MediaPlayer代码错误（-38,0）

Question

我试图制作一个简单的媒体播放器用于练习目的。代码如下所示。但是我得到了error (-38,0)。我知道出现此错误代码是因为我在完成同步之前尚未启动mp。但我无法解决它。

(public class MainActivity extends AppCompatActivity implements MediaPlayer.OnErrorListener, MediaPlayer.OnPreparedListener{

ArrayList<Song> songList;
MediaPlayer mp;
Uri musicUri = MediaStore.Audio.Media.INTERNAL_CONTENT_URI;

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

    ListView listView = (ListView) findViewById(R.id.list_view);

    songList = new ArrayList<>();
    getSongList();

    Collections.sort(songList, new Comparator<Song>(){
        public int compare(Song a, Song b){
            return a.getTitle().compareTo(b.getTitle());
        }
    });

    SongAdapter adapter = new SongAdapter(this, songList);
    listView.setAdapter(adapter);

    mp = new MediaPlayer();
    mp.setAudioStreamType(AudioManager.STREAM_NOTIFICATION);
    try{mp.setDataSource(MainActivity.this, musicUri);} catch (Exception e){};
    try{mp.prepareAsync();} catch (Exception e){};

    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
            onPrepared(mp);
        }
    });

}
public void getSongList(){

    ContentResolver musicResolver = getContentResolver();
    Cursor musicCursor = musicResolver.query(musicUri, null, null, null, null);

    if (musicCursor!=null && musicCursor.moveToFirst()) {
        //get columns
        int titleColumn = musicCursor.getColumnIndex(android.provider.MediaStore.Audio.Media.TITLE);
        int idColumn = musicCursor.getColumnIndex(android.provider.MediaStore.Audio.Media._ID);
        int artistColumn = musicCursor.getColumnIndex(android.provider.MediaStore.Audio.Media.ARTIST);
        do {
            Long thisId = musicCursor.getLong(idColumn);
            String thisTitle = musicCursor.getString(titleColumn);
            String thisArtist = musicCursor.getString(artistColumn);

            songList.add(new Song(thisId, thisTitle, thisArtist));
        }while (musicCursor.moveToNext());
    }

    if (musicCursor != null) {
        musicCursor.close();
    }
}

@Override
protected void onDestroy() {
    super.onDestroy();
    mp.release();
    mp = null;
}

@Override
public boolean onError(MediaPlayer mediaPlayer, int i, int i1) {
    return false;
}

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