ios - 从.began到.changed分配UIPanGestureRecognizer中的CGPoint

在我的视图内部，我有一个cardContainerView并附加了UIPanGestureRecognizer。根据用户是抓住卡片的上半部还是下半部，我想为卡片添加不同的旋转角度，现在可以正常使用了。

我的问题是我实现它的方式，用户可以抓住卡的顶部(导致正旋转)并将卡滑动到location.y阈值以下，然后导致卡使用负值旋转角度。这会引起卡的剧烈跳动。

我试图抓住.began部分中的location.y并将其分配给.changed，但显然我不能这样做。结果为零。有人知道我还能怎么解决吗？

非常感激!

    //When animation begins
    if sender.state == UIGestureRecognizerState.began {
        print("PAN BEGAN")
        cardContainerViewInitialCenter = cardContainerView.center
        addNewTempCard()
        initialPoint = location
        print("InitialPoint PAN BEGAN \(initialPoint)")
        print("InitialPoint.y PAN BEGAN \(initialPoint.y)")
    }

    //While panning
    else if sender.state == UIGestureRecognizerState.changed {
        print("PAN CHANGED")

        //User grabbed card at top half
        if location.y < view.frame.height/2 {
            print("TOP HALF")

            if translation.x >= 0 && translation.x <= 50 {
                cardContainerView.center = CGPoint(x: cardContainerViewInitialCenter.x + translation.x, y: cardContainerViewInitialCenter.y)
                cardContainerView.transform = CGAffineTransform.init(rotationAngle: convertedRotationTopPos)
                tempCardView.alpha = convertedNewCardAlphaPos
                tempCardView.transform = view.transform.scaledBy(x: convertedNewCardScaleXPos, y: convertedNewCardScaleYPos)
            }

            else if translation.x > 50 {
                cardContainerView.center = CGPoint(x: cardContainerViewInitialCenter.x + translation.x, y: cardContainerViewInitialCenter.y)
                cardContainerView.transform = CGAffineTransform.init(rotationAngle: convertedRotationTopPos)
                tempCardView.alpha = convertedNewCardAlphaPos
                tempCardView.transform = view.transform.scaledBy(x: convertedNewCardScaleXPos, y: convertedNewCardScaleYPos)
            }

            else if translation.x < 0 && translation.x >= -50 {
                cardContainerView.center = CGPoint(x: cardContainerViewInitialCenter.x + translation.x, y: cardContainerViewInitialCenter.y)
                cardContainerView.transform = CGAffineTransform.init(rotationAngle: convertedRotationTopNeg)
                tempCardView.alpha = convertedNewCardAlphaNeg
                tempCardView.transform = view.transform.scaledBy(x: convertedNewCardScaleXNeg, y: convertedNewCardScaleYNeg)
            }

            else if translation.x < -50 {
                cardContainerView.center = CGPoint(x: cardContainerViewInitialCenter.x + translation.x, y: cardContainerViewInitialCenter.y)
                cardContainerView.transform = CGAffineTransform.init(rotationAngle: convertedRotationTopNeg)
                tempCardView.alpha = convertedNewCardAlphaNeg
                tempCardView.transform = view.transform.scaledBy(x: convertedNewCardScaleXNeg, y: convertedNewCardScaleYNeg)
            }
        }

        //User grabbed card at bottom half
        else if location.y > view.frame.height/2 {
            print("TOP HALF")

            if translation.x >= 0 && translation.x <= 50 {
                cardContainerView.center = CGPoint(x: cardContainerViewInitialCenter.x + translation.x, y: cardContainerViewInitialCenter.y)
                cardContainerView.transform = CGAffineTransform.init(rotationAngle: convertedRotationBottomPos)
                tempCardView.alpha = convertedNewCardAlphaPos
                tempCardView.transform = view.transform.scaledBy(x: convertedNewCardScaleXPos, y: convertedNewCardScaleYPos)
            }

            else if translation.x > 50 {
                cardContainerView.center = CGPoint(x: cardContainerViewInitialCenter.x + translation.x, y: cardContainerViewInitialCenter.y)
                cardContainerView.transform = CGAffineTransform.init(rotationAngle: convertedRotationBottomPos)
                tempCardView.alpha = convertedNewCardAlphaPos
                tempCardView.transform = view.transform.scaledBy(x: convertedNewCardScaleXPos, y: convertedNewCardScaleYPos)
            }

            else if translation.x < 0 && translation.x >= -50 {
                cardContainerView.center = CGPoint(x: cardContainerViewInitialCenter.x + translation.x, y: cardContainerViewInitialCenter.y)
                cardContainerView.transform = CGAffineTransform.init(rotationAngle: convertedRotationBottomNeg)
                tempCardView.alpha = convertedNewCardAlphaNeg
                tempCardView.transform = view.transform.scaledBy(x: convertedNewCardScaleXNeg, y: convertedNewCardScaleYNeg)
            }

            else if translation.x < -50 {
                cardContainerView.center = CGPoint(x: cardContainerViewInitialCenter.x + translation.x, y: cardContainerViewInitialCenter.y)
                cardContainerView.transform = CGAffineTransform.init(rotationAngle: convertedRotationBottomNeg)
                tempCardView.alpha = convertedNewCardAlphaNeg
                tempCardView.transform = view.transform.scaledBy(x: convertedNewCardScaleXNeg, y: convertedNewCardScaleYNeg)
            }
        }
    }

最佳答案

我认为您应该将intialPoint设置为.began状态。在.changed中不应为零

//When animation begins
if sender.state == .began {
    ...
    initialPoint = sender.location(in: self)
}

我也不认为else确实对您有帮助。它不应该是.began，而不是.changed，而是检查.began和.changed。

关于ios - 从.began到.changed分配UIPanGestureRecognizer中的CGPoint，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/47727021/