[英]Limiting pan gesture to one direction
Would like to have the image only pan upwards. 希望图像仅向上平移。
I have tried to edit the x and y coordinates. 我试图编辑x和y坐标。 Tried to to make a new y variable based on the translation but does not change. 尝试根据转换生成新的y变量,但不更改。
@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
}
It will pan up and down but I only want it to go up. 它会上下移动,但我只希望它向上移动。
You are comparing the wrong variables, and Y
values increase in the downward direction. 您正在比较错误的变量,并且Y
值沿向下方向增加。 All you need to check is that transition.y
is negative (ie. moving upward): 您需要检查的是transition.y
为负(即向上移动):
Replace this: 替换为:
if newY > translation.y
with this: 有了这个:
if transition.y < 0
In fact, newY
isn't really needed at all: 实际上, newY
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)
}
}
Notes: 笔记:
Other changes made: 进行的其他更改:
guard
to safely unwrap recognizer.view
once instead of repeatedly unwrapping it throughout the code. 使用过guard
可以安全地一次解开recognizer.view
.view,而不是在整个代码中反复解开它。 CGPoint(x: 0, y: 0)
with .zero
which Swift infers to be CGPoint.zero
since it is expecting a CGPoint
. 用.zero
替换了CGPoint(x: 0, y: 0)
,Swift推断它为CGPoint.zero
因为它期望一个CGPoint
。
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