仅在 uilabel 周围绘制顶部、右侧和底部边框

Question

我尝试为 uilabel 添加边框，但我只想拥有top, right, and bottom 边框。

喜欢这个

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            I am a label  |
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我尝试使用这些代码，但默认情况下它会添加所有 4 个面

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

那是不是我只能添加 3 面，甚至 1 或 2 面？

谢谢！

Answer 1

您可以使用面具。这是我用来测试理论的代码，效果很好：

// 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/隐藏您感兴趣的边框边缘。上面的示例隐藏了左边缘。

Answer 2

您必须调整尺寸，但这是要点。 （可能有错别字）

UIView *view = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 320, 35)];
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(10, 15, 320, 20)];

CALayer *bottomBorder = [CALayer layer];
bottomBorder.frame = CGRectMake(0, 40, 320, .5);

CALayer *rightBorder = [CALayer layer];
rightBorder.frame = CGRectMake(320, 0, 40, .5);

CALayer *topBorder = [CALayer layer];
topBorder.frame = CGRectMake(0, 0, 320, .5);

[view.layer addSublayer:bottomBorder];
[view.layer addSublayer:topBorder];
[view.layer addSublayer:rightBorder];
[view.layer addSublayer:label];

Answer 3

您可以通过创建使用 UIBezierPath 的 CALayer 来用一条线绘制您的三个边。在所有示例中，将 QuartzCore 框架作为项目的一部分。

以您的原始代码为起点：

// at the top of the file with this code, include:
#import <QuartzCore/QuartzCore.h>

CGRect rect = myLabel.frame;

UIBezierPath * linePath = [UIBezierPath bezierPath];

// start at top left corner
[linePath moveToPoint:CGPointMake(0,0);
// draw top line across
[linePath addLineToPoint:CGPointMake(rect.size.width, 0);
// draw right vertical side
[linePath addLineToPoint:CGPointMake(rect.size.width, rect.size.height);
// draw left vertical side
[linePath addLineToPoint:CGPointMake(0, rect.size.height);

// draw from bottom right corner back to bottom left corner
[linePath addLineToPoint:CGPointMake(0, rect.size.height);

// create a layer that uses your defined path
CAShapeLayer * lineLayer = [CAShapeLayer layer];
lineLayer.lineWidth = 1.0;
lineLayer.strokeColor = [UIColor blackColor].CGColor;

lineLayer.fillColor = nil;
lineLayer.path = linePath.CGPath;

[myLabel.layer addSublayer:lineLayer];

Answer 4

我正在使用 Swift 3。

// myLabel is a UILabel
let frame = myLabel.frame //Frame of label

// Bottom Layer
let bottomLayer = CALayer()
bottomLayer.frame = CGRect(x: 0, y: frame.height - 1, width: frame.width, height: 1)
bottomLayer.backgroundColor = UIColor.black.cgColor
myLabel.layer.addSublayer(bottomLayer)

// Top Layer
let topLayer = CALayer()
topLayer.frame = CGRect(x: 0, y: 0, width: frame.width, height: 1)
topLayer.backgroundColor = UIColor.black.cgColor
myLabel.layer.addSublayer(topLayer)

同样：

// Right Layer
let rightLayer = CALayer()
rightLayer.frame = CGRect(x: frame.width - 1, y: 0, width: 1, height: frame.height)
rightLayer.backgroundColor = UIColor.black.cgColor
myLabel.layer.addSublayer(rightLayer)

其中 1 是边框的宽度。

Answer 5

你们来了！希望这会有所帮助，将其添加到 UItextfield 覆盖类中

UIView *view = [[UIView alloc] init];
view.translatesAutoresizingMaskIntoConstraints = NO;
view.layer.borderWidth = 1;
view.backgroundColor = [UIColor blackColor];
[self addSubview:view];

[self addConstraint:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeBottom relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeBottom multiplier:1.0 constant:0.0]];
[self addConstraint:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeWidth relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeWidth multiplier:1.0 constant:0.0]];
[self addConstraint:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeHeight relatedBy:NSLayoutRelationEqual toItem:nil attribute:NSLayoutAttributeHeight multiplier:1.0 constant:1.0]];
[self addConstraint:[NSLayoutConstraint constraintWithItem:view attribute:NSLayoutAttributeCenterX relatedBy:NSLayoutRelationEqual toItem:self attribute:NSLayoutAttributeCenterX multiplier:1.0 constant:1.0]];

Answer 6

感谢@jaiswal，我使用了你的代码并创建了一个函数，因为我有超过 10 个 UILabel。我把它放在这里供参考。

 func buttomBoarder(label: UILabel) -> UILabel {
    let frame = label.frame

    let bottomLayer = CALayer()
    bottomLayer.frame = CGRect(x: 0, y: frame.height - 1, width: frame.width, height: 1)
    bottomLayer.backgroundColor = UIColor.black.cgColor
    label.layer.addSublayer(bottomLayer)

    return label

}

调用使用

labelName = buttomBoarder(label: labelName)

Answer 7

你可以继承 UILabel 并覆盖 drawRect: 来做到这一点。

或者您可以只制作 3 个黑色背景的 UIView 作为此标签的子视图。如果您在它们上正确设置 autoresizingMask，它们将根据标签大小的变化进行调整。 上边框应该有灵活的宽度和灵活的下边距，下边框应该有灵活的宽度和灵活的上边距，右边框应该有灵活的高度和灵活的左边距。

Answer 8

您可以通过多种方式做到这一点： 第一个是最简单的，只需找到一个看起来像您的边框笔划的图像。然后在你的 UILabel 后面添加一个 UIImageView。 第二种方法是覆盖 UILabel drawRect: 然后根据您的需要绘制描边。