//查询系统的音频库

     public static List<MusicBean> getMusicInfo(Context context){

         List<MusicBean> musicList= new ArrayList<>();

         //查询音频数据库

         Cursor c = context.getContentResolver().query(MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, null, MediaStore.Audio.Media.DURATION+">=?", new String[]{"20000"}, MediaStore.Audio.Media.DEFAULT_SORT_ORDER);

         while (c.moveToNext()){

            MusicBean musicBean=new MusicBean();

             musicBean.setTitle(c.getString(c.getColumnIndex(MediaStore.Audio.Media.TITLE)));

             musicBean.setName(c.getString(c.getColumnIndex(MediaStore.Audio.Media.DISPLAY_NAME)));

             //对未知艺术家进行判断

             String singer = c.getString(c.getColumnIndex(MediaStore.Audio.Media.ARTIST));

             if(singer==null || "".equals(singer) || "<unknown>".equals(singer)){

                 singer = "未知艺术家";

             }

             musicBean.setSinger(singer);

             musicBean.setAlbum(c.getString(c.getColumnIndex(MediaStore.Audio.Media.ALBUM)));

             musicBean.setSize(c.getLong(c.getColumnIndex(MediaStore.Audio.Media.SIZE)));

             musicBean.setTime(c.getLong(c.getColumnIndex(MediaStore.Audio.Media.DURATION)));

             musicBean.setUrl(c.getString(c.getColumnIndex(MediaStore.Audio.Media.DATA)));

             musicList.add(musicBean);

         }

         //关闭游标，释放资源

         c.close();

         return musicList;

     }