为 CGAffineTransformMakeRotation Swift 设置旋转点 [英] Setting a rotation point for CGAffineTransformMakeRotation Swift

问题描述

我正在使用下面的代码将 UIImageViews 旋转到不同的角度.

I am using the code below to rotate UIImageViews to different angles.

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中间旋转?我想避免涉及精灵，因为我从未使用过它们，也不知道如何使精灵在单视图应用程序中工作.谢谢你的时间.

Is there any way to make it so the images pivot from the top instead of the middle? I would like to avoid getting sprites involved because I have never used them, and don't know how to make sprites work in a single view application. Thanks for your time.

推荐答案

您正在寻找的是 anchorPoint 视图层的属性.这个属性基本上代表了在移动视图时使用的句柄.

What you are looking for is the anchorPoint property of your views' layers. This property basically represents the handle that is be used while the view is being moved around.

它默认为您视图的中心，这就是为什么您总是看到您的视图从中间旋转.

It defaults to the center of your view so and that why you are always seeing your view rotating form the middle.

您可以使用我在 SO 上找到的这个很棒的方法将视图的锚点更改为顶部(使用 CGPointMake(0, 0.5f))

You can use this great method i've found here on SO to change the anchorPoint of you views to the top (use 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;
}

这是同一代码的客观c版本

This is the objective c version of the same code

// 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;
}

一旦您了解了 anchorPoint 属性所代表的含义，我鼓励您尝试了解自己这段代码的作用.(方法是用户:Anand K)

I'd encourage you to try to understand yourself what this code is doing once you have seen what the anchorPoint property represents. (the method is by user: Anand K)

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