Android开发中如何实现一个音乐播放器功能

 public List<Mp3Info> getMp3Infos() {   Cursor cursor = getContentResolver().query(     MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null, null, null,     MediaStore.Audio.Media.DEFAULT_SORT_ORDER);   List<Mp3Info> mp3Infos = new ArrayList<Mp3Info>();   for (int i = 0; i < cursor.getCount(); i++) {     Mp3Info mp3Info = new Mp3Info();     cursor.moveToNext();     long id = cursor.getLong(cursor       .getColumnIndex(MediaStore.Audio.Media._ID));  //音乐id     String title = cursor.getString((cursor        .getColumnIndex(MediaStore.Audio.Media.TITLE)));//音乐     String artist = cursor.getString(cursor       .getColumnIndex(MediaStore.Audio.Media.ARTIST));//艺术家     long duration = cursor.getLong(cursor       .getColumnIndex(MediaStore.Audio.Media.DURATION));//时长     long size = cursor.getLong(cursor       .getColumnIndex(MediaStore.Audio.Media.SIZE)); //文件大小     String url = cursor.getString(cursor       .getColumnIndex(MediaStore.Audio.Media.DATA));       //文件路径   int isMusic = cursor.getInt(cursor     .getColumnIndex(MediaStore.Audio.Media.IS_MUSIC));//是否为音乐   if (isMusic != 0) {   //只把音乐添加到集合当中     mp3Info.setId(id);     mp3Info.setTitle(title);     mp3Info.setArtist(artist);     mp3Info.setDuration(duration);     mp3Info.setSize(size);     mp3Info.setUrl(url);     mp3Infos.add(mp3Info);     }   } return mp3Infos; }