在平移手势上设置边界

Question

我创建了5个UIView，每个UIView都有UIPanGestureRecognizers，然后将它们添加到另一个UIView中。 所有这些工作正常，我可以将它们拖到各处，但我不希望它们被拖到其父UIView的边界之外。 我已经读过我可以使用gestureRecognizerShouldBegin函数实现UIGestureRecognizerDelegate来实现此目的，但是我找不到足够的文档来确切地了解如何实现所需的功能。 和往常一样，苹果公司对此的文件含糊不清。 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
        }
    }

上面的代码在平移/拖动方面需要我做的很好。 我还扩展了ViewController以使其符合UIGestureRecognizerDelegate

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

    }
}

但是我不确定如何将可拖动视图限制在其父视图的范围之内，从何而来。 有人可以帮忙吗？

Answer 1

您必须进行一些计算，希望这段代码对您有所帮助。

@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，委托不适合这个事情。 我相信您想保持手势，只是将视图的位置限制在其父视图之内。 为此，您需要限制平移手势更改事件。

最简单的方法是检查两个相对的点是否在父矩形内：

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)
}

因此，基本上，我们正在计算新的左上和右下点。 并且如果这些在其超级视图范围之内，则视图可能会移至该点。

这是相当不错的，但事实是，一旦发生这种情况，您的视线可能就不会完全在边界处。 例如，如果用户将它真正快速地向左拖动，则在某个点topLeft可能是(15, 0) topLeft (15, 0) ，在下一个事件中(-10, 0) topLeft (-10, 0)意味着这将忽略第二个，并保持在(15, 0) topLeft (15, 0) 。

因此，您需要将limi实现为运动并将其限制为运动...

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内...