在android中的存储器中查找mp3歌曲

我正在尝试制作一个应用程序来查找所有mp3歌曲，这段代码就是我得到的，但是我无法测试这段代码，因为它正在崩溃，没有任何错误，我做错了什么

我的班级要找到歌曲：

   public class SongsManager {
    private ArrayList<Song> songsList;

    public ArrayList<Song> getMp3Songs(Context ctx) {
        Uri allSongsUri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
        String selection = MediaStore.Audio.Media.IS_MUSIC + " != 0";
        Cursor cursor =  ctx.getContentResolver().query(allSongsUri, null, null, null, selection);
        if (cursor != null) {
            if (cursor.moveToFirst()) {
                do {
                    Song song = new Song(cursor.getInt(cursor.getColumnIndex(MediaStore.Audio.Media._ID)),
                            cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DISPLAY_NAME)),
                            cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.ARTIST)),
                            cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Media.DATA)));
                    songsList.add(song);
                } while (cursor.moveToNext());
            }
            cursor.close();
        }
        return songsList;
    }
}

---

您应用了错误的语法。“选择”不正确，因为这是排序顺序的所在

例如：

         private final Uri uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
         public Cursor getAllTracks(Context context) {
    // gets all tracks

    ContentResolver cr = context.getContentResolver();
    final String[] columns = {track_id, track_no, artist, track_name,
            album, duration, path, year, composer};
    return cr.query(uri, columns, null, null, null);
} 

从文件中：

    query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)

---

查询给定的URI，在结果集上返回一个光标。

“因为正在崩溃”--使用LogCat检查与崩溃相关的Java堆栈跟踪：此处出现一些错误：Cursor Cursor=ctx.getContentResolver（）.Query（allSongsUri，null，null，null，selection）；你帮了大忙！谢谢你，娜达，谢谢你

         private final Uri uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
         public Cursor getAllTracks(Context context) {
    // gets all tracks

    ContentResolver cr = context.getContentResolver();
    final String[] columns = {track_id, track_no, artist, track_name,
            album, duration, path, year, composer};
    return cr.query(uri, columns, null, null, null);
} 

    query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder)