MediaStore Audio不显示来自Google Play音乐的歌曲

Question

我有以下代码来获取设备中的所有音乐。我的设备已通过Google's Play Music app下载了音乐..但这些文件不会显示..任何想法为什么......

这是我的代码：

String[] musicProjParams = { MediaStore.Audio.Media._ID,
            MediaStore.Audio.Media.DATA,
            MediaStore.Audio.Media.DISPLAY_NAME,
            MediaStore.Audio.Media.TITLE, 
            MediaStore.Video.Media.SIZE,
            MediaStore.Audio.Media.MIME_TYPE,
            MediaStore.Audio.Media.ALBUM,
            MediaStore.Audio.Media.ALBUM_ID,
            MediaStore.Audio.Media.ARTIST};
    //String[] cont = { "audio/mpeg" };
    String selection = MediaStore.Audio.Media.IS_MUSIC + " != 0";
    musicCursor = getContentResolver().query(
            MediaStore.Audio.Media.EXTERNAL_CONTENT_URI, musicProjParams,
            selection,
            null, 
            "UPPER(" +MediaStore.Audio.Media.TITLE + " )ASC");
    mAdapter = new DRPMusicFromPhoneAdapter(getApplicationContext(),
            android.R.layout.simple_list_item_1, musicCursor,
            new String[] { "_id, MediaStore.Audio.Media.TITLE" },
            new int[] { android.R.id.text1 },albumArtMap);
    _searchResultsView.setAdapter(mAdapter);