仅绘制uilabel周围的顶部，右侧和底部边框 [英] draw only top, right, and bottom border around a uilabel

问题描述

我尝试为uilabel添加边框，但我只想要顶部，右侧和底部边框。

i try to add border for a uilabel, but i only want to have top, right, and bottom border.

喜欢这个

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            I am a label  |
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I尝试使用这些代码，但它默认添加所有4个边

I try to use these codes, but it adds all 4 sides by default

    myLabel.layer.borderWidth = 1;
    myLabel.layer.borderColor = [UIColor blackColor];

无论如何，我只能添加3个边，甚至1个或2个边？

Is that anyway i can only add 3 sides, or even 1 or 2 sides?

谢谢！

推荐答案

您可以使用面具。这是我用来测试理论的代码，效果很好：

You can use a mask. This is the code I used to test the theory, and it works well:

// Define the border width in a variable, we'll be using it elsewhere
CGFloat borderWidth = 1.0;

// This creates a testing view to test the theory, in your case this will be your UILabel
UIView* view = [[UIView alloc] initWithFrame:CGRectMake(20, 60, 250, 100)];
view.layer.borderColor = [UIColor blackColor].CGColor;
view.layer.borderWidth = borderWidth;
[self.view addSubview:view];

// Create the mask to cover the area of the view you want to **show**
// Here, we create a mask that covers most of the view, except the left edge
// The mask needs to be coloured in black, as black acts as transparent, whereas white is opaque in mask parlance
UIView* mask = [[UIView alloc] initWithFrame:CGRectMake(borderWidth, 0, view.frame.size.width - borderWidth, view.frame.size.height)];
mask.backgroundColor = [UIColor blackColor];
view.layer.mask = mask.layer;

您可以调整蒙版的大小和位置（给定borderWidth）以显示/隐藏边框你感兴趣的边缘。上面的例子隐藏了左边缘。

You can adjust the size and position of the mask (given the borderWidth) to show/hide the border edges you're interested in. The example above hides the left edge.

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