java - ANDROID:MediaPlayer 显示错误 (1, -19)

Question

我正在开发一个服务，它播放从ArrayList 中挑选的歌曲。 当我使用 prepare() 和 prepareAsync() 方法时，问题就来了，所以这里是代码:

public class MusicService extends Service implements MediaPlayer.OnPreparedListener{
    private final static int DEF_VALUE = -1;
    private Context mContext;
    private ArrayList<Song> mSongsList;
    private MediaPlayer mPlayer;
    private boolean isPlaying = false;
    private int mPosition;

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

    @Override
    public void onCreate(){
        super.onCreate();
        mContext = getApplicationContext();
        mSongsList = new ArrayList<Song>();
        mPlayer = new MediaPlayer();
        setMusicPlayer();
    }

    public void setMusicPlayer(){
        //Setting player properties
        mPlayer.setWakeMode(mContext, PowerManager.PARTIAL_WAKE_LOCK);
        mPlayer.setAudioSessionId(AudioManager.STREAM_MUSIC);
        mPlayer.setOnPreparedListener(this);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        int mCommand = intent.getIntExtra("CMD", DEF_VALUE);
        int mTrackSelected = intent.getIntExtra("TRACK_CLICKED", DEF_VALUE);

        /** SERVICE COMMANDS
         *  0 = SERVICE PERMISSIONS
         *  1 = PLAY_PAUSE
         *  2 = NEXT TRACK
         *  3 = PREV TRACK
         *  4 = SONG IN LIST
         */

        switch (mCommand){
            case 0:
                GetTracks mGetSongs = new GetTracks();
                mSongsList = mGetSongs.listAllSongs(mContext);
                Log.d("test size arrayList", ""+mSongsList.size());
                break;
            case 1:
                setPlayPause();
                break;
            case 2:
                skipNextTrack();
                break;
            case 3:
                skipPrevTrack();
                break;
            case 4:
                if(mTrackSelected != DEF_VALUE){
                    mPosition = mTrackSelected;
                    setSongToPlay(mPosition);
                }
                break;
            default:
                Log.d("error cmd", "You shouldn't be here!");
                break;
        }

        return START_STICKY;
    }

    private void skipPrevTrack() {
        Log.d("method called:", "skipPrevTrack()");
        if(mPosition == 0){
            setSongToPlay(mPosition = mSongsList.size()-1);
        } else setSongToPlay(--mPosition);
        Log.d("test mPosition service", ""+mPosition);
    }

    private void skipNextTrack() {
        Log.d("method called:", "skipNextTrack()");
        if(mPosition == mSongsList.size()-1){
            setSongToPlay(mPosition = 0);
        } else setSongToPlay(++mPosition);
        Log.d("test mPosition service", ""+mPosition);
    }


    private void setSongToPlay(int pos) {
        Log.d("method called:", "setSongToPlay("+pos+")");
        startSong(mSongsList.get(pos).getSongUri());
    }
    private void startSong(Uri uri){

        try{
            mPlayer.reset();
            mPlayer.setDataSource(mContext, uri);
            mPlayer.prepareAsync();

            /** +++WORKS FINE WITH THIS CODE+++
             mPlayer = MediaPlayer.create(mContext, uri);
             mPlayer.start();
             */

        } catch (Exception e){
            e.printStackTrace();
        }
    }

    private void setPlayPause() {
        Log.d("method called:", "setPlayPause()");
    }

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

日志:

 12-19 16:12:18.325 4013-4013/sebbsoft.myApp D/method called:: setSongToPlay(3)
12-19 16:12:18.341 4013-4013/sebbsoft.myApp D/test song playing: Fiori del male ft. Sfera Ebbasta
12-19 16:12:18.363 4013-4013/sebbsoft.myApp D/MediaPlayer: setSubtitleAnchor in MediaPlayer
12-19 16:12:18.428 4013-4028/sebbsoft.myApp E/MediaPlayer: error (1, -19)

我该如何解决？

Answer 1

终于解决了!经过大量的试验和错误! 这是对我造成的原因:

mMediaPlayer.setAudioSessionId(AudioManager.STREAM_MUSIC);

setAudioSessionId 的 API 文档没有指出任何替代方案或任何关于仍在使用它的问题，这使得调试变得困难。但是我在它下面看到了 setAudioStreamType，它已被弃用并建议 setAudioAttributes相反，在 API 21 中添加了 w/c。

所以我把上面的代码改成这样:

if (android.os.Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
        mMediaPlayer.setAudioAttributes(new AudioAttributes.Builder()
                .setUsage(AudioAttributes.USAGE_MEDIA)
                .setContentType(AudioAttributes.CONTENT_TYPE_MUSIC)
                .build());
} else {
        mMediaPlayer.setAudioStreamType(AudioManager.STREAM_MUSIC);
}

现在可以了!

顺便说一句，如您所见，即使在 API 21 中添加了 setAudioAttributes，我也只检查了版本 N(API 24)及更高版本，而不是 LOLLIPOP，因为我只遇到这个问题在 Nougat 设备上，setAudioSessionId 对我来说适用于 Marshmallow 设备，所以...不想破坏任何已经在工作的东西。

我确实希望有人能过来解释一下为什么会发生这种情况以及错误的真正含义。

希望这可以减轻任何人几天的头痛 :)

编辑: 对于任何使用谷歌搜索的人，我也将原来的 mMediaPlayer.setAudioSessionId 更改为 mMediaPlayer.setAudioStreamType，正如 Eugen Pechanec 所指出的。有关详细信息，请参阅他的评论和答案。 您还希望将检查 Build.VERSION_CODES.N 更改为 Build.VERSION_CODES.LOLLIPOP。