;
    start();
    // To insure that the looper was initialized correctly before return an
    // instance
    semaphore.acquire();
}

public static PlayMediaThread getInstance(Context context)
        throws InterruptedException {
    if (instance == null) {
        instance = new PlayMediaThread(context);
    }
    PlayMediaThread.context = context;
    return instance;
}

public void sendMessage(Message msg) {
    handler.sendMessage(msg);
}

public void quitLooper() {
    try {
        if (myLooper != null) {
            myLooper.quit();
            Log.i(TAG, "After quit");

        }
    } catch (Exception ex) {
        Log.e(TAG, ex.getMessage());
    }
}

@Override
public void run() {
    Looper.prepare();
    myLooper = Looper.myLooper();
    handler = new Handler() {
        @Override
        public void handleMessage(Message msg) {
            if (msg.what == PlayService.MSG_START) {
                startPlayer((String) msg.obj);
            } else if (msg.what == PlayService.MSG_STOP) {
                // when stop command is coming from the activity i.e. user
                // explicitly clicked stop, I quit the looper and
                // clean the thread
                stopPlayer(true);
            }
        }
    };
    semaphore.release();
    Log.i(TAG, "Before Loop");
    Looper.loop();      
}

private void stopPlayer(boolean clean) {                
    if (player != null) {
        if (player.isPlaying()) {
            player.stop();
        }
        player.release();
        player = null;
    }
    if (clean) {
                    PlayService.releaseLock(context);
        quitLooper();
        instance = null;

    }
}

private void startPlayer(String fileName) {
    if (player != null && player.isPlaying() && currentFileName != null
            && currentFileName.equalsIgnoreCase(fileName)) {
        return;
    }
    currentFileName = fileName;
    stopPlayer(false);

    player = new MediaPlayer();
    player.setOnCompletionListener(this);
    player.setOnErrorListener(this);
    player.setOnPreparedListener(this);

    try {
        player.setDataSource(context, Uri.parse(currentFileName));
        player.prepare();
        player.start();
        PlayService.acquireLock(context);
    } catch (Exception e) {
        Log.e(TAG, e.getMessage());
    }
}

@Override
public boolean onError(MediaPlayer mp, int arg1, int arg2) {
    Log.e(TAG, "onError");      

    stopPlayer(true);

    return false;
}

@Override
public void onCompletion(MediaPlayer mp) {
    Log.d(TAG, "onCompletion");
            // Just to quit the looper and clean the thread
            stopPlayer(true);
}

@Override
public void onPrepared(MediaPlayer mp) {
    Log.d(TAG, "onPrepared");       
}

}
于 2012-12-27T22:01:11.073 回答