     }
   }
 
-  func nextTrack() {
+  @objc func nextTrack() {
     guard let urls = urls else { return }
     selected = min(selected + 1, urls.count - 1)
     play(url: urls[selected])
   }
 
-  func previousTrack() {
+  @objc func previousTrack() {
     guard let urls = urls else { return }
     selected = max(selected - 1, 0)
     play(url: urls[selected])


    playButton.setImage(#imageLiteral(resourceName: "PlayButton"), for: .normal)
    playButton.sizeToFit()
    playButton.addTarget(self, action: #selector(play as (Void) -> Void), for: .touchUpInside)
    addSubview(playButton)

    playButton.translatesAutoresizingMaskIntoConstraints = false

    mpic.nowPlayingInfo?[MPNowPlayingInfoPropertyElapsedPlaybackTime] = audioPlayer.currentTime().seconds
  }

  @objc func progressBarTapped(recognizer: UITapGestureRecognizer) {
    guard let view = recognizer.view else { return }

    let pt = recognizer.location(in: view)
