Avplayer并不总是播放完整的视频

Question

AVPlayer有时会在播放视频时重新开始，我不知道为什么。此外，只要加载视图，它就会开始播放。我希望用户先点击播放，然后让播放器开始播放。

这是我的代码：

class VideoPreviewViewController: UIViewController {

// 1
static let assetKeysRequiredToPlay = ["playable","hasProtectedContent"]
// 2
let player = AVPlayer()

// 3
var asset:AVURLAsset? {
    // 9
    didSet {
        guard let newAsset = asset else { return }
        loadURLAsset(newAsset)
    }
}

// 4
var playerLayer:AVPlayerLayer? {
    return playerView.playerLayer
}

// 5
var playerItem:AVPlayerItem? {
    didSet {
        player.replaceCurrentItem(with: self.playerItem)
        player.actionAtItemEnd = .none
    }
}

// 6
var fileLocation:URL? {
    // 10
    didSet {
        self.asset = AVURLAsset(url: self.fileLocation!)
    }
}

@IBOutlet weak var playerView:PlayerView!
@IBOutlet weak var saveButton:UIButton!
@IBOutlet weak var playPauseButton:UIButton!

override func viewDidLoad() {
    super.viewDidLoad()

    // Do any additional setup after loading the view.

    // 11
    addObserver(self, forKeyPath: "player.currentItem.status", options: .new, context: nil)
    addObserver(self, forKeyPath: "player.rate", options: [.new, .initial], context: nil)

    // 14
    NotificationCenter.default.addObserver(self, selector: #selector(playerReachedEnd(notification:)), name: NSNotification.Name.AVPlayerItemDidPlayToEndTime, object: nil)

    // 7
    self.playerView.playerLayer.player = player
}

// 13
override func viewWillDisappear(_ animated: Bool) {
    removeObserver(self, forKeyPath: "player.currentItem.status", context: nil)
    removeObserver(self, forKeyPath: "player.rate", context: nil)
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
    // Dispose of any resources that can be recreated.
}

// MARK: Main

// 8
func loadURLAsset(_ asset: AVURLAsset) {

    asset.loadValuesAsynchronously(forKeys: VideoPreviewViewController.assetKeysRequiredToPlay) {
        DispatchQueue.main.async {
            guard asset == self.asset else { return }
            for key in VideoPreviewViewController.assetKeysRequiredToPlay {
                var error: NSError?

                if !asset.isPlayable || asset.hasProtectedContent {
                    let message = "Video is not playable."
                    self.showAlert(title: "Error", message: message, dismiss: false)
                    return
                }

                if asset.statusOfValue(forKey: key, error: &error) == .failed {

                    let message = "Failed to load"
                    self.showAlert(title: "Error", message: message, dismiss: false)


                    return
                }
            }

            self.playerItem = AVPlayerItem(asset: asset)
        }
    }
}




// MARK: Actions
@IBAction func closePreview() {
    self.dismiss(animated: true, completion: nil)
}

@IBAction func saveToLibrary() {
    // 18
    self.saveVideoToUserLibrary()
}

@IBAction func playPauseButtonPressed() {
    // 17
    self.updatePlayPauseButtonTitle()
}

// MARK: Callbacks

// 12
override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
    if keyPath == "player.currentItem.status" {
        //Do something
        playPauseButton.isHidden = false
        saveButton.isHidden = false

    }
}

// 15
func playerReachedEnd(notification:NSNotification) {
    //To restart video
    self.asset = AVURLAsset(url: self.fileLocation!)
    self.updatePlayPauseButtonTitle()
}


// MARK: Helpers
func saveVideoToUserLibrary(){
    PhotoManager().saveVideoToUserLibrary(fileUrl: self.fileLocation!) { (success, error) in
        if success {
            self.showAlert(title: "Success", message: "Video saved.", dismiss: true)
        } else {
            self.showAlert(title: "Error", message: (error?.localizedDescription)!, dismiss: false)
        }
    }
}

func showAlert(title:String, message:String, dismiss:Bool) {
    let controller = UIAlertController(title: title, message: message, preferredStyle: .alert)

    if dismiss {
        controller.addAction(UIAlertAction(title: "OK", style: .default, handler: { (action) in
            self.dismiss(animated: true, completion: nil)
        }))
    } else {
        controller.addAction(UIAlertAction(title: "OK", style: .default, handler: nil))
    }

    self.present(controller, animated: true, completion: nil)
}

// 16
func updatePlayPauseButtonTitle() {
    if player.rate > 0 {
        player.pause()
        playPauseButton.setTitle("Play", for: .normal)
    } else {
        player.play()
        playPauseButton.setTitle("Pause", for: .normal)
    }
}