Question

我创建了5个UIViews，每个UIView都有UIPanGestureRecognizers，然后我将其添加到另一个UIView中。这一切都有效，我可以拖动每个，但我不希望它们被拖到他们的父UIView边界之外。我已经读过我可以使用gestureRecognizerShouldBegin函数实现UIGestureRecognizerDelegate来实现这一目标，但我找不到足够的文档来确切地知道如何实现我所需要的。像往常一样，Apple关于此的文档非常模糊。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
        }
    }

上面的代码在平移/拖动方面我需要它做的很好。我还扩展了我的ViewController以符合UIGestureRecognizerDelegate

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

    }
}

但我不确定从这里开始如何限制父视图边界内的可拖动视图。有人可以帮忙吗？

Answer 1

你必须做一些计算，我希望这段代码可以帮助你。

@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，委托不适合这件事。我相信你想要保持手势，只是将你的观点的位置限制在他们的父母内部。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)
}

所以基本上我们正在计算新的左上角和右下角。如果这些在他们的超视图范围内，那么视图可能会移动到那一点。

这是相当不错的，但事情是，一旦发生这种情况，您的视图可能不会完全位于边界。例如，如果用户将其向左拖动非常快，那么在某些时候topLeft可能是(15, 0)，而在下一个事件中(-10, 0)这意味着它将忽略第二个并保持在{{1 }}

所以你需要实现限制移动并限制它...

(15, 0)

所以这应该让你的观点坚持在超级视图中......

设置平移手势的边界

2 个答案: