在播放列表中跳过曲目时，MPNowPlayingInfoCenter无法更新标题

Question

我正在尝试使用MPNowPlayingInfoCenter更新标题。但是当我跳过轨道时，它不能在控制面板上反映它。

这是我的代码：

int newIndex = [(NSNumber *)(notification.userInfo)[DRNewTrackIndex] intValue];
    NSUInteger trackCount;
    if (self.station.sortOptionType == DRFilterPlaylistSortOptionTypeShuffle) {
        trackCount = _station.playlist.tracks.count;
    } else {
        trackCount = _station.playlist.filteredTracks.count;
    }
    if (newIndex >= 0 && newIndex < trackCount) {
        DRPlaylistTrackModel *track = (self.station.sortOptionType == DRFilterPlaylistSortOptionTypeShuffle)?(_station.playlist.tracks)[newIndex]:(_station.playlist.filteredTracks)[newIndex];

        NSDictionary *nowPlayingInfoDictionary = [MPNowPlayingInfoCenter defaultCenter].nowPlayingInfo;
        NSMutableDictionary *songInfo = [[NSMutableDictionary alloc] initWithDictionary:nowPlayingInfoDictionary];

        DRDDLogVerbose(@"Setting nowPlayingInfo: (songName: %@, bandName: %@, albumName: %@)",
                       track.title, track.artist.name, track.album.name);

        NSString *title = [self titleForTrack:track];
        if (title.length > 0) {
            songInfo[MPMediaItemPropertyTitle] = title;
        }

        NSString *subTitle = [self subTitleForTrack:track];
        if (subTitle.length > 0) {
            songInfo[MPMediaItemPropertyAlbumTitle] = subTitle;
        }

        if (title.length > 0 || subTitle.length > 0) {
            [[MPNowPlayingInfoCenter defaultCenter] setNowPlayingInfo:[songInfo copy]];
        } else {
            // if title and station name are both empty, clear out old info
            [[MPNowPlayingInfoCenter defaultCenter] setNowPlayingInfo:nil];
        }
    } else {
        // clear old info
        [[MPNowPlayingInfoCenter defaultCenter] setNowPlayingInfo:nil];
    }

此外，当我将调试点放在标题和副标题附近时，我可以看到为下一首歌曲显示的正确信息。但是当我在手机上看到它时，它没有显示正确的跟踪信息，如调试点所示。 我不知道这里发生了什么。 我也保证上述内容仅在主线程上发生。