Question

只希望图像向上平移。

我尝试编辑x和y坐标。尝试根据翻译生成新的y变量，但不会更改。

@objc func handleVerticalPan(_ recognizer: UIPanGestureRecognizer)     {
    let translation: CGPoint = recognizer.translation(in: self.view)
    var newY = view.center.y + translation.y
        startingPoint = recognizer.view!.center
        recognizer.view?.superview?.bringSubviewToFront(recognizer.view!)
        if newY > translation.y
        {
            recognizer.view?.center = CGPoint(x: recognizer.view!.center.x, y: recognizer.view!.center.y + translation.y)
            newY = view.center.y + translation.y
            recognizer.setTranslation(CGPoint(x: 0, y: 0), in: self.view)
            //startingPoint = recognizer.view!.center
        }

它会上下移动，但我只希望它向上移动。

Answer 1

您正在比较错误的变量，并且Y值沿向下方向增加。您需要检查的是transition.y是否为负（即向上移动）：

替换此：

if newY > translation.y

与此：

if transition.y < 0

实际上，根本不需要newY：

@objc func handleVerticalPan(_ recognizer: UIPanGestureRecognizer) {
    let translation = recognizer.translation(in: self.view)
    guard let view = recognizer.view else { return }

    view.superview?.bringSubviewToFront(view)

    // If the movement is upward (-Y direction):
    if translation.y < 0
    {
        view.center = CGPoint(x: view.center.x, y: view.center.y + translation.y)
        recognizer.setTranslation(.zero, in: self.view)
    }
}

注释：

其他更改：

使用guard安全地解包recognizer.view一次，而不是在整个代码中重复解包。
将CGPoint(x: 0, y: 0)替换为.zero，Swift认为CGPoint.zero是CGPoint。

将平移手势限制为一个方向

1 个答案: