如何将活动指示器设置为Web视图（yt播放器视图）并在加载完成时停止？

Question

 @IBOutlet weak var ytplayer: YTPlayerView!
 var actInd = UIActivityIndicatorView()
 override func viewDidLoad() {
    super.viewDidLoad()

    actInd.center = self.ytplayer.center
    actInd.activityIndicatorViewStyle = .gray

  ytplayer.addSubview(actInd)
  actInd.startAnimating()
  ytplayer.delegate = self
  let playerVars = ["playsinline": 1, "rel": 0  ]
    self.ytplayer.load(withVideoId: videoid, playerVars: playerVars)
}

func playerView(_ playerView: YTPlayerView, didChangeTo state: YTPlayerState) {
    switch state {
    case YTPlayerState.playing:
        DispatchQueue.main.async(){
            self.actInd.stopAnimating()
            self.actInd.hidesWhenStopped = true
        }
    default:
        print("nothing")
        break
    }

我希望在加载ytplayerview期间显示活动指示器。 并在加载完成后停止。我不知道我在哪里做错了。任何帮助表示赞赏，谢谢......