android - 单击后退按钮时音乐播放器崩溃

Question

我制作了一个简单的音乐播放器，可以在后台播放一些歌曲。转到主屏幕并通过通知重新打开应用程序也可以。

我遇到的唯一问题是，如果我在音乐播放器 Activity 中按下后退按钮(转到父 Activity )，我的应用程序就会崩溃。有两个类， Activity MP3Player.java 和服务 MP3Service.jave。

我收到以下错误:

java.lang.RuntimeException: Unable to destroy activity {package/package.MP3Player}: java.lang.IllegalArgumentException: Service not registered: package.MP3Player$1@b135b300

你知道什么建议吗？提前致谢!

编辑 1:我在我的播放器 Activity 中像这样绑定(bind)我的播放器:MP3Player.java( Activity )

playIntent = new Intent(this, MP3Service.class);
bindService(playIntent, musicConnection, Context.BIND_AUTO_CREATE);
startService(playIntent);

我用了this教程并对其进行了修改。

编辑 3:现在我得到这个错误:

java.lang.RuntimeException: Unable to stop service package.MP3Service@b13a6f80: java.lang.IllegalStateException

MP3Service.java

public void onCreate() {
    super.onCreate();
    songPosn = 0;
    player = new MediaPlayer();
    initMusicPlayer();
}

public void initMusicPlayer() {
    player.setAudioStreamType(AudioManager.STREAM_MUSIC);
}

...

@Override
public int onStartCommand(Intent intent, int flags, int startId) {
    return START_STICKY;
}

public void setList(ArrayList<Song> theSongs) {
    songs = theSongs;
}

public class MusicBinder extends Binder {
    MP3Service getService() {
        return MP3Service.this;
    }
}

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

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

public void playSong() {
    player.reset();

    Song playSong = songs.get(songPosn);

    try {
        player.setDataSource(getApplicationContext(),
                Uri.parse(playSong.getPath()));
    } catch (Exception e) {
        Log.e("MUSIC SERVICE", "Error setting data source", e);
    }
    player.prepareAsync();
}

public void pauseMusic() {
    if (player.isPlaying()) {
        player.pause();
        length = player.getCurrentPosition();
    }
}

public void resumeMusic() {
    if (player.isPlaying() == false) {
        player.seekTo(this.length);
        player.start();
    } else {
        Toast.makeText(getApplicationContext(),
                "Please select a song to play", Toast.LENGTH_LONG).show();
    }
}

public void stopMusic() {
    player.stop();
    player.release();
    player = null;
}

// set the song
public void setSong(int songIndex) {
    songPosn = songIndex;

}

@Override
public void onPrepared(MediaPlayer mp) {
    mp.start();
}

@Override
public void onDestroy() {
    super.onDestroy();
    if (player != null) {
        try {
            player.stop();
            player.release();
        } finally {
            player = null;
        }
    }
}

MP3Player.java

    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_mp3_player);
    getActionBar().setDisplayHomeAsUpEnabled(true);

    songList = getSongList();

    listAdapter = new PlayListAdapter(this, songList);
    listMusic.setAdapter(listAdapter);

    listMusic.setOnItemClickListener(new OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int pos,
                long arg3) {
            currentSongPos = pos;
            musicSrv.setSong(currentSongPos);
            musicSrv.playSong();
        }
    });

}

private ServiceConnection musicConnection = new ServiceConnection() {
    @Override
    public void onServiceConnected(ComponentName name, IBinder service) {
        MusicBinder binder = (MusicBinder) service;
        musicSrv = binder.getService();
        musicSrv.setList(songList);
        musicBound = true;
    }

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

@Override
protected void onStart() {
    super.onStart();
    if (playIntent == null) {
        playIntent = new Intent(this, MP3Service.class);
        bindService(playIntent, musicConnection, Context.BIND_AUTO_CREATE);
        startService(playIntent);
    }
}


...

protected void onDestroy() {
    if (musicBound) {
        stopService(playIntent);
        unbindService(musicConnection);
        musicSrv = null;
    }
    super.onDestroy();
}

Answer 1

Service not registered 表示它在 unbindService() 调用期间未绑定(bind)服务。

阅读有关服务生命周期的信息:API Guide: Services

编辑:

尝试添加:

protected void onDestroy() {
  if(musicBound){
      stopService(playIntent);
      unbindService(musicConnection);
      musicSrv=null;
  }
  super.onDestroy();
}

编辑 2:

对不起我的错，你需要先调用stopService()然后调用unbindService()

stopService() 的 Android 文档指出:

Note that if a stopped service still has ServiceConnection objects bound to it with the BIND_AUTO_CREATE set, it will not be destroyed until all of these bindings are removed. See the Service documentation for more details on a service's lifecycle.