Querying Playlist from MediaStore

问题:

I'm trying to query playlists in the device from MediaStore. I have followed a question asked before but I didn't get the answer.

This is how I query for playlists

public void addToPlaylist(long playlistId, Context context,
                          ArrayList<Play> playlistTracks, String playlistName) {
    int count = getPlaylistSize(playlistId, context);
    Log.d("playlist size=", "" + count);

    ContentValues[] values = new ContentValues[playlistTracks.size()];
    for (int i = 0; i < playlistTracks.size(); i++) {
        values[i] = new ContentValues();
        values[i].put(MediaStore.Audio.Playlists.Members.PLAY_ORDER, i
                      + count + 1);
        values[i].put(MediaStore.Audio.Playlists.Members.AUDIO_ID,
                      playlistTracks.get(i).getId());
        values[i].put(MediaStore.Audio.Playlists.NAME, playlistName);
    }
    ContentResolver resolver = context.getContentResolver();
    Uri uri = MediaStore.Audio.Playlists.Members.getContentUri("external",
                                                               playlistId);
    int num = resolver.bulkInsert(uri, values); 
    Log.d("songs added=", "" + num); // added
    resolver.notifyChange(Uri.parse("content://media"), null);

}

private int getPlaylistSize(long playlistId, Context context)
{
    // TODO: Implement this method
    return 0;
}
public void retrieveAllPlaylists(Context context) {

    Uri tempPlaylistURI = MediaStore.Audio.Playlists.EXTERNAL_CONTENT_URI;

    final String idKey = MediaStore.Audio.Playlists._ID;
    final String nameKey = MediaStore.Audio.Playlists.NAME;


    final String[] columns = { idKey, nameKey };

    Cursor playListCursor = context.getContentResolver().query(
        tempPlaylistURI, columns, null, null, null);

    if (playListCursor != null) {
        Log.d("playlist cursor count=", "" + playListCursor.getCount());

        for (boolean hasItem = playListCursor.moveToFirst(); hasItem; hasItem = playListCursor
        .moveToNext()) {
            playlistName = playListCursor.getString(playListCursor
                                                    .getColumnIndex(nameKey));
            // noOfTracks = playListCursor.getInt(playListCursor
            // .getColumnIndex(tracksCountKey));
            Log.d(this.getClass().getName(), "playlistname=" + playlistName // returns only default playliststhe
                  + "tracks=" + noOfTracks);
            playlistModel.add(new Play(playlistName, noOfTracks));
        }


    }

}

All I get is a blank screen. Please guide me

回答1:

the simple way to create a playlist is :

            public void addnewPlaylist(Context context, String newplaylist) {
    ContentResolver resolver = context.getContentResolver();
    ContentValues values = new ContentValues(1);
    values.put(MediaStore.Audio.Playlists.NAME, newplaylist);
    resolver.insert(uri, values);

}

then populate the playlist:

    public void addTrackToPlaylist(Context context, String audio_id,
    long playlist_id, int pos) {
    Uri newuri = MediaStore.Audio.Playlists.Members.getContentUri(
            "external", playlist_id);
    ContentResolver resolver = context.getContentResolver();
    ContentValues values = new ContentValues();
        values.put(MediaStore.Audio.Playlists.Members.PLAY_ORDER, pos);
        values.put(MediaStore.Audio.Playlists.Members.AUDIO_ID, audio_id);
        values.put(MediaStore.Audio.Playlists.Members.PLAYLIST_ID,
                playlist_id);
        resolver.insert(newuri, values);

}

Looking at your code, you do not build the correct structure. A playlist does not hold the playlist name, simply the Playlist_id.

To return all your playlists :

        public Cursor getandroidPlaylistcursor(Context context) {
    ContentResolver resolver = context.getContentResolver();
    final String id = MediaStore.Audio.Playlists._ID;
    final String name = MediaStore.Audio.Playlists.NAME;
    final String[] columns = { id, name };
    final String criteria = null
    return  resolver.query(uri, columns, criteria, null,
            name + " ASC");

}

回答2:

Example to populate an array :

           Cursor cursor = plist.getPlaylistTracks(getActivity(), playlist_id);
     // replace with your own method to get cursor
    ArrayList<String> audio_ids = new ArrayList<String>();

    // build up the array with audio_id's
    int i = 0;
    if (cursor != null && cursor.moveToFirst()) {
        for (cursor.moveToFirst(); !cursor.isAfterLast(); cursor.moveToNext()) {
            String audio_id = cursor.getString(cursor.getColumnIndex(MediaStore.Audio.Playlists.Members.AUDIO_ID));
            audio_ids.add(audio_id);
        }

Make sure that when you assign audio_id (or your own variable) you use the correct MediaStore uri as used when you obtained the cursor. The column names in your cursor determine what you can get here.