Swift observevalueforkeypath + loadedTimeRanges 只调用有限的时间

Question

我正在尝试使用 AVPlayer 创建一个视频播放器。从 youtube 加载视频。我希望当视频当前时间发生变化时，我的 uiSlider 和我的时间标签可以更新。我正在使用“observeValueForKeyPath”方法从播放器项目中捕获“loadedTimeRanges”状态。这是我的代码:

override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
        print("keyPath: \(keyPath)")
        let playerItem:AVPlayerItem = object as! AVPlayerItem
        if keyPath == "status" {
            if playerItem.status ==  AVPlayerItemStatus.ReadyToPlay{
                print("AVPlayerItemStatusReadyToPlay")
            } else if playerItem.status == AVPlayerItemStatus.Failed {
                print("AVPlayerItemStatusFailed")
            }
        } else if keyPath == "loadedTimeRanges" {
            let currentTime = playerItem.currentTime().seconds
            let totalDuration = playerItem.duration.seconds
            print("value: \(Float(currentTime/totalDuration))")
            self.monitoringPlayback(player.currentItem!)
            self.slider.setValue(Float(currentTime/totalDuration), animated: false)
        }
    }

    func monitoringPlayback(playerItem:AVPlayerItem) {
        let currentSecond:Double = playerItem.currentTime().seconds
        self.updateVideoSlider(currentSecond)
        let timeString = self.updateTime(playerItem.duration.seconds - currentSecond)
        print("time string: \(timeString)")
        self.lblTime.text = timeString
    }

但是，“observeValueForKeyPath”方法每次只调用 20-22 次。请检查日志截图:https://gyazo.com/5ca57ba532689d83aea855ae41387f53这是我第一次使用这种方法，所以可能我不明白它是如何工作的。如果有人知道，请告诉我为什么。感谢您阅读我的问题。

Answer 1

很简单

var rightCurrentTimer: UILabel = {

    let lbl = UILabel()
    lbl.text = "00:00"
    lbl.textColor = .white
    lbl.translatesAutoresizingMaskIntoConstraints = false
    lbl.font = UIFont.systemFont(ofSize: 11)
    return lbl

}()

let leftWhatTimePlayed:UILabel = {

    let lbl = UILabel()
    lbl.translatesAutoresizingMaskIntoConstraints = false
    lbl.textColor = .white
    lbl.text = "00:00"
    lbl.font = UIFont.systemFont(ofSize: 11)
    return lbl

}()

让间隔= CMTime(值:1，时间刻度:1)

    player?.addPeriodicTimeObserver(forInterval: interval, queue: DispatchQueue.main, using: { (timeProgress) in

        let secondsPlay = CMTimeGetSeconds(timeProgress)
        let secondString = String(format:"%02d" , Int(secondsPlay) % 60 )
        let minutesString = String(format:"%02d", Int(secondsPlay) / 60)

        self.leftWhatTimePlayed.text = "\(minutesString):\(secondString)"

        if let duration = self.player?.currentItem?.duration {

            let totalSecond = CMTimeGetSeconds(duration)

            let whatSecondIsPlay = totalSecond - secondsPlay

            let secondsIsPlay = String(format:"%02d" , Int(whatSecondIsPlay) % 60)
            let minutesIsPlay = String(format: "%02d", Int(whatSecondIsPlay) / 60)

            self.rightCurrentTimer.text = "\(minutesIsPlay):\(secondsIsPlay)"
            self.videoLengthTimeSlider.value = Float(secondsPlay/totalSecond)

        }


    })