需要协助设置遮罩层锚点

Question

CALayer *mask = [CALayer layer];
mask.contents = (id)[[self getImg]CGImage];
mask.frame = CGRectMake(0, 0, self.vview.frame.size.width, 100);
mask.anchorPoint = CGPointMake(0.5, 1.0);
self.vview.layer.mask = mask;

我正在尝试在我的UIView vview 上设置蒙版，vview 的高度为 300，但是当我设置 anchor point 时，蒙版层跳了大约 50 像素，我应该怎么做才能保持其原始位置。

没有任何遮罩的绿色视图

带遮罩但没有锚点的绿色 vview

带有遮罩和锚点的绿色 vview

Answer 1

关于锚点的文档：

anchorPoint
 Property
Defines the anchor point of the layer's bounds rectangle. Animatable.

Declaration
SWIFT
var anchorPoint: CGPoint
OBJECTIVE-C
@property CGPoint anchorPoint
Discussion
You specify the value for this property using the unit coordinate space. The default value of this property is (0.5, 0.5), which represents the center of the layer’s bounds rectangle. All geometric manipulations to the view occur about the specified point. For example, applying a rotation transform to a layer with the default anchor point causes the layer to rotate around its center. Changing the anchor point to a different location would cause the layer to rotate around that new point.

For more information about the relationship between the frame, bounds, anchorPoint and position properties, see Core Animation Programming Guide.

几何操作：https://developer.apple.com/library/ios/documentation/Cocoa/Conceptual/CoreAnimation_guide/CoreAnimationBasics/CoreAnimationBasics.html

基于此，如果您不想移动蒙版，只需将锚点设置为

mask.anchorPoint = CGPointMake(0.5,0.5);

这是默认值。