在2个固定点之间滑动UIView

Question

我试图让UIView幻灯片在2点之间滑动。 我尝试使用UIPanGestureRecognizer。 滑动很好，但是当视图到达极限点时，会有颠簸的跳动。 这不顺利。 这是我的手势功能：

    func wasDragged(gestureRecognizer: UIPanGestureRecognizer) {
    if gestureRecognizer.state == UIGestureRecognizerState.began || gestureRecognizer.state == UIGestureRecognizerState.changed {
        let translation = gestureRecognizer.translation(in: self.view)
        print(gestureRecognizer.view!.center.x)
        if(gestureRecognizer.view!.center.x <= self.view.frame.width) && (gestureRecognizer.view!.center.x >= self.view.frame.width - 100) {
            gestureRecognizer.view!.center = CGPoint(x: gestureRecognizer.view!.center.x + translation.x, y:  gestureRecognizer.view!.center.y)
        }else if (gestureRecognizer.view!.center.x > self.view.frame.width){
            gestureRecognizer.view!.center = CGPoint(x: self.view.frame.width, y: gestureRecognizer.view!.center.y)
        }else if (gestureRecognizer.view!.center.x < self.view.frame.width - 100){
            gestureRecognizer.view!.center = CGPoint(x: self.view.frame.width - 100, y: gestureRecognizer.view!.center.y)
        }

        gestureRecognizer.setTranslation(CGPoint(x: 0,y: 0), in: self.view)
    }


}

有什么帮助吗？ 谢谢。

Answer 1

您的问题是您正在查看视图的当前位置，而不是在应用当前移动后的视图位置。

我通过引入newx修复了您的代码，其中newx显示了视图试图移动到的位置。 那就是您要限制的值。

@IBAction func wasDragged(gestureRecognizer: UIPanGestureRecognizer) {
    if gestureRecognizer.state == .began || gestureRecognizer.state == .changed {
        let translation = gestureRecognizer.translation(in: self.view)
        print(gestureRecognizer.view!.center.x)
        let newx = gestureRecognizer.view!.center.x + translation.x

        if(newx <= self.view.frame.width) && (newx >= self.view.frame.width - 100) {
            gestureRecognizer.view!.center = CGPoint(x: newx, y:  gestureRecognizer.view!.center.y)
        }else if (newx > self.view.frame.width){
            gestureRecognizer.view!.center = CGPoint(x: self.view.frame.width, y: gestureRecognizer.view!.center.y)
        }else if (newx < self.view.frame.width - 100){
            gestureRecognizer.view!.center = CGPoint(x: self.view.frame.width - 100, y: gestureRecognizer.view!.center.y)
        }

        gestureRecognizer.setTranslation(CGPoint(x: 0,y: 0), in: self.view)
    }
}

---

您可能还想考虑对最终setTranslation调用的更改。 如果用户试图在视图已达到其左极限时向左拖动，然后（不松开手指）改变方向并向右移动，即使他们的手指不再在视图上，您​​的代码也会将视图向右移动。

进行以下更改后，视图将不会向右移动，直到用户的手指回到原始触摸点为止：

gestureRecognizer.setTranslation(CGPoint(x: newx - gestureRecognizer.view!.center.x ,y: 0), in: self.view)

试试看，看看你喜欢哪个。