Question

我有一个媒体播放器服务，可以在我的应用程序的后台播放音乐，例如：

public class Music extends Service {
MediaPlayer player;

@Override
public IBinder onBind(Intent intent) {
    return null;
}

public void onCreate() {
    player = MediaPlayer.create(this, R.raw.music);
    player.setLooping(true);
}

public int onStartCommand(Intent intent, int flags, int startId) {
    player.start();
    return Service.START_NOT_STICKY;
}


public void onDestroy() {
    player.stop();
    player.release();
    stopSelf();
    super.onDestroy();
}

问题在于，当用户更改应用程序或进入手机的主屏幕（应用程序进入后台）时，音乐仍在播放。

我试图在onStop和onDestroy方法中阻止它，但当我改变我不想要的活动时，这会停止播放音乐（我希望音乐继续播放）当用户浏览活动时）。

更新

我试过广播：

我添加了

LocalBroadcastManager.getInstance(this).registerReceiver(StateReceiver, new IntentFilter("status"));

in onCreate of music Service和接收事件的方法：

private BroadcastReceiver StateReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        String status = intent.getStringExtra("status");
        if (parseInt(String.valueOf(status)) == 0) {
            player.stop();
        }else{player.start();}

    }
};

在Application类中我做到了这一点：

public class app_class extends Application implements Application.ActivityLifecycleCallbacks {
private static int resumed;
private static int paused;

private static String currentActivity;

@Override
public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
    currentActivity = activity.getClass().getSimpleName();
}
public static String getCurrentActivity() {
    return currentActivity;
}
@Override
public void onActivityStarted(Activity activity) {
}
 @Override
public void onActivityResumed(Activity activity) {
    send_status(1);
}

@Override
public void onActivityPaused(Activity activity) {
    send_status(0);
}  
 private void send_status(int status_counter) {
    Intent intent = new Intent("status");
    intent.putExtra("status", String.valueOf(status_counter));
    LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
}
@Override
public void onActivityStopped(Activity activity) {      

}
@Override
public void onActivitySaveInstanceState(Activity activity, Bundle outState) {

}
@Override
public void onActivityDestroyed(Activity activity) {

}

但音乐不会恢复

Answer 1

停止播放器后，您需要重新准备播放器。如果您想在应用程序进入后台时停止播放，并在应用程序进入前台时从头开始播放媒体。只需将您的BroadcastReceiver代码修改为此：

private BroadcastReceiver StateReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String status = intent.getStringExtra("status");
            if (parseInt(String.valueOf(status)) == 0) {
                player.stop();
            } else {
                player = MediaPlayer.create(this, R.raw.music);
                player.setLooping(true);
                player.start();
            }

        }
    };

但是，如果您要暂停播放并从您离开的位置继续播放，请进行以下更改：在您的Application类的onActivityDestroyed（）中：

@Override
public void onActivityDestroyed(Activity activity) {
    send_status(2);
}

以及在BroadcastReceiver中：

private BroadcastReceiver StateReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String status = intent.getStringExtra("status");
            if (parseInt(String.valueOf(status)) == 0) {
                player.pause();  //When app is in background and not killed, we just want to pause the player and not want to lose the current state.
            } else if (parseInt(String.valueOf(status)) == 1) {
                if (player != null)
                    player.start();  // If the player was created and wasn't stopped, it won't be null, and the playback will be resumed from where we left of.
                else {
                    // If the player was stopped, we need to prepare it once again.
                    player = MediaPlayer.create(this, R.raw.music);
                    player.setLooping(true);
                    player.start();
                }
            } else if(player != null){
                player.stop();
                player.release();
            }

        }
    };

另外，看看MediaPlayer states。

Answer 2

您可以在应用程序类中添加它，以检查您的应用程序是否在前台。

public class MyApplication extends Application {

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

        registerActivityLifecycleCallbacks(new MyLifecycleHandler());
    }
}

将此添加到您的应用程序中：

public class app_class extends Application implements Application.ActivityLifecycleCallbacks {
    private static int resumed;
    private static int paused;

    private static String currentActivity;

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

    @Override
    public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
        currentActivity = activity.getClass().getSimpleName();
    }
    public static String getCurrentActivity() {
        return currentActivity;
    }
    @Override
    public void onActivityStarted(Activity activity) {
    }
    @Override
    public void onActivityResumed(Activity activity) {
        send_status(1);
    }

    @Override
    public void onActivityPaused(Activity activity) {
        send_status(0);
    }
    private void send_status(int status_counter) {
        Intent intent = new Intent("status");
        intent.putExtra("status", String.valueOf(status_counter));
        LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
    }
    @Override
    public void onActivityStopped(Activity activity) {

    }
    @Override
    public void onActivitySaveInstanceState(Activity activity, Bundle outState) {

    }
    @Override
    public void onActivityDestroyed(Activity activity) {

    }
}

收到服务广播后，您可以停止媒体播放。

修改

您需要将应用程序类更改为：

public static ArrayList<String> ArrayofName;

Answer 3

你实现了onDestroy（）吗？如果没有，我相信这可能是解决方案 - 你停止你的播放器或你在onDestroy（）中运行服务的任何东西。

可以通过调用stopSelf（）方法或通过调用来停止服务调用Context.stopService（）。

Answer 4

除了使用RoyalGriffin回答的广播接收器外，音乐中断很少的问题可以通过实现LifecycleObserver接口来解决。您可以知道应用何时处于前台或后台，这样就无需处理每个活动的状态。

使用他的方法在您的应用中实施Application.ActivityLifecycleCallbacks @OnLifecycleEvent(Lifecycle.Event.ON_STOP)和@OnLifecycleEvent(Lifecycle.Event.ON_START)

然后将此行添加到onCreate（）

ProcessLifecycleOwner.get().getLifecycle().addObserver(this);

您的app_class应该是这样的：

    public class app_class extends Application implements LifecycleObserver, 
    Application.ActivityLifecycleCallbacks{
    private static int resumed;
    private static int paused;

    private static String currentActivity;

    @Override
    public void onCreate() {
        super.onCreate();
        registerActivityLifecycleCallbacks(this);
        ProcessLifecycleOwner.get().getLifecycle().addObserver(this);
    }

   @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
    private void onAppBackgrounded() {
        Log.d(TAG, "App in background");
        send_status(0, this);
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    private void onAppForegrounded() {
        Log.d(TAG, "App in foreground");
        send_status(1, this);
    }

    @Override
    public void onActivityCreated(Activity activity, Bundle 
    savedInstanceState) {
        currentActivity = activity.getClass().getSimpleName();
    }
    public static String getCurrentActivity() {
        return currentActivity;
    }
    @Override
    public void onActivityStarted(Activity activity) {
    }
    @Override
    public void onActivityResumed(Activity activity) {
        //send_status(1);
    }

    @Override
    public void onActivityPaused(Activity activity) {
        //send_status(0);
    }
    private void send_status(int status_counter) {
        Intent intent = new Intent("status");
        intent.putExtra("status", String.valueOf(status_counter));
        LocalBroadcastManager.getInstance(this).sendBroadcast(intent);
    }
    @Override
    public void onActivityStopped(Activity activity) {

    }
    @Override
    public void onActivitySaveInstanceState(Activity activity, Bundle 
    outState) {

    }
    @Override
    public void onActivityDestroyed(Activity activity) {

    }
}

Answer 5

可以使用LifecycleObserver来简化模板：

class App : Application(), LifecycleObserver {

    @OnLifecycleEvent(Lifecycle.Event.ON_STOP)
    fun onAppInBackground() {
        sendStatus(0)
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_START)
    fun onAppInForeground() {
        sendStatus(1)
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
    fun onAppDestroyed() {
        sendStatus(2)
    }

    private fun sendStatus(statusCounter: Int) {
        val intent = Intent("status")
        intent.putExtra("status", statusCounter)
        LocalBroadcastManager.getInstance(this).sendBroadcast(intent)
    }

    override fun onCreate() {
        super.onCreate()
        ProcessLifecycleOwner.get().lifecycle.addObserver(this)
    }
}

添加到build.gradle（应用程序）

implementation "androidx.lifecycle:lifecycle-runtime:2.1.0"
implementation "androidx.lifecycle:lifecycle-extensions:2.1.0"
annotationProcessor "androidx.lifecycle:lifecycle-compiler:2.1.0"

当应用程序进入后台时停止MediaPlayer服务

5 个答案: