使用 UIPanGestureRecognizer 获取视图的翻译 - 快速 - 以编程方式

Question

我正在使用 UIPanGestureRecognizer 方法翻译视图：

 @objc fileprivate func handlePan(_ gestureRecognizer : UIPanGestureRecognizer){
    if gestureRecognizer.state == .began || gestureRecognizer.state == .changed {
        makeDisappearButtons()
        deletebox.isHidden = false
        let translation = gestureRecognizer.translation(in: self.view)
        // note: 'view' is optional and need to be unwrapped
        gestureRecognizer.view!.center = CGPoint(x: gestureRecognizer.view!.center.x + translation.x, y: gestureRecognizer.view!.center.y + translation.y)
        gestureRecognizer.setTranslation(CGPoint.zero, in: self.view)
        if gestureRecognizer.view!.frame.intersects(deletebox.frame) {
            UIView.animate(withDuration: 0.3, delay: 0, options: .curveEaseInOut, animations: {
                gestureRecognizer.view!.transform = .init(scaleX: 0.6, y: 0.6)
                self.deletebox.transform = .init(scaleX: 1.2, y: 1.2)
            }, completion: nil)
        } else {
            gestureRecognizer.view!.setNeedsDisplay()
            gestureRecognizer.setTranslation(.zero, in: self.view)
            UIView.animate(withDuration: 0.3, delay: 0, options: .curveEaseInOut, animations: {
                self.deletebox.transform = .identity
                gestureRecognizer.view!.transform = .identity
            }, completion: nil)
        }
    }
    
    if gestureRecognizer.state == .ended {
        makeButtonsReAppear()
        if gestureRecognizer.view!.frame.intersects(deletebox.frame) {
            gestureRecognizer.view!.isHidden = true
            gestureRecognizer.view?.removeFromSuperview()
        } else {
            gestureRecognizer.view!.setNeedsDisplay()
            gestureRecognizer.setTranslation(.zero, in: self.view)
            gestureRecognizer.view!.transform = .identity
        }
        print(gestureRecognizer.translation(in: self.view))
        deletebox.isHidden = true
    }
}

我想知道 GestureRecognizer.state == .ended 中视图的翻译，但是当我尝试将其打印出来时，它是 x:0, y:0。

Answer 1

每次手势处理程序调用 changed 时，您都将翻译设置回 .zero。

gestureRecognizer.setTranslation(.zero, in: self.view)

但是，当手指抬起时，状态变为ended，到那时翻译不再改变。 documentation 说：

当用户的手指离开屏幕时，手势识别器进入 UIGestureRecognizer.State.ended 状态。

所以在最后一次changed 调用和ended 上的翻译是相同 - 因为你已经设置了gestureRecognizer.view 的框架在changed 内，你不需要在ended 内做任何事情。

Answer 2

你从哪里调用了这个方法，可以放在viewDidAppear中试试。否则调用 setNeedsDisplay 和 LayoutIfNeeded 方法。