为CGAffineTransformMakeRotation Swift设置旋转点

我正在使用下面的代码来旋转UIImageViews到不同的angular度。

self.imageOne.transform = CGAffineTransformMakeRotation(CGFloat(-rotation)) self.imageTwo.transform = CGAffineTransformMakeRotation(CGFloat(-rotation-0.1)) self.imageThree.transform = CGAffineTransformMakeRotation(CGFloat(-change+0.1)) 

有什么办法可以使图像从顶部而不是从中间旋转？ 我想避免让精灵参与，因为我从来没有使用过它们，也不知道如何使精灵在单一视图应用程序中工作。 谢谢你的时间。

Answer 1

你正在寻找的是你的视图层的anchorPoint属性。 这个属性基本上代表了视图被移动时使用的句柄 。

它默认为视图的中心，所以你总是看到你的视图从中间旋转。

您可以使用我在这里find的这个伟大的方法来将您的视图的anchorPoint更改为顶部（使用CGPointMake（0，0.5f））

 // Swift version // Place this before you set the transform property setAnchorPoint(CGPointMake(0, 0.5), view: imageOne) setAnchorPoint(CGPointMake(0, 0.5), view: imageTwo) setAnchorPoint(CGPointMake(0, 0.5), view: imageThree) func setAnchorPoint(anchorPoint: CGPoint, view: UIView) { var newPoint = CGPointMake(view.bounds.size.width * anchorPoint.x, view.bounds.size.height * anchorPoint.y) var oldPoint = CGPointMake(view.bounds.size.width * view.layer.anchorPoint.x, view.bounds.size.height * view.layer.anchorPoint.y) newPoint = CGPointApplyAffineTransform(newPoint, view.transform) oldPoint = CGPointApplyAffineTransform(oldPoint, view.transform) var position : CGPoint = view.layer.position position.x -= oldPoint.x position.x += newPoint.x; position.y -= oldPoint.y; position.y += newPoint.y; view.layer.position = position; view.layer.anchorPoint = anchorPoint; } 

这是相同代码的目标c版本

 // Obj-c version // Place this before you set the transform property [self setAnchorPoint:CGPointMake(0, 0.5f) forView:imageOne]; [self setAnchorPoint:CGPointMake(0, 0.5f) forView:imageTwo]; [self setAnchorPoint:CGPointMake(0, 0.5f) forView:imageThree]; -(void)setAnchorPoint:(CGPoint)anchorPoint forView:(UIView *)view { CGPoint newPoint = CGPointMake(view.bounds.size.width * anchorPoint.x, view.bounds.size.height * anchorPoint.y); CGPoint oldPoint = CGPointMake(view.bounds.size.width * view.layer.anchorPoint.x, view.bounds.size.height * view.layer.anchorPoint.y); newPoint = CGPointApplyAffineTransform(newPoint, view.transform); oldPoint = CGPointApplyAffineTransform(oldPoint, view.transform); CGPoint position = view.layer.position; position.x -= oldPoint.x; position.x += newPoint.x; position.y -= oldPoint.y; position.y += newPoint.y; view.layer.position = position; view.layer.anchorPoint = anchorPoint; } 

我鼓励你一旦看到了anchorPoint属性代表什么，就试着去了解自己的代码是做什么的。 （该方法是由用户： Anand K ）

Answer 2

这是一个基于mttcrp的答案的Swift 3扩展。 我花了一段时间才发现CGPoint不是一个坐标，而是一个比例。 例如，如果您围绕CGPoint(x: 0.5, y: 1)旋转视图，它将围绕视图的底部中心旋转。 希望这可以帮助！

 extension UIView{ func setAnchorPoint(anchorPoint: CGPoint) { var newPoint = CGPoint(x: self.bounds.size.width * anchorPoint.x, y: self.bounds.size.height * anchorPoint.y) var oldPoint = CGPoint(x: self.bounds.size.width * self.layer.anchorPoint.x, y: self.bounds.size.height * self.layer.anchorPoint.y) newPoint = newPoint.applying(self.transform) oldPoint = oldPoint.applying(self.transform) var position : CGPoint = self.layer.position position.x -= oldPoint.x position.x += newPoint.x; position.y -= oldPoint.y; position.y += newPoint.y; self.layer.position = position; self.layer.anchorPoint = anchorPoint; } } 

你可以像这样使用它：

 let view = UIView() //This could be anything that inherits from UIView view.setAnchorPoint(anchorPoint: CGPoint(x: 0.5, y: 1))