更改我的CALayer的anchorPoint会移动视图

Question

我想改变anchorPoint,但保持视图在同一个地方.我试过NSLog-ing分词self.layer.position和self.center他们都保持不变,无论更改anchorPoint的.然而我的观点却在变化

关于如何做到这一点的任何提示？

self.layer.anchorPoint = CGPointMake(0.5, 0.5);
NSLog(@"center point: %f %f", self.layer.position.x, self.layer.position.y);
self.layer.anchorPoint = CGPointMake(1, 1);
NSLog(@"center point: %f %f", self.layer.position.x, self.layer.position.y);

输出是:

2009-12-27 20:43:24.161 Type[11289:207] center point: 272.500000 242.500000
2009-12-27 20:43:24.162 Type[11289:207] center point: 272.500000 242.500000

Answer 1

我有同样的问题.Brad Larson的解决方案即使在旋转视图时也能很好地工作.这是他的解决方案翻译成代码.

-(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;
}

而快速的等价物:

func setAnchorPoint(anchorPoint: CGPoint, forView 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 = 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
}

SWIFT 4.x

func setAnchorPoint(anchorPoint: CGPoint, forView view: UIView) {
    var newPoint = CGPoint(x: view.bounds.size.width * anchorPoint.x,
                           y: view.bounds.size.height * anchorPoint.y)


    var oldPoint = CGPoint(x: view.bounds.size.width * view.layer.anchorPoint.x,
                           y: view.bounds.size.height * view.layer.anchorPoint.y)

    newPoint = newPoint.applying(view.transform)
    oldPoint = oldPoint.applying(view.transform)

    var 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
}

Answer 2

Core Animation Programming Guide 的Layer Geometry and Transforms部分解释了CALayer的position和anchorPoint属性之间的关系.基本上,层的位置是根据图层的anchorPoint的位置指定的.默认情况下,图层的anchorPoint为(0.5,0.5),位于图层的中心.设置图层的位置时,您将在其超层的坐标系中设置图层中心的位置.

因为位置是相对于图层的anchorPoint,所以在保持相同位置的同时更改该anchorPoint会移动图层.为了防止这种移动,您需要调整图层的位置以考虑新的anchorPoint.我这样做的一种方法是抓取图层的边界,将边界的宽度和高度乘以旧的和新的anchorPoint的标准化值,取两个anchorPoints的差值,并将该差值应用于图层的位置.

您甚至可以通过使用CGPointApplyAffineTransform()UIView的CGAffineTransform以这种方式考虑轮换.

Answer 3

解决这个问题的关键是使用frame属性,这是奇怪的唯一改变.

斯威夫特2

let oldFrame = self.frame
self.layer.anchorPoint = CGPointMake(1, 1)
self.frame = oldFrame

斯威夫特3

let oldFrame = self.frame
self.layer.anchorPoint = CGPoint(x: 1, y: 1)
self.frame = oldFrame

然后我做我的调整大小,它从anchorPoint扩展.然后我必须恢复旧的anchorPoint;

斯威夫特2

let oldFrame = self.frame
self.layer.anchorPoint = CGPointMake(0.5,0.5)
self.frame = oldFrame

斯威夫特3

let oldFrame = self.frame
self.layer.anchorPoint = CGPoint(x: 0.5, y: 0.5)
self.frame = oldFrame

编辑:如果视图被旋转,这会剥落,因为如果已应用CGAffineTransform,则帧属性未定义.

Answer 4

当我开始将它与我对UIView中的frame.origin的理解进行比较时,对我来说理解position并且anchorPoint是最简单的.带有frame.origin =(20,30)的UIView意味着UIView距左侧20点,距其父视图顶部30点.这个距离是从UIView的哪个点算出的？它是从UIView的左上角计算出来的.

在层中anchorPoint标记计算该距离的点(以标准化形式,即0到1),例如,layer.position =(20,30)表示该层anchorPoint距离其父层的左侧20个点和顶部30个点.默认情况下,图层anchorPoint为(0.5,0.5),因此距离计算点位于图层的中心.下图将有助于澄清我的观点:

anchorPoint 也恰好是在将变换应用于图层时将发生旋转的点.

Answer 5

有这么简单的解决方案.这是基于Kenny的回答.但是,不是应用旧框架,而是使用它的原点和新框架来计算过渡,然后将该过渡应用到中心.它也适用于旋转视图!这是代码,比其他解决方案简单得多:

func setAnchorPoint(anchorPoint: CGPoint, view: UIView) {
   let oldOrigin = view.frame.origin
   view.layer.anchorPoint = anchorPoint
   let newOrigin = view.frame.origin

   let translation = CGPoint(x: newOrigin.x - oldOrigin.x, y: newOrigin.y - oldOrigin.y)

   view.center = CGPoint(x: view.center.x - translation.x, y: view.center.y - translation.y)
}

和Swift版本:

func setAnchorPoint(anchorPoint: CGPoint, view: UIView) {
   let oldOrigin = view.frame.origin
   view.layer.anchorPoint = anchorPoint
   let newOrigin = view.frame.origin

   let translation = CGPoint(x: newOrigin.x - oldOrigin.x, y: newOrigin.y - oldOrigin.y)

   view.center = CGPoint(x: view.center.x - translation.x, y: view.center.y - translation.y)
}

Answer 6

对于那些需要它的人来说,这是Magnus在Swift中的解决方案:

func setAnchorPoint(anchorPoint: CGPoint, view: UIView) {
    var newPoint: CGPoint = CGPointMake(view.bounds.size.width * anchorPoint.x, view.bounds.size.height * anchorPoint.y)
    var oldPoint: CGPoint = 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.setTranslatesAutoresizingMaskIntoConstraints(true)     // Added to deal with auto layout constraints
    view.layer.anchorPoint = anchorPoint
    view.layer.position = position
}

Answer 7

这是针对OS X上的NSView调整的user945711的答案.除了NSView没有.center属性之外,NSView的框架不会改变(可能是因为NSView默认情况下不带CALayer)但是当更改anchorPoint时CALayer框架原点会发生变化.

func setAnchorPoint(anchorPoint: NSPoint, view: NSView) {
    guard let layer = view.layer else { return }

    let oldOrigin = layer.frame.origin
    layer.anchorPoint = anchorPoint
    let newOrigin = layer.frame.origin

    let transition = NSMakePoint(newOrigin.x - oldOrigin.x, newOrigin.y - oldOrigin.y)
    layer.frame.origin = NSMakePoint(layer.frame.origin.x - transition.x, layer.frame.origin.y - transition.y)
}