遥控器播放器未在锁定屏幕上显示

Question

我创建了一个类来处理远程控制事件的设置。所有的print语句都在函数的主体中打印，但是事件永远不会被调用。同样，元数据也永远不会显示在锁定屏幕或命令中心上。我叫UIApplication.shared.beginReceivingRemoteControlEvents()
在应用程序委托didFinishLaunching中。有人可以解释为什么没有显示数据以及为什么控件不起作用吗？音频会话也设置为.playback

RemoteControlsHelper类{

    static let instance = RemoteControlsHelper()

    var currentPodcast = Podcast()
    var player = AVAudioPlayer()

    func setupRemoteTransportControls() {
        // Get the shared MPRemoteCommandCenter

        print("setting up commands")
        let commandCenter = MPRemoteCommandCenter.shared()

        commandCenter.playCommand.isEnabled = true
        commandCenter.pauseCommand.isEnabled = true

        // Add handler for Play Command
        commandCenter.playCommand.addTarget { (event) -> MPRemoteCommandHandlerStatus in
            if self.player.rate == 0.0 {
                self.player.play()
                print("s")
                return .success
            }
            print("f")
            return .commandFailed
        }

        // Add handler for Pause Command
        commandCenter.pauseCommand.addTarget { (event) -> MPRemoteCommandHandlerStatus in
            if self.player.rate == 1.0 {
                self.player.pause()
                print("s")
                return .success
            }
            print("f")
            return .commandFailed
        }
    }

    func setupNowPlaying(img: UIImage?) {
        print("setting data")
        // Define Now Playing Info
        var nowPlayingInfo = [String : Any]()
        nowPlayingInfo[MPMediaItemPropertyTitle] = self.currentPodcast.title
        nowPlayingInfo[MPMediaItemPropertyArtist] = self.currentPodcast.author
        print(self.currentPodcast.title)

        if let image = img {
            nowPlayingInfo[MPMediaItemPropertyArtwork] =
                MPMediaItemArtwork(boundsSize: image.size) { size in
                    return image
            }
        }
        print("continuing")
        //nowPlayingInfo[MPNowPlayingInfoPropertyElapsedPlaybackTime] = self.player.currentTime
        //nowPlayingInfo[MPMediaItemPropertyPlaybackDuration] = self.player.duration
        //nowPlayingInfo[MPNowPlayingInfoPropertyPlaybackRate] = self.player.rate

        // Set the metadata
        MPNowPlayingInfoCenter.default().nowPlayingInfo = nowPlayingInfo
    }

    @objc func toggleAudio() {
        if self.player.isPlaying {
            self.player.pause()
        } else {
            self.player.play()
        }
    }
}