用另一个CALayer屏蔽CALayer

Question

我正试图用CALayers制作甜甜圈.一个CALayer将是一个大圆圈,另一个将是一个位于其中心的较小圆圈,掩盖它.

大圆圈显示正常,但每当我打电话时circle.mask = circleMask;,视图显示为空.

这是我的代码:

AriDonut.h

#import <UIKit/UIKit.h>

@interface AriDonut : UIView
-(id)initWithRadius:(float)radius;
@end

AriDonut.m

#import "AriDonut.h"
#import <QuartzCore/QuartzCore.h>

@implementation AriDonut

-(id)initWithRadius:(float)radius{
    self = [super initWithFrame:CGRectMake(0, 0, radius, radius)];
    if(self){

        //LARGE CIRCLE
        CALayer *circle = [CALayer layer];
        circle.bounds = CGRectMake(0, 0, radius, radius);
        circle.backgroundColor = [UIColor redColor].CGColor;
        circle.cornerRadius = radius/2;
        circle.position = CGPointMake(radius/2, radius/2);

        //SMALL CIRLCE
        CALayer *circleMask = [CALayer layer];
        circleMask.bounds = CGRectMake(0, 0, 10, 10);
        circleMask.cornerRadius = radius/2;
        circleMask.position = circle.position;

        //circle.mask = circleMask;

        [self.layer addSublayer:circle];

    }

    return self;
}

我试过像这样设置大圆圈的超级层nil:

CALayer *theSuper = circle.superlayer;
theSuper = nil;

但它并没有什么不同.

我也尝试将Circle的masksToBounds属性设置为YES和NO,但它没有任何区别.

有什么想法吗？

Answer 1

实际上,由于@David表示当前(iOS 5.1)CALayer蒙版无法反转,如果您想使用它们将透明孔制作为简单的圆形CALayer,则会出现问题.

你可以做些什么来制作一个圆形的CALayer是backgroundColor透明的,但给它borderColor一个宽的borderWidth.这是dunkin'代码:

    CALayer *theDonut = [CALayer layer];
    theDonut.bounds = CGRectMake(0,0, radius, radius);
    theDonut.cornerRadius = radius/2;
    theDonut.backgroundColor = [UIColor clearColor].CGColor;

    theDonut.borderWidth = radius/5;
    theDonut.borderColor = [UIColor orangeColor].CGColor;

    [self.layer addSublayer:theDonut];

Answer 2

使用UIBezierPath和CAShapeLayer作为屏蔽层非常容易.编写的代码示例就像它在UIView子类中一样.

Objective-C的:

CGRect outerRect = self.bounds;
CGFloat inset = 0.2 * outerRect.size.width; // adjust as necessary for more or less meaty donuts
CGFloat innerDiameter = outerRect.size.width - 2.0 * inset;
CGRect innerRect = CGRectMake(inset, inset, innerDiameter, innerDiameter);
UIBezierPath *outerCircle = [UIBezierPath bezierPathWithRoundedRect:outerRect cornerRadius:outerRect.size.width * 0.5];
UIBezierPath *innerCircle = [UIBezierPath bezierPathWithRoundedRect:innerRect cornerRadius:innerRect.size.width * 0.5];
[outerCircle appendPath:innerCircle];
CAShapeLayer *maskLayer = [CAShapeLayer new];
maskLayer.fillRule = kCAFillRuleEvenOdd; // Going from the outside of the layer, each time a path is crossed, add one. Each time the count is odd, we are "inside" the path.
maskLayer.path = outerCircle.CGPath;
self.layer.mask = maskLayer;

迅速:

let outerRect = self.bounds
let inset: CGFloat = 0.2 * outerRect.width // adjust as necessary for more or less meaty donuts
let innerDiameter = outerRect.width - 2.0 * inset
let innerRect = CGRect(x: inset, y: inset, width: innerDiameter, height: innerDiameter)
let outerCircle = UIBezierPath(roundedRect: outerRect, cornerRadius: outerRect.width * 0.5)
let innerCircle = UIBezierPath(roundedRect: innerRect, cornerRadius: innerRect.width * 0.5)
outerCircle.appendPath(innerCircle)
let mask = CAShapeLayer()
mask.fillRule = kCAFillRuleEvenOdd
mask.path = outerCircle.CGPath
self.layer.mask = mask

Answer 3

它是用作遮罩的遮罩层内容的alpha值.(如果要将蒙版添加为子图层而不是将其用作蒙版.当用作蒙版时,子图层覆盖的所有内容都将可见.当用作蒙版时,子图层未覆盖的所有内容都将被隐藏.)

由于您的小圆圈是完全透明的,所以一切都被掩盖了(隐藏).如果你将backgroundColor它设置为任何完全不透明的颜色(只有alpha值用于蒙版),那么它将让这些像素通过.

请注意,这与您想要的相反.这将使您只看到"甜甜圈的洞"可见.没有内置的方法来做反向掩码相反,你必须以其他方式绘制掩码的内容,如使用CAShapeLayer或使用drawInContext:.