使用 UIPanGestureRecognizer 向下滑动 UIView

Question

我的 UIView 中有一个 UIPanGestureRecognizer 的 IBAction，我能够处理手势并识别状态从开始、取消和结束的变化，以及响应这些变化。

然而，当使用 sender.location 处理向下滑动时，UIView 实际上在手势开始后向上移动，然后继续向下移动。这种体验令人震惊，我不确定自己做错了什么。有人有什么想法吗？

func update(_ translation: CGPoint, origin: CGPoint) {

    let offSetY = translation.y

    cardView.frame.origin.y = offSetY

    let multiplier = 1 - (translation.y / 2000)
    self.view.alpha = multiplier
}


func cancel(_ origin: CGPoint) {

    let animator = UIViewPropertyAnimator(duration: 0.6, dampingRatio: 0.6) {
        self.visualEffectView.alpha = 1
        self.cardView.alpha = 1.0
        self.view.alpha = 1.0
        self.cardView.center = origin
    }
    animator.startAnimation()
}

func finish() {
    let animator = UIViewPropertyAnimator(duration: 0.9, dampingRatio: 0.9) {
        self.visualEffectView.effect = nil
        self.dismiss(animated: true, completion: nil)
    }
    animator.startAnimation()
}



@IBAction func panGestureAction(_ sender: UIPanGestureRecognizer) {

    self.view.backgroundColor = .white
    let originalCardPosition = cardView.center

   //let cardOriginY = cardView.frame.origin.y
    let translation = sender.translation(in: self.cardView)
    let origin = sender.location(in: self.cardView)

        switch sender.state {
        case .changed:


            if translation.y > 0 { update(translation, origin: origin) }

        case .ended:

            let translation = sender.translation(in: self.cardView)

            if translation.y > 100 {

                finish()

            } else {
                cardView.alpha = 1.0
                cancel(originalCardPosition)

            }
        case .cancelled:
            cancel(originalCardPosition)

        default: break
        }

}

Answer 1

问题是你把cardView的origin.y直接设置成了translation.y的值。您需要将 translation.y 添加到手势开始时确定的视图原始 y 值。

在class中添加一个属性:

var originalY: CGFloat = 0

然后在手势的.began状态下，设置：

originalY = cardView.frame.origin.y

然后在您的 update 方法中设置原点：

cardView.frame.origin.y = originalY + offSetY

使用 UIPanGestureRecognizer 向下滑动 UIView

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