//扫描本地音乐文件，返回艺术家列表 需要库MediaPlayer.framework  -(NSArray*) findArtistList {      NSMutableArray *artistList = [[NSMutableArray alloc]init];      MPMediaQuery *listQuery = [MPMediaQuery playlistsQuery];//播放列表      NSArray *playlist = [listQuery collections];//播放列表数组      for (MPMediaPlaylist * list in playlist) {          NSArray *songs = [list items];//歌曲数组          for (MPMediaItem *song in songs) {              NSString *title =[song valueForProperty:MPMediaItemPropertyTitle];//歌曲名              //歌手名              NSString *artist =[[song valueForProperty:MPMediaItemPropertyArtist] uppercaseString];              if(artist!=nil&&![artistList containsObject:artist]){                  [artistList addObject:artist];              }          }      }      return artistList;  }