设置平移手势的边界

Question

我创建了 5 个 UIView，每个都带有 UIPanGestureRecognizers，然后我将其添加到另一个 UIView。所有这些都有效，我可以四处拖动，但我不希望它们被拖到它们的父 UIView 的边界之外。我读过我可以使用 gestureRecognizerShouldBegin 函数实现 UIGestureRecognizerDelegate 来实现这一点，但是我找不到足够的文档来准确说明如何实现我所需要的。像往常一样，Apple 对此的文档非常模糊。我的代码是：

    let foreheadTopViewWidth = foreheadTopView.frame.width
            let foreheadTopViewHeight = foreheadTopView.frame.height
            let touchPointOffset = touchPointSize / 2
            let touchPointYPos = (foreheadTopViewHeight / 2) - touchPointOffset

            let touchPointForehead1 = TouchPoint(touchPointSize: touchPointSize, xPosition: 0, yPosition: touchPointYPos, treatmentArea: .upperForehead)
            let touchPointForehead2 = TouchPoint(touchPointSize: touchPointSize, xPosition: ((foreheadTopViewWidth * 0.50) - touchPointOffset) / 2, yPosition: touchPointYPos, treatmentArea: .upperForehead)
            let touchPointForehead3 = TouchPoint(touchPointSize: touchPointSize, xPosition: (foreheadTopViewWidth * 0.50) - touchPointOffset, yPosition: touchPointYPos, treatmentArea: .upperForehead)
            let touchPointForehead4 = TouchPoint(touchPointSize: touchPointSize, xPosition: (foreheadTopViewWidth * 0.75) - (touchPointOffset / 0.75), yPosition: touchPointYPos, treatmentArea: .upperForehead)
            let touchPointForehead5 = TouchPoint(touchPointSize: touchPointSize, xPosition: foreheadTopViewWidth - touchPointSize, yPosition: touchPointYPos, treatmentArea: .upperForehead)

            foreheadTopView.addSubview(touchPointForehead1)
            foreheadTopView.addSubview(touchPointForehead2)
            foreheadTopView.addSubview(touchPointForehead3)
            foreheadTopView.addSubview(touchPointForehead4)
            foreheadTopView.addSubview(touchPointForehead5)

            let foreheadGesture1 = UIPanGestureRecognizer(target: self, action: #selector(didPan(gesture:)))
            let foreheadGesture2 = UIPanGestureRecognizer(target: self, action: #selector(didPan(gesture:)))
            let foreheadGesture3 = UIPanGestureRecognizer(target: self, action: #selector(didPan(gesture:)))
            let foreheadGesture4 = UIPanGestureRecognizer(target: self, action: #selector(didPan(gesture:)))
            let foreheadGesture5 = UIPanGestureRecognizer(target: self, action: #selector(didPan(gesture:)))
            foreheadGesture1.delegate = self
            foreheadGesture2.delegate = self
            foreheadGesture3.delegate = self
            foreheadGesture4.delegate = self
            foreheadGesture5.delegate = self

            touchPointForehead1.addGestureRecognizer(foreheadGesture1)
            touchPointForehead2.addGestureRecognizer(foreheadGesture2)
            touchPointForehead3.addGestureRecognizer(foreheadGesture3)
            touchPointForehead4.addGestureRecognizer(foreheadGesture4)
            touchPointForehead5.addGestureRecognizer(foreheadGesture5)

            foreheadTopView.layer.addSublayer(touchPointForehead1.lineTo(touchpoint: touchPointForehead2))
            foreheadTopView.layer.addSublayer(touchPointForehead2.lineTo(touchpoint: touchPointForehead3))
            foreheadTopView.layer.addSublayer(touchPointForehead3.lineTo(touchpoint: touchPointForehead4))
            foreheadTopView.layer.addSublayer(touchPointForehead4.lineTo(touchpoint: touchPointForehead5))

@objc func didPan(gesture: UIPanGestureRecognizer) {

        guard let touchpoint = gesture.view as? TouchPoint else {
            return
        }
        if (gesture.state == .began) {
            touchpoint.center = gesture.location(in: foreheadTopView)
        }

        let newCenter: CGPoint = gesture.location(in: foreheadTopView)
        let dX = newCenter.x - touchpoint.center.x
        let dY = newCenter.y - touchpoint.center.y
        touchpoint.center = CGPoint(x: touchpoint.center.x + dX, y: touchpoint.center.y + dY)

        if let outGoingTouchPoint = touchpoint.outGoingTouchPoint, let line = touchpoint.outGoingLine, let path = touchpoint.outGoingLine?.path {
            let newPath = UIBezierPath(cgPath: path)
            newPath.removeAllPoints()
            newPath.move(to: touchpoint.center)
            newPath.addLine(to: outGoingTouchPoint.center)
            line.path = newPath.cgPath
        }

        if let inComingTouchPoint = touchpoint.inComingTouchPoint, let line = touchpoint.inComingLine, let path = touchpoint.inComingLine?.path {
            let newPath = UIBezierPath(cgPath: path)
            newPath.removeAllPoints()
            newPath.move(to: inComingTouchPoint.center)
            newPath.addLine(to: touchpoint.center)
            line.path = newPath.cgPath
        }
    }

根据 panning/dragging 的要求，上面的代码工作正常。我还扩展了我的 ViewController 以符合 UIGestureRecognizerDelegate

extension ViewController: UIGestureRecognizerDelegate {
    func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool {

    }
}

但我不确定如何将可拖动视图限制在其父视图的边界内。有人可以帮忙吗？

Answer 1

你要做一些计算，希望这段代码能帮到你。

@objc func handlepan(_ gesture:UIPanGestureRecognizer)
{
    let translation = gesture.translation(in: self.imagelayer)
    if let view1 = gesture.view {

        if (view1.frame.origin.x + translation.x >= 0) && (view1.frame.origin.y + translation.y >= 0) && (view1.frame.origin.x + translation.x <= view1.frame.width ) && (view1.frame.origin.y + translation.y <= view1.frame.height)
        {
        view1.center = CGPoint(x:view1.center.x + translation.x,
                              y:view1.center.y + translation.y)
        }
    }
    gesture.setTranslation(CGPoint.zero, in: self.imagelayer)
}

Answer 2

不，委托不适合做这件事。我相信你想保持手势并且只是将你的视图的位置限制在他们的 parent 内。为此，您需要限制平移手势更改事件。

最简单的是检查两个相对的点是否在parent rect:

内

let topLeft = CGPoint(x: touchpoint.frame.minX + dX, y: touchpoint.frame.minY + dY)
let bottomRight = CGPoint(x: touchpoint.frame.maxX + dX, y: touchpoint.frame.maxY + dY)
if let containerView = touchpoint.superview, containerView.bounds.contains(topLeft), containerView.bounds.contains(bottomRight) {
    touchpoint.center = CGPoint(x: touchpoint.center.x + dX, y: touchpoint.center.y + dY)
}

所以基本上我们正在计算新的 top-left 和 bottom-right 点。如果它们在它们的超级视图范围内，则视图可能会移动到该点。

这很好，但问题是，一旦发生这种情况，您的视图可能不在边界处。例如，如果用户非常快地将它向左拖动，那么在某个时候 topLeft 可能是 (15, 0) 并且在下一个事件中 (-10, 0) 这意味着它将忽略第二个并保持在 (15, 0).

所以你需要实现移动限制并限制它...

var targetFrame = CGRect(x: touchpoint.frame.origin.x + dX, y: touchpoint.frame.origin.y + dY, width: touchpoint.frame.width, height: touchpoint.frame.height)

if let containerView = touchpoint.superview {
    targetFrame.origin.x = max(0.0, targetFrame.origin.x)
    targetFrame.origin.y = max(0.0, targetFrame.origin.y)
    targetFrame.size.width = min(targetFrame.size.width, containerView.bounds.width-(targetFrame.origin.x+targetFrame.width))
    targetFrame.size.height = min(targetFrame.size.height, containerView.bounds.height-(targetFrame.origin.y+targetFrame.height))
}

touchpoint.frame = targetFrame

所以这应该使您的视图停留在超级视图中...

设置平移手势的边界

Setting boundaries on pan gestures

ios

swift

uipangesturerecognizer