1. 首先，需要在 AVPlayer 的初始化过程中添加一个属性，以确保视频缓存缓存大小足够大。

let playerItem = AVPlayerItem(url: videoURL)
playerItem.preferredForwardBufferDuration = 5
let player = AVPlayer(playerItem: playerItem)

2. 在 UISlider 正在拖拽/松开拖拽的事件中，获取当前滑块的值，并将其应用到 AVPlayer 对象的 seek 方法中。此外，您还需要将内置的视频控制器替换为自定义控制器。

class CustomSlider: UISlider {

    var seekCallback: (() -> Void)?

    override func endTracking(_ touch: UITouch?, with event: UIEvent?) {
        super.endTracking(touch, with: event)
        seekCallback?()
    }
}

class ViewController: UIViewController {

    @IBOutlet weak var slider: CustomSlider!

    override func viewDidLoad() {
        super.viewDidLoad()

        let videoURL = URL(string: "https://myremoteserver.com/myvideo.mp4")!
        let playerItem = AVPlayerItem(url: videoURL)
        playerItem.preferredForwardBufferDuration = 5
        let player = AVPlayer(playerItem: playerItem)

        let playerLayer = AVPlayerLayer(player: player)
        playerLayer.frame = view.bounds
        view.layer.addSublayer(playerLayer)

        // 监听 seek 完成的事件
        slider.seekCallback = {
            let destTime = CMTimeMakeWithSeconds(Double(self.slider.value), preferredTimescale: 1)
            player.seek(to: destTime)
        }
    }
}

3. 最后，您还需要在 AVPlayer 中添加缓存观察器，以确保视频的平滑播放。

let videoURL = URL(string: "https://myremoteserver.com/myvideo.mp4")!
let playerItem = AVPlayerItem(url: videoURL)
playerItem.preferredForwardBufferDuration = 5
let player = AVPlayer(playerItem: playerItem)

let playerLayer = AVPlayer