Android可以获得所有音乐和流派，而无需嵌套游标。（MediaStore.Audio…）

Question

我的应用程序需要列出设备上的所有音乐，包括：歌曲标题、艺术家、专辑、流派等。

我所知道的获取歌曲流派的方法是创建另一个带有歌曲ID的光标，如下所示：

Uri uri = MediaStore.Audio.Genres.getContentUriForAudioId("external", (int) id);
Cursor genresCursor = mContentResolver.query(uri, genresProjection, null, null, null);

但是，如果我在列出所有歌曲的光标中执行此操作，加载时间将大大增加。（我手机上的歌曲数量，从0.5秒到大约3秒）。

这是我的代码：

// If you change this to `false`, it will load a lot quicker.
private static final boolean LOAD_GENRE = true;

private static String[] mediaProjection = {
        MediaStore.Audio.AudioColumns._ID,
        MediaStore.Audio.AudioColumns.DATA,
        MediaStore.Audio.AudioColumns.TITLE,
        MediaStore.Audio.AudioColumns.ARTIST,
        MediaStore.Audio.AudioColumns.ALBUM,
        MediaStore.Audio.AudioColumns.ALBUM_ID,
        MediaStore.Audio.AudioColumns.DURATION
};
private static String[] genresProjection = {
        MediaStore.Audio.GenresColumns.NAME
};

private ArrayList<MediaMetadataCompat> getAllMusic() {
    Uri uriAudio = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
    Cursor cursor = mContentResolver.query(uriAudio, mediaProjection, null, null, null);

    if (cursor != null) {
        int count = cursor.getCount();

        if (count > 0) {
            ArrayList<MediaMetadataCompat> audioFiles = new ArrayList<>();

            while (cursor.moveToNext()) {
                MediaMetadataCompat song = buildFromCursor(cursor);
                if (song != null) {
                    audioFiles.add(song);
                }
            }
            cursor.close();

            return audioFiles;
        }
    }
    return new ArrayList<>();
}

private MediaMetadataCompat buildFromCursor(Cursor cursor, boolean loadGenre) {
    long id = cursor.getLong(cursor.getColumnIndex(MediaStore.Audio.AudioColumns._ID));
    String data = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.AudioColumns.DATA));
    String title = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.AudioColumns.TITLE));
    String artist = ...;
    String album = ...;
    long albumId = ...;
    long duration = ...;

    //File file = new File(data);
    //if (!file.exists()) {
    //    Log.e(TAG, "Skipping song because it does not exist: " + title);
    //    return null;
    //}


    Uri uri = MediaStore.Audio.Genres.getContentUriForAudioId("external", (int) id);

    if (LOAD_GENRE) {
        String genre = null;
        Cursor genresCursor = mContentResolver.query(uri, genresProjection, null, null, null);
        if (genresCursor != null && genresCursor.moveToFirst()) {
            int genreColumnIndex = genresCursor.getColumnIndex(MediaStore.Audio.GenresColumns.NAME);
            do {
                String genreColumn = genresCursor.getString(genreColumnIndex);
                if (genre == null) {
                    genre = genreColumn;
                } else {
                    genre += " " + genre;
                }
            } while (genresCursor.moveToNext());
            genresCursor.close();
        }
    }

    // Workaround to avoid ANOTHER cursor to load album art.
    Uri albumArtUri = ContentUris.withAppendedId(Uri.parse("content://media/external/audio/albumart"), albumId);

    MediaMetadataCompat.Builder builder = new MediaMetadataCompat.Builder()
            .putString(MediaMetadataCompat.METADATA_KEY_MEDIA_ID, String.valueOf(id))
            .put...
            .put...;


    return builder.build();
}

有什么方法可以改进这段代码，以避免嵌套的光标？我已经找到了专辑艺术的解决方法。有可能以某种方式将它们结合起来吗？一个CursorJoiner是否适用于此？问题是，要想获得这一类型，你需要有媒体id。谢谢。




Answer 1

SO用户Suhaib Roomey最近发布了这篇文章（从mediastore的audio_流派地图获取流派id和音频id）。也许它能帮助你实现目标

 String[] genresProjection = {
        Audio.Genres.Members.AUDIO_ID,
        Audio.Genres.Members.GENRE_ID
 };
       context.getContentResolver().query(Uri.parse("content://media/external/audio/genres/all/members"), genresProjection, null, null, null);