如何识别 AVPlayer 处于暂停状态和用户进行擦洗

Question

您好，我正在开发包含本地视频流的应用程序。当用户处于暂停状态时，我正在搜索回调或通知。我已经为 AVPlayer 添加了如下观察者：

[self.avPlayerController.player addObserver:self forKeyPath:@"status" options:0 context:NULL];
[self.avPlayerController.player addObserver:self forKeyPath:@"rate" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionInitial | NSKeyValueObservingOptionOld context:NULL];

但是当播放器暂停和用户擦洗时，观察者不会被调用。我只想检测用户何时完成擦洗或用户何时触摸进度条。任何帮助将不胜感激。谢谢。

Answer 1

观察 rate 和 status 应该可以工作 - 在我的代码中调用观察回调，因此我认为它们也适用于您。我想问题是他们只有在视频暂停时才被调用，而不是在用户擦掉它时。所以我会回答这个问题。

您可能想要观察的是currentTime。我自己尝试过，当我尝试观察AVPlayer 或其currentItem 时，也不需要KVO。我做了一些研究，似乎这根本行不通（见this SO question）。你必须找到另一种方法来做到这一点。一种方法是添加一个计时器并定期检查它的状态。结合观察rate 或timeControlStatus (see this answer)，即使视频暂停，您也应该能够知道用户正在更改 currentTime。

我希望你不介意阅读 Swift 代码，这是第一种方法：

class ViewController: UIViewController {

    let player = AVPlayerViewController()
    var timer: Timer? = nil
    var previousTime: Double = 0
    var stopped = false

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

        present(player, animated: true, completion: {
            self.player.player = AVPlayer(url: URL(string: "https://clips.vorwaerts-gmbh.de/big_buck_bunny.mp4")!)
            self.player.player?.play()
            self.player.player?.addObserver(self, forKeyPath: "rate", options: .new, context: nil)
            self.timer = Timer.scheduledTimer(withTimeInterval: 0.1, repeats: true, block: { (timer) in
                let currentTime = self.player.player?.currentTime().seconds ?? 0
                if self.previousTime != currentTime && self.stopped {
                    print(">>> User scrubbing")
                }
                self.previousTime = currentTime
            })
        })
    }

    override func observeValue(forKeyPath keyPath: String?, of object: Any?, change: [NSKeyValueChangeKey : Any]?, context: UnsafeMutableRawPointer?) {
        if keyPath == "rate" && (change?[NSKeyValueChangeKey.newKey] as? Float) == 0 {
            print(">>> stopped")
            stopped = true
        } else if keyPath == "rate" && (change?[NSKeyValueChangeKey.newKey] as? Float) == 1 {
            print(">>> played again")
            stopped = false
        }
    }
}

第二种我更喜欢的方法是继承 AVPlayer 并覆盖其 seek(to:toleranceBefore:toleranceAfter:completionHandler:) 方法。当用户擦洗视频时，AVPlayerViewController 会调用此方法 - 因此此时您可以判断用户正在擦洗（尽管在播放视频时用户擦洗它也会调用它，因此可能还需要测试是否正在播放）。

class CustomAVPlayer: AVPlayer {
    override func seek(to time: CMTime, toleranceBefore: CMTime, toleranceAfter: CMTime, completionHandler: @escaping (Bool) -> Void) {
        super.seek(to: time, toleranceBefore: toleranceBefore, toleranceAfter: toleranceAfter, completionHandler: completionHandler)

        // if you don't call this method directly, it's called only by the
        // AVPlayerViewController's slider during scrubbing
        print(">> user scrubbing")
    }
}