Underlining text in UIButton

To use interface builder to underline, one has to:

Change it to attributed

Highlight the text in the Attributes inspector

Right click, choose Font and then Underline

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

Video someone else made https://www.youtube.com/watch?v=5-ZnV3jQd9I

From iOS6 it is now possible to use an NSAttributedString to perform underlining (and anything else attributed strings support) in a much more flexible way:

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];

Note: added this as another answer - as its a totally different solution to my previous one.

Edit: oddly (in iOS8 at least) you have to underline the first character otherwise it doesn't work!

so as a workaround, set the first char underlined with clear colour!

    // 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

You can do it in the interface builder itself.

Select the attribute inspector Change the title type from plain to attributed

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

Set appropriate font size and text alignment

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

Then select the title text and set the font as underlined

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

It is very simple with attributed string

Creates a dictionary with set attributes and apply to the attributed string. Then you can set the attributed string as attibutedtitle in uibutton or attributedtext in uilabel.

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];

Here is my function, works in 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)
}

UPDATE Swift 3.0 extension:

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)
    }
}

The Swift 5.0 version that works as of September 2019 in Xcode 10.3:

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)
  }
}

To use it, set your button title first with button.setTitle("Button Title", for: .normal) and then call button.underlineText() to make that title underlined.

Nick's answer is a great, quick way to do this.

I added support in drawRect for shadows.

Nick's answer doesn't take into account if your button title has a shadow below the text:

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

But you can move the underline down by the height of the shadow like so:

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

Then you'll get something like this:

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

For Swift 3 the following extension can be used:

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];
}

Expanding on the answer by @Nick H247, I experienced an issue where firstly the underline was not redrawing when the button resized on rotation; this can be solved by setting your button to redraw like so:

myButton.contentMode = UIViewContentModeRedraw; 

This forces the button to redraw when the bounds change.

Secondly, the original code assumed you only had 1 line of text in the button (my button wraps to 2 lines on rotation) and the underline only appears on the last line of text. The drawRect code can be modified to first calculate the number of lines in the button, then put an underline on every line rather than just the bottom, like so:

 - (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);

}


}

Hope this code helps someone else!

In swift

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)}

You can use this code to add underline with spacing in button.

When I tried to draw an underline from interface builder. It look like below image.

1 - Interface builder reference

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

And after using below code I achieved the result as I wanted.

2 - using described code

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)
    }

How will one handle the case when we keep a button underlined pressed? In that case the button's textcolor changes according to highlighted color but line remains of original color. Let say if button text color in normal state is black then its underline will also have black color. The button's highlighted color is white. Keeping button pressed changes button text color from black to white but underline color remains black.

I believe it's some bug in font editor in XCode. If you using interface builder you have to change title from Plain to Attributed, open TextEdit create underlined text and copy-paste to textbox in XCode

Nick H247's answer but Swift approach:

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)
    }

Swift 3 version for @NickH247's answer with custom underline color, linewidth and gap:

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")
    }
}