UIButton 中的文本下划线

要使用界面生成器来下划线，必须：

将其更改为归因

突出显示属性检查器中的文本

右键单击，选择字体，然后下划线

https://i.stack.imgur.com/yfYRv.png

其他人制作的视频 https://www.youtube.com/watch?v=5-ZnV3jQd9I

---

从 iOS6 开始，现在可以使用 NSAttributedString 以更灵活的方式执行下划线（以及任何其他属性字符串支持）：

NSMutableAttributedString *commentString = [[NSMutableAttributedString alloc] initWithString:@"The Quick Brown Fox"];

[commentString addAttribute:NSUnderlineStyleAttributeName value:[NSNumber numberWithInteger:NSUnderlineStyleSingle] range:NSMakeRange(0, [commentString length])];

[button setAttributedTitle:commentString forState:UIControlStateNormal];

注意：将此添加为另一个答案 - 因为它与我之前的解决方案完全不同。

编辑：奇怪的是（至少在 iOS8 中）你必须在第一个字符下划线，否则它不起作用！

因此，作为一种解决方法，将第一个字符设置为清晰的颜色下划线！

    // underline Terms and condidtions
    NSMutableAttributedString* tncString = [[NSMutableAttributedString alloc] initWithString:@"View Terms and Conditions"];

    // workaround for bug in UIButton - first char needs to be underlined for some reason!
    [tncString addAttribute:NSUnderlineStyleAttributeName
                      value:@(NSUnderlineStyleSingle)
                      range:(NSRange){0,1}];
    [tncString addAttribute:NSUnderlineColorAttributeName value:[UIColor clearColor] range:NSMakeRange(0, 1)];


    [tncString addAttribute:NSUnderlineStyleAttributeName
                      value:@(NSUnderlineStyleSingle)
                      range:(NSRange){5,[tncString length] - 5}];

    [tncBtn setAttributedTitle:tncString forState:UIControlStateNormal];

---

UIUnderlinedButton.h

@interface UIUnderlinedButton : UIButton {

}


+ (UIUnderlinedButton*) underlinedButton;
@end

UIUnderlinedButton.m

@implementation UIUnderlinedButton

+ (UIUnderlinedButton*) underlinedButton {
    UIUnderlinedButton* button = [[UIUnderlinedButton alloc] init];
    return [button autorelease];
}

- (void) drawRect:(CGRect)rect {
    CGRect textRect = self.titleLabel.frame;

    // need to put the line at top of descenders (negative value)
    CGFloat descender = self.titleLabel.font.descender;

    CGContextRef contextRef = UIGraphicsGetCurrentContext();

    // set to same colour as text
    CGContextSetStrokeColorWithColor(contextRef, self.titleLabel.textColor.CGColor);

    CGContextMoveToPoint(contextRef, textRect.origin.x, textRect.origin.y + textRect.size.height + descender);

    CGContextAddLineToPoint(contextRef, textRect.origin.x + textRect.size.width, textRect.origin.y + textRect.size.height + descender);

    CGContextClosePath(contextRef);

    CGContextDrawPath(contextRef, kCGPathStroke);
}


@end

---

您可以在界面构建器本身中执行此操作。

选择属性检查器将标题类型从普通更改为属性

https://i.stack.imgur.com/kM4YA.png

设置适当的字体大小和文本对齐方式

https://i.stack.imgur.com/aBcfS.png

然后选择标题文本并将字体设置为下划线

https://i.stack.imgur.com/j7kc7.png

---

属性字符串非常简单

创建具有设置属性的字典并应用于属性字符串。然后你可以将属性字符串设置为 uibutton 中的 attibutedtitle 或 uilabel 中的属性文本。

NSDictionary *attrDict = @{NSFontAttributeName : [UIFont
 systemFontOfSize:14.0],NSForegroundColorAttributeName : [UIColor
 whiteColor]};
 NSMutableAttributedString *title =[[NSMutableAttributedString alloc] initWithString:@"mybutton" attributes: attrDict]; 
[title addAttribute:NSUnderlineStyleAttributeName value:[NSNumber numberWithInteger:NSUnderlineStyleSingle] range:NSMakeRange(0,[commentString length])]; [btnRegLater setAttributedTitle:title forState:UIControlStateNormal];

---

这是我的函数，适用于 Swift 1.2。

func underlineButton(button : UIButton, text: String) {

    var titleString : NSMutableAttributedString = NSMutableAttributedString(string: text)
    titleString.addAttribute(NSUnderlineStyleAttributeName, value: NSUnderlineStyle.StyleSingle.rawValue, range: NSMakeRange(0, count(text.utf8)))
    button.setAttributedTitle(titleString, forState: .Normal)
}

更新 Swift 3.0 扩展：

extension UIButton {
    func underlineButton(text: String) {
        let titleString = NSMutableAttributedString(string: text)
        titleString.addAttribute(NSUnderlineStyleAttributeName, value: NSUnderlineStyle.styleSingle.rawValue, range: NSMakeRange(0, text.characters.count))
        self.setAttributedTitle(titleString, for: .normal)
    }
}

---

截至 2019 年 9 月在 Xcode 10.3 中运行的 Swift 5.0 版本：

extension UIButton {
  func underlineText() {
    guard let title = title(for: .normal) else { return }

    let titleString = NSMutableAttributedString(string: title)
    titleString.addAttribute(
      .underlineStyle,
      value: NSUnderlineStyle.single.rawValue,
      range: NSRange(location: 0, length: title.count)
    )
    setAttributedTitle(titleString, for: .normal)
  }
}

要使用它，首先使用 button.setTitle("Button Title", for: .normal) 设置按钮标题，然后调用 button.underlineText() 使该标题带有下划线。

---

尼克的回答是一个很好的、快速的方法。

我在 drawRect 中添加了对阴影的支持。

如果您的按钮标题在文本下方有阴影，尼克的回答没有考虑到：

https://i.stack.imgur.com/e618S.png

但是您可以将下划线向下移动阴影的高度，如下所示：

CGFloat descender = self.titleLabel.font.descender;
CGContextRef contextRef = UIGraphicsGetCurrentContext();
CGFloat shadowHeight = self.titleLabel.shadowOffset.height;
descender += shadowHeight;

然后你会得到这样的东西：

https://i.stack.imgur.com/8y3hS.png

---

对于 Swift 3，可以使用以下扩展：

extension UIButton {
    func underlineButton(text: String) {
        let titleString = NSMutableAttributedString(string: text)
        titleString.addAttribute(NSUnderlineStyleAttributeName, value: NSUnderlineStyle.styleSingle.rawValue, range: NSMakeRange(0, text.characters.count))
        self.setAttributedTitle(titleString, for: .normal)
    }
}

---

// Only override drawRect: if you perform custom drawing.
// An empty implementation adversely affects performance during animation.
- (void)drawRect:(CGRect)rect {
CGRect textRect = self.titleLabel.frame;

// need to put the line at top of descenders (negative value)
CGFloat descender = self.titleLabel.font.descender;

CGContextRef contextRef = UIGraphicsGetCurrentContext();
UIColor *colr;
// set to same colour as text
if (self.isHighlighted || self.isSelected) {
    colr=self.titleLabel.highlightedTextColor;
}
else{
    colr= self.titleLabel.textColor;
}
CGContextSetStrokeColorWithColor(contextRef, colr.CGColor);

CGContextMoveToPoint(contextRef, textRect.origin.x, textRect.origin.y +        textRect.size.height + descender);

CGContextAddLineToPoint(contextRef, textRect.origin.x + textRect.size.width, textRect.origin.y + textRect.size.height + descender);

CGContextClosePath(contextRef);

CGContextDrawPath(contextRef, kCGPathStroke);
}
//Override this to change the underline color to highlighted color
-(void)setHighlighted:(BOOL)highlighted
{
[super setHighlighted:highlighted];
// [self setNeedsDisplay];
}

---

扩展@Nick H247 的答案，我遇到了一个问题，首先当按钮在旋转时调整大小时下划线没有重绘；这可以通过将按钮设置为重绘来解决，如下所示：

myButton.contentMode = UIViewContentModeRedraw; 

当边界改变时，这会强制按钮重绘。

其次，原始代码假设您在按钮中只有 1 行文本（我的按钮在旋转时换行为 2 行），并且下划线仅出现在文本的最后一行。可以修改 drawRect 代码以首先计算按钮中的行数，然后在每一行而不是底部添加下划线，如下所示：

 - (void) drawRect:(CGRect)rect {
CGRect textRect = self.titleLabel.frame;

// need to put the line at top of descenders (negative value)
CGFloat descender = self.titleLabel.font.descender;

CGContextRef contextRef = UIGraphicsGetCurrentContext();

// set to same colour as text
CGContextSetStrokeColorWithColor(contextRef, self.titleLabel.textColor.CGColor);

CGSize labelSize = [self.titleLabel.text sizeWithFont:self.titleLabel.font
                            constrainedToSize:self.titleLabel.frame.size
                                lineBreakMode:UILineBreakModeWordWrap];

CGSize labelSizeNoWrap = [self.titleLabel.text sizeWithFont:self.titleLabel.font forWidth:self.titleLabel.frame.size.width lineBreakMode:UILineBreakModeMiddleTruncation ];

int numberOfLines = abs(labelSize.height/labelSizeNoWrap.height);

for(int i = 1; i<=numberOfLines;i++) {
 //        Original code
 //        CGContextMoveToPoint(contextRef, textRect.origin.x, textRect.origin.y + textRect.size.height + descender + PADDING);
 //        
 //        CGContextAddLineToPoint(contextRef, textRect.origin.x + textRect.size.width, textRect.origin.y + textRect.size.height + descender);

    CGContextMoveToPoint(contextRef, textRect.origin.x, textRect.origin.y + (labelSizeNoWrap.height*i) + descender + PADDING);

    CGContextAddLineToPoint(contextRef, textRect.origin.x + textRect.size.width, textRect.origin.y + (labelSizeNoWrap.height*i) + descender);

    CGContextClosePath(contextRef);

    CGContextDrawPath(contextRef, kCGPathStroke);

}


}

希望这段代码对其他人有帮助！

---

迅速

func underlineButton(button : UIButton) {

var titleString : NSMutableAttributedString = NSMutableAttributedString(string: button.titleLabel!.text!)
titleString.addAttribute(NSUnderlineStyleAttributeName, value: NSUnderlineStyle.StyleSingle.rawValue, range: NSMakeRange(0, button.titleLabel!.text!.utf16Count))
button.setAttributedTitle(titleString, forState: .Normal)}

---

您可以使用此代码在按钮中添加带间距的下划线。

当我试图从界面生成器中绘制下划线时。它看起来像下图。

1 - 界面生成器参考

https://i.stack.imgur.com/NLaxr.png

在使用下面的代码后，我得到了我想要的结果。

2 - 使用描述的代码

https://i.stack.imgur.com/wN333.png

public func setTextUnderline()
    {
        let dummyButton: UIButton = UIButton.init()
        dummyButton.setTitle(self.titleLabel?.text, for: .normal)
        dummyButton.titleLabel?.font = self.titleLabel?.font
        dummyButton.sizeToFit()

        let dummyHeight = dummyButton.frame.size.height + 3

        let bottomLine = CALayer()
        bottomLine.frame = CGRect.init(x: (self.frame.size.width - dummyButton.frame.size.width)/2, y: -(self.frame.size.height - dummyHeight), width: dummyButton.frame.size.width, height: 1.0)
        bottomLine.backgroundColor = self.titleLabel?.textColor.cgColor
        self.layer.addSublayer(bottomLine)
    }

---

当我们按住一个带下划线的按钮时，将如何处理这种情况？在这种情况下，按钮的文本颜色会根据突出显示的颜色而变化，但线条保持原始颜色。假设如果正常状态下的按钮文本颜色为黑色，则其下划线也将具有黑色。该按钮的突出显示颜色为白色。按住按钮将按钮文本颜色从黑色更改为白色，但下划线颜色保持黑色。

---

我相信这是 XCode 字体编辑器中的一些错误。如果您使用界面生成器，则必须将标题从普通更改为属性，打开 TextEdit 创建带下划线的文本并复制粘贴到 XCode 中的文本框

---

尼克 H247 的回答，但 Swift 方法：

import UIKit

class UnderlineUIButton: UIButton {

    override func drawRect(rect: CGRect) {
        super.drawRect(rect)

        let textRect = self.titleLabel!.frame

        var descender = self.titleLabel?.font.descender

        var contextRef: CGContextRef = UIGraphicsGetCurrentContext();

        CGContextSetStrokeColorWithColor(contextRef, self.titleLabel?.textColor.CGColor);

        CGContextMoveToPoint(contextRef, textRect.origin.x, textRect.origin.y + textRect.size.height + descender!);

        CGContextAddLineToPoint(contextRef, textRect.origin.x + textRect.size.width, textRect.origin.y + textRect.size.height + descender!);

        CGContextClosePath(contextRef);

        CGContextDrawPath(contextRef, kCGPathStroke);
    }
}

---

func underline(text: String, state: UIControlState = .normal, color:UIColor? = nil) {
        var titleString = NSMutableAttributedString(string: text)

        if let color = color {
            titleString = NSMutableAttributedString(string: text,
                               attributes: [NSForegroundColorAttributeName: color])
        }

        let stringRange = NSMakeRange(0, text.characters.count)
        titleString.addAttribute(NSUnderlineStyleAttributeName,
                                 value: NSUnderlineStyle.styleSingle.rawValue,
                                 range: stringRange)

        self.setAttributedTitle(titleString, for: state)
    }

---

@NickH247's 答案的 Swift 3 版本，带有自定义下划线颜色、线宽和间隙：

import Foundation

class UnderlinedButton: UIButton {

    private let underlineColor: UIColor
    private let thickness: CGFloat
    private let gap: CGFloat

    init(underlineColor: UIColor, thickness: CGFloat, gap: CGFloat, frame: CGRect? = nil) {
        self.underlineColor = underlineColor
        self.thickness = thickness
        self.gap = gap
        super.init(frame: frame ?? .zero)
    }

    override func draw(_ rect: CGRect) {
        super.draw(rect)

        guard let textRect = titleLabel?.frame,
            let decender = titleLabel?.font.descender,
            let context = UIGraphicsGetCurrentContext() else { return }

        context.setStrokeColor(underlineColor.cgColor)
        context.move(to: CGPoint(x: textRect.origin.x, y: textRect.origin.y + textRect.height + decender + gap))
        context.setLineWidth(thickness)
        context.addLine(to: CGPoint(x: textRect.origin.x + textRect.width, y: textRect.origin.y + textRect.height + decender + gap))
        context.closePath()
        context.drawPath(using: .stroke)
    }

    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

---