iPad上的影片播放器

import AVFoundation
import AVKit
import UIKit

class ViewController: UIViewController {
  @IBOutlet weak var lyricsLabel: UILabel!
  @IBOutlet weak var videoView: UIView!

  var player: AVPlayer?
  var timer: Timer?
  var counter = 0.0
  var isPlaying = false

  override func viewDidLoad() {
    super.viewDidLoad()

    // listen to active and resign notifications
    // ref: https://stackoverflow.com/a/45955660
    NotificationCenter.default.addObserver(self, selector: #selector(self.openAndCloseActivity),
                                           name: UIApplication.didBecomeActiveNotification, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(self.openAndCloseActivity),
                                           name: UIApplication.willResignActiveNotification, object: nil)

    // listen to end play notification
    // ref: https://www.tutorialspoint.com/how-to-use-swift-to-detect-when-avplayer-video-ends-playing
    NotificationCenter.default.addObserver(self, selector: #selector(self.videoDidEnd),
                                           name: NSNotification.Name.AVPlayerItemDidPlayToEndTime, object: nil)

    // setup avplayer controller
    initVideoView()

  }

  // setup avplayer controller
  //
  // add avplayer controller to the current view and hide playback controls
  private func initVideoView() {
    // ref: https://medium.com/@nabilsafatli/how-to-create-a-custom-control-for-avplayer-1e53b9188ae3
    guard let url = Bundle.main.url(forResource: "night", withExtension: "mp4") else { return }

    self.player = AVPlayer(url: url)
    //player!.rate = 1 //auto play
    let playerFrame = CGRect(x: 0, y: 0, width: videoView.frame.width, height: videoView.frame.height)
    let playerViewController = AVPlayerViewController()
    playerViewController.player = self.player
    playerViewController.view.frame = playerFrame

    addChild(playerViewController) // add player controller to view controller
    videoView.addSubview(playerViewController.view)
    playerViewController.didMove(toParent: self)

    playerViewController.showsPlaybackControls = false // hide playback controls
  }

  // handle play click event
  @IBAction func playVideo(_ sender: UIButton) {
    if !self.isPlaying {

      self.isPlaying = true // set flag
      self.counter = 0.0 // init counter
      self.player?.seek(to: CMTime(value: CMTimeValue(0.0), timescale: 1000)) // seek to head

      // init timer.
      // ref: https://medium.com/彼得潘的-swift-ios-app-開發教室/透過-timer-設定每幾秒重複執行-function-3c80f449107
      self.timer = Timer.scheduledTimer(
        timeInterval: 0.1,
        target: self,
        selector: #selector(updateLyrics),
        userInfo: nil,
        repeats: true)

      // play video
      self.player?.play()
    } else {
      print("already playing, do nothing...")
    }
  }

  @objc func updateLyrics() {
    self.counter += 0.1 // increase counter

    switch self.counter {
    case 5.0...20.0:
      self.lyricsLabel.text = "IU - 夜信" // 0
    case 24.4...37.4:
      self.lyricsLabel.text = "今晚  我想將那天的螢火" // 1
    case 37.5...47.0:
      self.lyricsLabel.text = "送到你的窗前" // 2
    case 49.6...59.0:
      self.lyricsLabel.text = "含意是 \"我愛你\"" // 3
    case 68.8...80.8:
      self.lyricsLabel.text = "我想起我們的初吻" // 4
    case 80.9...90.0:
      self.lyricsLabel.text = "不管何時 只要閉上雙眼" // 5
    case 93.1...103.2:
      self.lyricsLabel.text = "就能奔向那最遙遠的地方" // 6
    case 105.7...115.8:
      self.lyricsLabel.text = "就像我在被浪濤湧來的沙上寫下的字跡般" // 7,8
    case 115.9...123.4:
      self.lyricsLabel.text = "你感覺也會像他們那樣從此消失" // 9
    case 123.5...127.4:
      self.lyricsLabel.text = "總是想念" // 10
    case 127.5...141.0:
      self.lyricsLabel.text = "雖然無法將我心裡所有的話語  說給你聽" // 11,12
    case 141.2...151.3:
      self.lyricsLabel.text = "但那裡頭全都是 \"我愛你\"" // 13
    case 160.1...166.0:
      self.lyricsLabel.text = "我何德何能" // 14
    case 166.1...171.7:
      self.lyricsLabel.text = "能擁有名為你的這份幸運" // 15
    case 171.8...176.8:
      self.lyricsLabel.text = "若我們現在能望著對方" // 16
    case 176.9...184.0:
      self.lyricsLabel.text = "該有多美好" // 17
    case 184.1...194.1:
      self.lyricsLabel.text = "就像我在被浪濤湧來的沙上寫下的字跡般" // 18,19
    case 194.2...202.5:
      self.lyricsLabel.text = "你感覺也會像他們那樣從此消失" // 20
    case 202.6...205.8:
      self.lyricsLabel.text = "還是想念" // 21
    case 205.9...212.1:
      self.lyricsLabel.text = "雖然無法將我寫在日記上的一字一句" // 22
    case 212.2...220.5:
      self.lyricsLabel.text = "都告訴你" // 23
    case 220.6...226.4:
      self.lyricsLabel.text = "但字字句句都代表著我愛你" // 24
    case 228.5...241.9:
      self.lyricsLabel.text = "今晚  我想將那天的螢火" // 25
    case 242.0...249.7:
      self.lyricsLabel.text = "送到你的窗前" // 26
    case 255.9...267.2:
      self.lyricsLabel.text = "希望今夜的你有個美好的夢" // 27
    default:
      self.lyricsLabel.text = ""
    }
  }

  // handle vidie end notification
  // ref: https://www.tutorialspoint.com/how-to-use-swift-to-detect-when-avplayer-video-ends-playing
  @objc func videoDidEnd(notification: NSNotification) {
    print("video ended")
    self.timer?.invalidate() // stop timer
    self.isPlaying = false
    self.lyricsLabel.text = ""
  }

  // handle activity resume and close
  // ref: https://stackoverflow.com/a/45955660
  @objc func openAndCloseActivity(_ notification: Notification)  {
    if notification.name == UIApplication.didBecomeActiveNotification{
      print("resume activity")

      // seek to head
      self.player?.seek(to: CMTime(value: CMTimeValue(0.0), timescale: 1000)) // ref: https://stackoverflow.com/a/59839041
    } else{
      print("close activity")

      self.player?.pause() // pause player
      self.timer?.invalidate() // stop timer
      self.isPlaying = false
      self.lyricsLabel.text = ""
    }
  }
}