Activity 具有绑定服务的生命周期

Question

我正在尝试学习 Android 服务，但遇到了一些麻烦。

我有一个带有 MediaPlayer 的简单服务，可以播放来自互联网的一些流媒体。我将服务绑定到我的 MainActivity，在服务上设置 URL 并开始播放流。这很好用。该服务立即成为带有通知的前台服务。我可以成功地从 MainActivity 更改 URL，然后开始新的流。但是，有几件事我想实现。

我不希望在 MainActivity 对用户可见时收到通知，仅当用户按下主页按钮或后退按钮时我希望服务开始在前台播放。当用户单击通知时，我希望 MainActivity 重新打开并且流不间断。这是否意味着我的 MainActivity 永远不会被摧毁？

截至目前，当我按下主页按钮时，流继续播放并且单击通知使 MainActivity 重新创建服务（流停止并再次开始播放）。我实际上希望服务永远不会停止播放，除非用户通过在多任务处理中滑动它来杀死应用程序 window（就像 Spotify 那样）。

我的服务代码如下：

public class StreamService extends Service implements
    MediaPlayer.OnPreparedListener, MediaPlayer.OnErrorListener,
    MediaPlayer.OnCompletionListener {

    private MediaPlayer player;
    private final IBinder musicBind = new StreamBinder();
    private StreamInfo mCurrentStream;
    private static final int NOTIFY_ID = 1;

    public void onCreate() {
        super.onCreate();
        initMusicPlayer();
    }

    public void initMusicPlayer() {
        player = new MediaPlayer();
        player.setWakeMode(getApplicationContext(),
            PowerManager.PARTIAL_WAKE_LOCK);
        player.setAudioStreamType(AudioManager.STREAM_MUSIC);
        player.setOnPreparedListener(this);
        player.setOnCompletionListener(this);
        player.setOnErrorListener(this);
    }

    public class StreamBinder extends Binder {
        public StreamService getService() {
            return StreamService.this;
        }
    }

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

    @Override
    public boolean onUnbind(Intent intent) {
        player.stop();
        player.release();
        return false;
    }

    public void playStream() {
        player.reset();
        try {
            player.setDataSource(this, mCurrentStream.getUrl());
        } catch (Exception e) {
            Log.e("MUSIC SERVICE", "Error setting data source", e);
        }
        player.prepareAsync();
    }

    public void setStream(StreamInfo stream) {
        mCurrentStream = stream;
    }

    @Override
    public void onCompletion(MediaPlayer mp) {
    }

    @Override
    public boolean onError(MediaPlayer mp, int what, int extra) {
        mp.reset();
        return false;
    }

    @Override
    public void onPrepared(MediaPlayer mp) {
        mp.start();
        Intent notIntent = new Intent(this, MainActivity.class);
        notIntent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
        PendingIntent pendInt = PendingIntent.getActivity(this, 0,
            notIntent, PendingIntent.FLAG_UPDATE_CURRENT);

        Notification.Builder builder = new Notification.Builder(this);

        builder.setContentIntent(pendInt)
            .setSmallIcon(R.drawable.ic_action_navigation_chevron_right)
            .setTicker(mCurrentStream.getTitle())
            .setOngoing(true)
            .setContentTitle("Playing")
            .setContentText(mCurrentStream.getTitle());
        Notification not = builder.build();
        startForeground(NOTIFY_ID, not);
    }

    @Override
    public void onDestroy() {
        stopForeground(true);
    }
}

还有我的MainActivity：

public class MainActivity extends AppCompatActivity implements ServiceConnection {

    private static final String TAG = MainActivity.class.getSimpleName();

    private StreamService mStreamService;
    private boolean musicBound = false;
    private Intent playIntent;

    @Override
    protected void onStart() {
        super.onStart();
        if (playIntent == null) {
            playIntent = new Intent(this, StreamService.class);
            bindService(playIntent, this, MainActivity.BIND_AUTO_CREATE);
            startService(playIntent);
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        startStreaming();
    }


    private void startStreaming() {
        mStreamService.setStream(getSelectedStream());
        mStreamService.playStream();
    }

    @Override
    protected void onDestroy() {
        stopService(playIntent);
        mStreamService = null;
        super.onDestroy();
    }

    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        StreamService.StreamBinder binder = (StreamService.StreamBinder) service;
        mStreamService = binder.getService();
        musicBound = true;
        startStreaming();
    }

    @Override
    public void onServiceDisconnected(ComponentName name) {
        musicBound = false;
    }

    public StreamInfo getSelectedStream() {
        //Returns some stream from a widget
    }
}

Of course there is a widget in my MainActivity with a listener and when the selection changes the startStreaming() method is called.

任何人都可以指出正确的方向吗？

Answer 1

I do not want a notification when the MainActivity is visible to the user, only when the user presses the home button or back button I want the service to start playing in the foreground.

在您的服务中保留一个布尔标志以指示是否绑定了某些内容。在显示通知之前检查标志。例如：

@Override
public IBinder onBind(Intent intent) {
    mBound = true;
    hideNotifications();
    return musicBind;
}

@Override
public void onRebind(Intent intent) {
    mBound = true;
    hideNotifications();
}

When the user clicks on the notification I want the MainActivity to reopen and the stream uninterrupted. Does this mean my MainActivity can never be destroyed?

您需要解绑您的activityonStop()。

As of now, when I press the home button the stream keeps playing and clicking the notification makes the MainActivity recreate the service (the stream stops and starts to play again). I actually want the Service to never stop playing unless the user kills the app by swiping it in the multitasking window (like Spotify does it).

您的 Activity 的

onStart() 检查服务是否运行并重新绑定到它而不是重新创建它。如果不是运行 - 创建并绑定。

Activity 具有绑定服务的生命周期

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