Android：一步一步实现音乐播放器(2)

public class MusicList {          public static List<Music> getMusicData(Context context){           List<Music> musicList=new ArrayList<Music>();           ContentResolver cr=context.getContentResolver();           if(cr!=null){               //获取所有歌曲                              Cursor cursor=cr.query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,                       null, null,null, MediaStore.Audio.Media.DEFAULT_SORT_ORDER);               if(null==cursor){                   return null;               }               if(cursor.moveToFirst()){                   do{                       Music m=new Music();                    String title=cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.TITLE));                    String singer=cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST));                    if("<unknown>".equals(singer)){                           singer="未知艺术家";                       }                    String album=cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ALBUM));                    long size=cursor.getLong(cursor.getColumnIndex(MediaStore.Audio.Media.SIZE));                    long time=cursor.getLong(cursor.getColumnIndex(MediaStore.Audio.Media.DURATION));                    String url=cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA));                    String name=cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DISPLAY_NAME));                    m.setTitle(title);                    m.setSinger(singer);                    m.setAlbum(album);                    m.setSize(size);                    m.setTime(time);                    m.setUrl(url);                    m.setName(name);                    musicList.add(m);                   }while(cursor.moveToNext());                   }              }           return musicList;                  }   }