Swift:暂停正在沿路径移动的动画？

import UIKit

class ViewController: UIViewController {
    var animationLayer: CALayer!
    var isAnimating: Bool = true

    override func viewDidLoad() {
        super.viewDidLoad()

        // 创建一个CALayer并添加到UIView中
        animationLayer = CALayer()
        animationLayer.bounds = CGRect(x: 0, y: 0, width: 50, height: 50)
        animationLayer.position = CGPoint(x: 50, y: 50)
        animationLayer.backgroundColor = UIColor.red.cgColor
        view.layer.addSublayer(animationLayer)

        // 创建沿路径移动的动画
        let animation = CAKeyframeAnimation(keyPath: "position")
        animation.path = UIBezierPath(rect: CGRect(x: 0, y: 0, width: 200, height: 200)).cgPath
        animation.duration = 5
        animation.repeatCount = Float.infinity
        animationLayer.add(animation, forKey: "pathAnimation")

        // 暂停动画
        pauseAnimation()
    }

    func pauseAnimation() {
        if isAnimating {
            // 暂停动画
            animationLayer.speed = 0
            // 保存当前动画的时间点
            animationLayer.timeOffset = animationLayer.convertTime(CACurrentMediaTime(), from: nil)
            isAnimating = false
        }
    }

    func resumeAnimation() {
        if !isAnimating {
            // 恢复动画
            animationLayer.speed = 1
            // 计算暂停期间的时间偏移
            let pauseTime = animationLayer.timeOffset
            let timeSincePause = animationLayer.convertTime(CACurrentMediaTime(), from: nil) - pauseTime
            // 更新动画的开始时间
            animationLayer.beginTime = timeSincePause
            // 清除时间偏移
            animationLayer.timeOffset = 0
            isAnimating = true
        }
    }

    override func touchesBegan(_ touches: Set<UITouch>, with event: UIEvent?) {
        // 点击屏幕时切换动画的播放状态
        if isAnimating {
            pauseAnimation()
        } else {
            resumeAnimation()
        }
    }
}