java - 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手机主屏幕(应用程序进入后台)时，音乐仍在播放。

我试图在 onStop 和 onDestroy 方法中停止它，但是当我改变 Activity 时这会停止音乐，这是我不想要的(我想要在用户浏览 Activity 时继续播放音乐)。

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 和接收事件的方法中:

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.stop();
        }else{player.start();}

    }
};

在 Application 类中我这样做了:

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) {

}   

但音乐不会恢复

Answer 1

您需要在停止后重新准备播放器。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:在您的应用程序类中，在 onActivityDestroyed() 中:

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

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 .