当应用进入后台时停止 MediaPlayer 服务

Question

我有一个媒体播放器服务，可以在我的应用程序后台播放音乐，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();
}

问题是，当用户更改应用程序或转到 phone 的主屏幕（应用程序进入后台）时，音乐仍在播放。

我试图用 onStop 和 onDestroy 方法停止它，但是当我改变活动时这会停止音乐，这是我不想要的（我希望音乐继续播放当用户浏览活动时）。

更新

我试过广播：

我加了

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

在音乐服务的onCreate中和接收事件的方法:

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();}

    }
};

在应用程序中 class 我这样做了：

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) {

}

但是音乐不会恢复

Answer 1

你实现了onDestroy()了吗？如果没有，我相信这可能是解决方案 - 你停止播放器或任何你正在使用的运行 onDestroy() 中的服务。

A service can be stopped by calling its stopSelf() method, or by calling Context.stopService().

Answer 2

您可以将此添加到您的应用程序中 class 以检查您的应用程序是否在前台。

public class MyLifecycleHandler implements Application.ActivityLifecycleCallbacks {
    private static int resumed;
    private static int paused;
    private static int started;
    private static int stopped;

    private static String currentActivity;

    public static String getCurrentActivity() {
        return currentActivity;
    }

    @Override
    public void onActivityCreated(Activity activity, Bundle savedInstanceState) {
        currentActivity = activity.getClass().getSimpleName();
    }

    @Override
    public void onActivityDestroyed(Activity activity) {
    }

    @Override
    public void onActivityResumed(Activity activity) {
        ++resumed;
    }

    @Override
    public void onActivityPaused(Activity activity) {
        ++paused;
        android.util.Log.w("test", "application is in foreground: " + (resumed > paused));

        // send broadcast from here to the service
        sendBroadcast()
    }

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

    @Override
    public void onActivityStarted(Activity activity) {
        ++started;
    }

    @Override
    public void onActivityStopped(Activity activity) {
        ++stopped;
        android.util.Log.w("test", "application is visible: " + (started > stopped));
    }

    public static boolean isApplicationVisible() {
        return started > stopped;
    }

    public static boolean isApplicationInForeground() {
        return resumed > paused;
    }
}

像这样将其添加到您的应用程序中：

public class MyApplication extends Application {

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

        registerActivityLifecycleCallbacks(new MyLifecycleHandler());
    }
}

在服务中收到广播后，您可以停止媒体播放器。

编辑

您需要将应用程序 class 更改为：

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) {

    }
}

Answer 3

播放器停止后需要重新准备。如果您想在您的应用程序进入后台时停止播放，并在您的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：

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，如果您想暂停播放并从您离开的地方继续播放，请进行以下更改：在您的应用程序 class 中，在 onActivityDestroyed():

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

并在 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();
            }

        }
    };

此外，请查看 MediaPlayer states。

Answer 4

除了像RoyalGriffin回答的那样使用broadcast receiver之外，音乐中断很少的问题可以通过实现LifecycleObserver接口来解决。您可以知道应用程序何时处于前台或后台，这样就不需要处理每个 activity.

的状态

使用他的方法在您的应用中实现 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);

你的 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 减少样板文件：

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"

当应用进入后台时停止 MediaPlayer 服务

Stop MediaPlayer service when app goes in Background

java

service

android

android-mediaplayer