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我正在设置propertyAnimator?.fractionComplete根据平移手势的翻译来更改视图的位置。稍后，我打算CGPoint.zero在手指抬起后将其动画化。这是我的代码：

Dragging the square with the cursor

class ViewController: UIViewController {
    
    let squareContainerView = UIView(frame: CGRect(x: 100, y: 70, width: 230, height: 30))
    let squareView = UIView(frame: CGRect(x: 0, y: 0, width: 30, height: 30))
    let targetSquareViewOrigin = CGFloat(200)
    let label = UILabel(frame: CGRect(x: 25, y: 140, width: 350, height: 30))
    
    var propertyAnimator: UIViewPropertyAnimator?
    
    var panGesture: UIPanGestureRecognizer!
    var totalTranslation = CGFloat(0) {
        didSet {
            label.text = "Translation: \(totalTranslation.rounded()), percentage: \(totalTranslation / squareContainerView.frame.width)"
        }
    }
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        view.addSubview(squareContainerView)
        squareContainerView.addSubview(squareView)
        view.addSubview(label)
        
        squareContainerView.backgroundColor = UIColor.red
        squareView.backgroundColor = UIColor.blue
        label.text = "Translation: \(totalTranslation.rounded()), percentage: \(totalTranslation / squareContainerView.frame.width)"
        
        panGesture = UIPanGestureRecognizer(target: self, action:(#selector(self.handleGesture(_:))))
        squareContainerView.addGestureRecognizer(panGesture)
        
        propertyAnimator = UIViewPropertyAnimator(duration: 1, curve: .linear)
        propertyAnimator?.addAnimations {
            self.squareView.frame.origin.x = self.targetSquareViewOrigin
        }
    }
    
    @objc func handleGesture(_ sender: UIPanGestureRecognizer) {

        totalTranslation += sender.translation(in: squareContainerView).x
        let fractionComplete = totalTranslation / squareContainerView.frame.width
        propertyAnimator?.fractionComplete = fractionComplete
        
        sender.setTranslation(.zero, in: squareContainerView) /// reset to zero
    }
}

方形视图正在移动，但是当百分比高于1或低于0时，它会停止。这是有道理的，因为它的原始来源是CGPoint.zero，我用addAnimations().

但是，我希望它继续移动，即使分数完成了。在文档中它说：

定义自定义动画器时，如果您支持动画运行超过其起点或终点，则可以允许大于 1.0 或小于 0.0 的值。

我该如何启用它？我应该创建一个子类，如果是，我应该重写哪些方法？

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