Swift iOS - 当应用程序从后台返回时，AVPlayer 视频冻结/暂停

Question

我的应用程序登录页面上有一个循环播放的视频。我按照这个 Youtube 教程进行操作 loop video in view controller

问题是当应用程序进入后台时，如果我不立即返回，当我返回时视频会被冻结。

根据 Apple Docs 应该发生的情况。

我尝试使用 NotificationCenter 的 Notification.Name.UIApplicationWillResignActive 但没有用。

如何让视频在应用 returns 从后台继续播放后继续播放？

var player: AVPlayer!
var playerLayer: AVPlayerLayer!

override func viewDidLoad() {
        super.viewDidLoad()

        configurePlayer()
}


@objc fileprivate func configurePlayer(){

        let url = Bundle.main.url(forResource: "myVideo", withExtension: ".mov")

        player = AVPlayer.init(url: url!)
        playerLayer = AVPlayerLayer(player: player!)
        playerLayer.videoGravity = AVLayerVideoGravityResizeAspectFill
        playerLayer.frame = view.layer.frame


        player.actionAtItemEnd = AVPlayerActionAtItemEnd.none

        player.play()

        view.layer.insertSublayer(playerLayer, at: 0)

        NotificationCenter.default.addObserver(self, selector: #selector(playerItemReachedEnd), name: NSNotification.Name.AVPlayerItemDidPlayToEndTime, object: player.currentItem)

        NotificationCenter.default.addObserver(self, selector: #selector(playerItemReachedEnd), name: Notification.Name.UIApplicationWillResignActive, object: player.currentItem)

    }

@objc fileprivate func playerItemReachedEnd(){
        player.seek(to: kCMTimeZero)
    }

Answer 1

添加观察者

func addPlayerNotifications() {
    NotificationCenter.default.addObserver(self, selector: #selector(playerItemDidPlayToEnd), name: .AVPlayerItemDidPlayToEndTime, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(applicationWillEnterForeground), name: .UIApplicationWillEnterForeground, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(applicationDidEnterBackground), name: .UIApplicationDidEnterBackground, object: nil)
}

移除观察者

func removePlayerNotifations() {
    NotificationCenter.default.removeObserver(self, name: .AVPlayerItemDidPlayToEndTime, object: nil)
    NotificationCenter.default.removeObserver(self, name: .UIApplicationWillEnterForeground, object: nil)
    NotificationCenter.default.removeObserver(self, name: .UIApplicationDidEnterBackground, object: nil)
}

方法

// Player end.
@objc  func playerItemDidPlayToEnd(_ notification: Notification) {
    // Your Code.
    player.seek(to: kCMTimeZero)
}

//App enter in forground.
@objc func applicationWillEnterForeground(_ notification: Notification) {
      player.play()
}

//App enter in forground.
@objc func applicationDidEnterBackground(_ notification: Notification) {
      player.pause()
}

试试这个代码

Answer 2

根据 Apple Docs 当视频正在播放并且应用程序被发送到后台时，播放器会自动暂停：

他们说要做的是在应用程序进入后台时删除 AVPlayerLayer（设置为 nil），然后在进入前台时重新初始化它：

他们说处理这个问题的最好方法是 applicationDidEnterBackground 和 applicationDidBecomeActive:

我使用 NSNotification 来侦听背景和前景事件并设置函数以暂停播放器并将 playerLayer 设置为 nil（均用于背景事件），然后重新初始化 playerLayer 并为前景事件播放播放器。这些是我使用的通知 .UIApplicationWillEnterForeground 和 .UIApplicationDidEnterBackground

我发现，出于某种原因，如果您长按主屏幕按钮并弹出显示 "What can I help you with" 的屏幕，如果您再次按主屏幕按钮返回对于您的应用程序，视频将被冻结，并且使用上面的 2 个通知不会阻止它。我发现防止这种情况的唯一方法是也使用通知 .UIApplicationWillResignActive 和 .UIApplicationDidBecomeActive。如果除了上述通知之外您不添加这些，那么您的视频将在主页按钮长按并返回时冻结。我发现防止所有冻结情况的最佳方法是使用所有 4 个通知。

我必须做的与上面的代码不同的 2 件事是将 player 和 playerLayer class 变量设置为可选变量而不是隐式展开的可选变量，我还添加了 AVPlayer class 的扩展到检查它是否在 iOS 9 或以下版本中播放。在 iOS 10 及更高版本中有一个内置方法 .timeControlStatus AVPlayer timer status

我上面的代码：

var player: AVPlayer?
var playerLayer: AVPlayerLayer?

在 iOS 9 或更低版本中将 AVPlayer 添加到 check the state of the AVPlayer：

import AVFoundation

extension AVPlayer{

    var isPlaying: Bool{
        return rate != 0 && error == nil
    }
}

下面是完整的代码：

var player: AVPlayer?
var playerLayer: AVPlayerLayer? //must be optional because it will get set to nil on background event

override func viewDidLoad() {
    super.viewDidLoad()

    // background event
    NotificationCenter.default.addObserver(self, selector: #selector(setPlayerLayerToNil), name: UIApplication.didEnterBackgroundNotification, object: nil)

    // foreground event
    NotificationCenter.default.addObserver(self, selector: #selector(reinitializePlayerLayer), name: UIApplication.willEnterForegroundNotification, object: nil)

   // add these 2 notifications to prevent freeze on long Home button press and back
    NotificationCenter.default.addObserver(self, selector: #selector(setPlayerLayerToNil), name: UIApplication.willResignActiveNotification, object: nil)

    NotificationCenter.default.addObserver(self, selector: #selector(reinitializePlayerLayer), name: UIApplication.didBecomeActiveNotification, object: nil)

    configurePlayer()
}

override func viewWillAppear(_ animated: Bool) {
    super.viewWillAppear(animated)

    // this is also for the long Home button press
    if let player = player{
        if #available(iOS 10.0, *) {
            if player.timeControlStatus == .paused{
                player.play()
            }
        } else {
            if player.isPlaying == false{
                player.play()
            }
        }
    }
}

@objc fileprivate func configurePlayer(){

    let url = Bundle.main.url(forResource: "myVideo", withExtension: ".mov")

    player = AVPlayer.init(url: url!)
    playerLayer = AVPlayerLayer(player: player!)
    playerLayer?.videoGravity = AVLayerVideoGravityResizeAspectFill
    playerLayer?.frame = view.layer.frame

    player?.actionAtItemEnd = AVPlayerActionAtItemEnd.none

    player?.play()

    view.layer.insertSublayer(playerLayer!, at: 0)

    NotificationCenter.default.addObserver(self, selector: #selector(playerItemReachedEnd), name: NSNotification.Name.AVPlayerItemDidPlayToEndTime, object: player.currentItem)
}

@objc fileprivate func playerItemReachedEnd(){
     // this works like a rewind button. It starts the player over from the beginning
     player?.seek(to: kCMTimeZero)
}

 // background event
@objc fileprivate func setPlayerLayerToNil(){
    // first pause the player before setting the playerLayer to nil. The pause works similar to a stop button
    player?.pause()
    playerLayer = nil
}

 // foreground event
@objc fileprivate func reinitializePlayerLayer(){

    if let player = player{

        playerLayer = AVPlayerLayer(player: player)

        if #available(iOS 10.0, *) {
            if player.timeControlStatus == .paused{
                player.play()
            }
        } else {
            // if app is running on iOS 9 or lower
            if player.isPlaying == false{
                player.play()
            }
        }
    }
}

不要忘记将 isPlaying 扩展添加到 AVPlayer

Answer 3

接受的答案对我不起作用。我的 "welcome" 视频有时会随机暂停。

这是做了什么：
Background：因为当应用 "resignsActive" 或进入 "background" 时，player 和 playerLayer 对象不会被销毁（可以通过在调用各自的通知时观察它们的状态）我推测将这些对象中的任何一个设置为 nil 然后在进入背景或前景时重新初始化它们有点不必要。

我只在播放器对象进入前景时再次播放。

var player: AVPlayer?
var playerLayer: AVPlayerLayer?

在 ViewDidLoad 中，我配置我的播放器对象。

override func viewDidLoad() {
  configurePlayer()
}

configurePlayer()函数定义如下

private func configurePlayer() {
  guard let URL = Bundle.main.url(forResource: "welcome", withExtension: ".mp4") else { return }

  player = AVPlayer.init(url: URL)
  playerLayer = AVPlayerLayer(player: player)
  playerLayer?.videoGravity = AVLayerVideoGravity.resizeAspectFill
  playerLayer?.frame = view.layer.frame

  player?.actionAtItemEnd = AVPlayerActionAtItemEnd.none
  playItem()

  setupPlayNotificationItems()
}

这里是辅助函数的实现

private func setupPlayNotificationItems() {
  NotificationCenter.default.addObserver(self,
                                        selector: #selector(restartPlayerItem),
                                        name: NSNotification.Name.AVPlayerItemDidPlayToEndTime,
                                        object: player?.currentItem)
  NotificationCenter.default.addObserver(self,
                                        selector: #selector(playItem),
                                        name: .UIApplicationWillEnterForeground,
                                        object: nil)
}

@objc private func playItem() {
  // If you please, you can also restart the video here
  restartPlayerItem()

  player?.play()

  if let playerlayer = playerLayer {
    view.layer.insertSublayer(playerlayer, at: 0)
  }
}

@objc func restartPlayerItem() {
  player?.seek(to: kCMTimeZero)
}

Answer 4

我在 Swift 4.3 中找到了一个适合我的简单解决方案。我刚刚在覆盖的 ViewDidLoad 中为应用程序何时进入后台以及何时进入前台创建了一个观察者。

NotificationCenter.default.addObserver(self, selector:#selector(VideoViewController.shutItDown), name: UIApplication.didEnterBackgroundNotification, object: UIApplication.shared)
NotificationCenter.default.addObserver(self, selector:#selector(VideoViewController.refresh), name: UIApplication.willEnterForegroundNotification, object: nil)

然后我在 class 中有以下观察者调用的方法：

@objc func refresh() {
    setupVideo()
}

@objc func shutItDown() {
    self.newLayer.removeFromSuperlayer()
}

其中 newLayer 是我的 AVLayer，它作为子层添加到我的 VideoView。为了更详细一点，我已经为我的视频设置添加了代码，以确保一切都可以理解，即使你的看起来可能非常不同。

private func setupVideo() {

    self.path = URL(fileURLWithPath: Bundle.main.path(forResource: "coined", ofType: "mov")!)
    self.player = AVPlayer(url: self.path)

    self.newLayer = AVPlayerLayer(player: self.player)
    self.newLayer.frame = self.videoView.frame
    self.videoView.layer.addSublayer(newLayer)
    self.newLayer.videoGravity = AVLayerVideoGravity.resizeAspectFill

    self.player.play()

    self.videoView.bringSubviewToFront(continueButton)
    self.videoView.bringSubviewToFront(settingsButton)
}

这个方法的"drawback"就是每次从后台转到前台，视频都会重新开始播放。这在我的案例中是可以接受的，但在你的案例中可能不是这样。这是因为当你进入后台时 AVLayer 被删除，每次你进入前台时我都会在 videoView 上放置一个新的 AVLayer。删除旧的 AVLayer 是防止渲染快照错误的基础，换句话说，克服 "freeze".

Answer 5

Tsonono 的回答效果很好，我只是用它来修复卡住的视频。

一方面不要摆脱他所说的缺点（每次进入前台时视频都会重新启动），使用这两种方法时只需调用播放器本身（在关闭方法中暂停播放器并在刷新方法中播放播放器） :

@objc func refresh() {
self.player?.play()
@objc func shutItDown() {
self.player?.pause()

}

Swift iOS - 当应用程序从后台返回时，AVPlayer 视频冻结/暂停

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