如何从其父视图中删除带有圆角的UIView？

问题描述

我正在为3.2和更高版本创建iPad应用程序。我的应用程序有一个重叠视图，具有半透明度，使下面的一切更暗。在这个视图的中间，我在这个半透明的一个洞，让一部分的背景过滤器通过未受伤害的代码：

I'm creating an iPad app for 3.2 and later. My app has an overlay view which has a semi-transparency that makes everything below it darker. In the middle of this view I am chopping a hole in this semi-transparency to let part of the background filter through unscathed, with this code:

- (void)drawRect:(CGRect)rect {
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGRect intersection = CGRectIntersection(hole.frame, rect);
    CGContextClearRect(context, intersection);
}

此外，'hole'视图有圆角， p>

Additionally, the 'hole' view has rounded corners, applied via:

self.layer.cornerRadius = 4.25;

这是一个很好的工作，除了一个小问题 - 这些圆角不考虑，被砍掉的有方角，而不是圆角。我需要解决这个问题，但我不知道如何。任何想法，例子，想法？

This works great except for one small problem - these rounded corners are not taken into account, so the hole that gets chopped out has square corners instead of rounded. I need to fix this, but I have no idea how. Any ideas, examples, thoughts?

推荐答案

这里是我最后得到它的工作。这产生一个与'hole'UIView具有相同框架的孔，从自己（UIView）剪切出来。这可以让你看到后面的洞不受阻碍。

Here's how I ended up getting it to work. This produces a hole with the same frame as the 'hole' UIView, cutting it out from self (UIView). This lets you see whatever is behind the 'hole' unhindered.

- (void)drawRect:(CGRect)rect {
    CGFloat radius = self.hole.layer.cornerRadius;
    CGRect c = self.hole.frame;
    CGContextRef context = UIGraphicsGetCurrentContext();

        // this simply draws a path the same shape as the 'hole' view
    CGContextMoveToPoint(context, c.origin.x, c.origin.y + radius);
    CGContextAddLineToPoint(context, c.origin.x, c.origin.y + c.size.height - radius);
    CGContextAddArc(context, c.origin.x + radius, c.origin.y + c.size.height - radius, radius, M_PI_4, M_PI_2, 1);
    CGContextAddLineToPoint(context, c.origin.x + c.size.width - radius, c.origin.y + c.size.height);
    CGContextAddArc(context, c.origin.x + c.size.width - radius, c.origin.y + c.size.height - radius, radius, M_PI_2, 0.0f, 1);
    CGContextAddLineToPoint(context, c.origin.x + c.size.width, c.origin.y + radius);
    CGContextAddArc(context, c.origin.x + c.size.width - radius, c.origin.y + radius, radius, 0.0f, -M_PI_2, 1);
    CGContextAddLineToPoint(context, c.origin.x + radius, c.origin.y);
    CGContextAddArc(context, c.origin.x + radius, c.origin.y + radius, radius, -M_PI_2, M_PI, 1);

        // finish
    CGContextClosePath(context);
    CGContextClip(context); // this is the secret sauce
    CGContextClearRect(context, c);
}

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