MPNowPlayingFoCenter在iOS 8中不显示媒体信息

我尝试使用此代码在Lockscreen和Control center中显示媒体信息，但它没有显示任何内容：

Class playingInfoCenter = NSClassFromString(@"MPNowPlayingInfoCenter");

if (playingInfoCenter) {


    NSMutableDictionary *songInfo = [[NSMutableDictionary alloc] init];


    MPMediaItemArtwork *albumArt = [[MPMediaItemArtwork alloc] initWithImage: [UIImage imagedNamed:@"AlbumArt"]];

    [songInfo setObject:@"Audio Title" forKey:MPMediaItemPropertyTitle];
    [songInfo setObject:@"Audio Author" forKey:MPMediaItemPropertyArtist];
    [songInfo setObject:@"Audio Album" forKey:MPMediaItemPropertyAlbumTitle];
    [songInfo setObject:albumArt forKey:MPMediaItemPropertyArtwork];
    [[MPNowPlayingInfoCenter defaultCenter] setNowPlayingInfo:songInfo];

}

我还设置了

FirstResponding

，但仍然没有看到任何内容

- (void) viewDidAppear: (BOOL) animated
{
    [super viewDidAppear:animated];
    [self becomeFirstResponder];
    NSLog(@"is first resp: %i",[self isFirstResponder]);

    [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];
    // Initialize the AVAudioSession here.

    [[UIApplication sharedApplication] endReceivingRemoteControlEvents];

}

- (BOOL) canBecomeFirstResponder
{
    return YES;
}

我怎样才能解决这个问题？谢谢

您是否已激活如下所示的“音频、播放和画中画”功能