如何让AVPlayerLayer铺满UIView并实现视频循环播放？

你的代码仅设置了AVPlayerLayer的初始尺寸，未处理视图布局变化的场景，且尺寸设置方式不够稳妥，导致无法始终铺满videoView。可以通过以下两步调整：

1. 保存AVPlayerLayer引用并正确设置初始尺寸 #

先在类中添加AVPlayerLayer类型的属性，方便后续更新尺寸；然后直接将图层的frame设为videoView的bounds，替代原分开设置bounds和position的方式：

// 在类顶部添加属性
var player: AVPlayer?
var playerLayer: AVPlayerLayer? // 新增该属性

func playVideo(videoString: String) {
    guard let videoURL = URL(string: videoString) else { return }
    
    self.player = AVPlayer(url: videoURL)
    self.player?.isMuted = true
    self.player?.actionAtItemEnd = .none

    self.playerLayer = AVPlayerLayer(player: player)
    self.playerLayer?.videoGravity = .resizeAspectFill
    self.playerLayer?.frame = self.videoView.bounds // 直接绑定videoView的bounds
    
    self.videoView.layer.addSublayer(playerLayer!)

    self.player?.play()

    NotificationCenter.default.addObserver(self, selector: #selector(playerItemDidReachEnd), name: .AVPlayerItemDidPlayToEndTime, object: self.player?.currentItem)
}

@objc func playerItemDidReachEnd(notification: NSNotification) {
    self.player?.seek(to: .zero)
    self.player?.play()
}

2. 监听视图布局变化，动态更新图层尺寸 #

当videoView尺寸变化（比如屏幕旋转、父视图布局更新）时，同步更新playerLayer的尺寸。如果是在ViewController中，重写viewDidLayoutSubviews方法：

override func viewDidLayoutSubviews() {
    super.viewDidLayoutSubviews()
    // 每次布局更新时，让playerLayer的frame与videoView的bounds保持一致
    self.playerLayer?.frame = self.videoView.bounds
}

如果videoView是自定义UIView，可在自定义类中重写layoutSubviews：

class CustomVideoView: UIView {
    override func layoutSubviews() {
        super.layoutSubviews()
        // 找到子图层中的AVPlayerLayer并更新frame
        if let playerLayer = layer.sublayers?.first(where: { $0 is AVPlayerLayer }) as? AVPlayerLayer {
            playerLayer.frame = bounds
        }
    }
}

调整后，AVPlayerLayer就能始终铺满整个videoView。其中resizeAspectFill会让视频填满视图，超出部分会被裁剪；若需视频完整显示不裁剪，可改用.resizeAspect。

内容的提问来源于stack exchange，提问作者Telha Wasim