Underline text in UIlabel - ios

Question

How can I underline a text that could be multiple lines of string?
I find some people suggest UIWebView, but it is obviously too heavy a class for just text rendering.
My thoughts was to figure out the start point and length of each string in each line.
And draw a line under it accordingly.
I meet problems at how to figure out the length and start point for the string.
I tried to use -[UILabel textRectForBounds:limitedToNumberOfLines:], this should be the drawing bounding rect for the text right?
Then I have to work on the alignment?
How can I get the start point of each line when it is center-justified and right justified?

Answer 1

You may subclass from UILabel and override drawRect method:
- (void)drawRect:(CGRect)rect {
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSetRGBStrokeColor(ctx, 207.0f/255.0f, 91.0f/255.0f, 44.0f/255.0f, 1.0f); // RGBA
CGContextSetLineWidth(ctx, 1.0f);
CGContextMoveToPoint(ctx, 0, self.bounds.size.height - 1);
CGContextAddLineToPoint(ctx, self.bounds.size.width, self.bounds.size.height - 1);
CGContextStrokePath(ctx);
[super drawRect:rect];
}
UPD:
As of iOS 6 Apple added NSAttributedString support for UILabel, so now it's much easier and works for multiple lines:
NSDictionary *underlineAttribute = #{NSUnderlineStyleAttributeName: #(NSUnderlineStyleSingle)};
myLabel.attributedText = [[NSAttributedString alloc] initWithString:#"Test string"
attributes:underlineAttribute];
If you still wish to support iOS 4 and iOS 5, I'd recommend to use TTTAttributedLabel rather than underline label manually. However if you need to underline one-line UILabel and don't want to use third-party components, code above would still do the trick.

Answer 2

In Swift:
let underlineAttriString = NSAttributedString(string: "attriString",
attributes: [NSAttributedString.Key.underlineStyle: NSUnderlineStyle.single.rawValue])
label.attributedText = underlineAttriString

Answer 3

This is what i did. It works like butter.
1) Add CoreText.framework to your Frameworks.
2) import <CoreText/CoreText.h> in the class where you need underlined label.
3) Write the following code.
NSMutableAttributedString *attString = [[NSMutableAttributedString alloc] initWithString:#"My Messages"];
[attString addAttribute:(NSString*)kCTUnderlineStyleAttributeName
value:[NSNumber numberWithInt:kCTUnderlineStyleSingle]
range:(NSRange){0,[attString length]}];
self.myMsgLBL.attributedText = attString;
self.myMsgLBL.textColor = [UIColor whiteColor];

Answer 4

Use an attribute string:
NSMutableAttributedString* attrString = [[NSMutableAttributedString alloc] initWithString:#"Your String"]
[attrString addAttribute:(NSString*)kCTUnderlineStyleAttributeName
value:[NSNumber numberWithInt:kCTUnderlineStyleSingle]
range:(NSRange){0,[attrString length]}];
And then override the label - (void)drawTextInRect:(CGRect)aRect and render the text in something like:
CGContextRef ctx = UIGraphicsGetCurrentContext();
CGContextSaveGState(ctx);
CTFramesetterRef framesetter = CTFramesetterCreateWithAttributedString((CFAttributedStringRef)attrString);
drawingRect = self.bounds;
CGMutablePathRef path = CGPathCreateMutable();
CGPathAddRect(path, NULL, drawingRect);
textFrame = CTFramesetterCreateFrame(framesetter,CFRangeMake(0,0), path, NULL);
CGPathRelease(path);
CFRelease(framesetter);
CTFrameDraw(textFrame, ctx);
CGContextRestoreGState(ctx);
Or better yet instead of overriding just use the OHAttributedLabel created by Olivier Halligon

Answer 5

I've combined some of provided answers, to create better (at least for my requirements) UILabel subclass, which supports:
multiline text with various label bounds (text can be in the middle of label frame, or accurate size)
underline
strikeout
underline/strikeout line offset
text alignment
different font sizes
https://github.com/GuntisTreulands/UnderLineLabel

Answer 6

People, who do not want to subclass the view (UILabel/UIButton) etc...
'forgetButton' can be replace by any lable too.
-(void) drawUnderlinedLabel {
NSString *string = [forgetButton titleForState:UIControlStateNormal];
CGSize stringSize = [string sizeWithFont:forgetButton.titleLabel.font];
CGRect buttonFrame = forgetButton.frame;
CGRect labelFrame = CGRectMake(buttonFrame.origin.x + buttonFrame.size.width - stringSize.width,
buttonFrame.origin.y + stringSize.height + 1 ,
stringSize.width, 2);
UILabel *lineLabel = [[UILabel alloc] initWithFrame:labelFrame];
lineLabel.backgroundColor = [UIColor blackColor];
//[forgetButton addSubview:lineLabel];
[self.view addSubview:lineLabel];
}

Answer 7

NSString *tem =self.detailCustomerCRMCaseLabel.text;
if (tem != nil && ![tem isEqualToString:#""]) {
NSMutableAttributedString *temString=[[NSMutableAttributedString alloc]initWithString:tem];
[temString addAttribute:NSUnderlineStyleAttributeName
value:[NSNumber numberWithInt:1]
range:(NSRange){0,[temString length]}];
self.detailCustomerCRMCaseLabel.attributedText = temString;
}

Answer 8

Another solution could be (since iOS 7) given a negative value to NSBaselineOffsetAttributeName, for example your NSAttributedString could be:
NSAttributedString *attributedText = [[NSAttributedString alloc] initWithString:#"my text goes here'
attributes:#{NSFontAttributeName: [UIFont fontWithName:#"Helvetica-Regular" size:12],
NSForegroundColorAttributeName: [UIColor blackColor],
NSUnderlineStyleAttributeName: #(NSUnderlineStyleSingle), NSBaselineOffsetAttributeName: #(-3)}];
Hope this will help ;-)

Answer 9

NSMutableAttributedString *text = [self.myUILabel.attributedText mutableCopy];
[text addAttribute:NSUnderlineStyleAttributeName value:#(NSUnderlineStyleSingle) range:NSMakeRange(0, text.length)];
self.myUILabel.attributedText = text;

Answer 10

You can create a custom label with name UnderlinedLabel and edit drawRect function.
#import "UnderlinedLabel.h"
#implementation UnderlinedLabel
- (void)drawRect:(CGRect)rect
{
NSString *normalTex = self.text;
NSDictionary *underlineAttribute = #{NSUnderlineStyleAttributeName: #(NSUnderlineStyleSingle)};
self.attributedText = [[NSAttributedString alloc] initWithString:normalTex
attributes:underlineAttribute];
[super drawRect:rect];
}

Answer 11

Here is the easiest solution which works for me without writing additional codes.
// To underline text in UILable
NSMutableAttributedString *text = [[NSMutableAttributedString alloc] initWithString:#"Type your text here"];
[text addAttribute:NSUnderlineStyleAttributeName value:#(NSUnderlineStyleSingle) range:NSMakeRange(0, text.length)];
lblText.attributedText = text;

Answer 12

Sometimes we developer stuck in small designing part of any UI screen. One of the most irritating requirement is under line text. Don’t worry here is the solution.
Underlining a text in a UILabel using Objective C
UILabel *label=[[UILabel alloc]initWithFrame:CGRectMake(0, 0, 320, 480)];
label.backgroundColor=[UIColor lightGrayColor];
NSMutableAttributedString *attributedString;
attributedString = [[NSMutableAttributedString alloc] initWithString:#"Apply Underlining"];
[attributedString addAttribute:NSUnderlineStyleAttributeName value:#1 range:NSMakeRange(0,
[attributedString length])];
[label setAttributedText:attributedString];
Underlining a text in UILabel using Swift
label.backgroundColor = .lightGray
let attributedString = NSMutableAttributedString.init(string: "Apply UnderLining")
attributedString.addAttribute(NSUnderlineStyleAttributeName, value: 1, range:
NSRange.init(location: 0, length: attributedString.length))
label.attributedText = attributedString

Answer 13

An enhanced version of the code of Kovpas (color and line size)
#implementation UILabelUnderlined
- (void)drawRect:(CGRect)rect {
CGContextRef ctx = UIGraphicsGetCurrentContext();
const CGFloat* colors = CGColorGetComponents(self.textColor.CGColor);
CGContextSetRGBStrokeColor(ctx, colors[0], colors[1], colors[2], 1.0); // RGBA
CGContextSetLineWidth(ctx, 1.0f);
CGSize tmpSize = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(200, 9999)];
CGContextMoveToPoint(ctx, 0, self.bounds.size.height - 1);
CGContextAddLineToPoint(ctx, tmpSize.width, self.bounds.size.height - 1);
CGContextStrokePath(ctx);
[super drawRect:rect];
}
#end

Answer 14

I have Created for multiline uilabel with underline :
For Font size 8 to 13 set int lineHeight = self.font.pointSize+3;
For font size 14 to 20 set int lineHeight = self.font.pointSize+4;
- (void)drawRect:(CGRect)rect
{
CGContextRef ctx = UIGraphicsGetCurrentContext();
const CGFloat* colors = CGColorGetComponents(self.textColor.CGColor);
CGContextSetRGBStrokeColor(ctx, colors[0], colors[1], colors[2], 1.0); // RGBA
CGContextSetLineWidth(ctx, 1.0f);
CGSize tmpSize = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(self.frame.size.width, 9999)];
int height = tmpSize.height;
int lineHeight = self.font.pointSize+4;
int maxCount = height/lineHeight;
float totalWidth = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(1000, 9999)].width;
for(int i=1;i<=maxCount;i++)
{
float width=0.0;
if((i*self.frame.size.width-totalWidth)<=0)
width = self.frame.size.width;
else
width = self.frame.size.width - (i* self.frame.size.width - totalWidth);
CGContextMoveToPoint(ctx, 0, lineHeight*i-1);
CGContextAddLineToPoint(ctx, width, lineHeight*i-1);
}
CGContextStrokePath(ctx);
[super drawRect:rect];
}

Answer 15

Swift 4.1 ver:
let underlineAttriString = NSAttributedString(string:"attriString", attributes:
[NSAttributedStringKey.underlineStyle: NSUnderlineStyle.styleSingle.rawValue])
label.attributedText = underlineAttriString

Answer 16

As kovpas has shown you can use the bounding box in most cases, although it is not always guaranteed that the bounding box will fit neatly around the text. A box with a height of 50 and font size of 12 may not give the results you want depending on the UILabel configuration.
Query the UIString within the UILabel to determine its exact metrics and use these to better place your underline regardless of the enclosing bounding box or frame using the drawing code already provided by kovpas.
You should also look at UIFont's "leading" property that gives the distance between baselines based on a particular font. The baseline is where you would want your underline to be drawn.
Look up the UIKit additions to NSString:
(CGSize)sizeWithFont:(UIFont *)font
//Returns the size of the string if it were to be rendered with the specified font on a single line.
(CGSize)sizeWithFont:(UIFont *)font constrainedToSize:(CGSize)size
// Returns the size of the string if it were rendered and constrained to the specified size.
(CGSize)sizeWithFont:(UIFont *)font constrainedToSize:(CGSize)size lineBreakMode:(UILineBreakMode)lineBreakMode
//Returns the size of the string if it were rendered with the specified constraints.

Answer 17

I use an open source line view and just added it to the button subviews:
UILabel *label = termsButton.titleLabel;
CGRect frame = label.frame;
frame.origin.y += frame.size.height - 1;
frame.size.height = 1;
SSLineView *line = [[SSLineView alloc] initWithFrame:frame];
line.lineColor = [UIColor lightGrayColor];
[termsButton addSubview:line];
This was inspired by Karim above.

Answer 18

Based on Kovpas & Damien Praca's Answers, here is an implementation of UILabelUnderligned which also support textAlignemnt.
#import <UIKit/UIKit.h>
#interface UILabelUnderlined : UILabel
#end
and the implementation:
#import "UILabelUnderlined.h"
#implementation DKUILabel
- (id)initWithFrame:(CGRect)frame
{
self = [super initWithFrame:frame];
if (self) {
// Initialization code
}
return self;
}
- (void)drawRect:(CGRect)rect {
CGContextRef ctx = UIGraphicsGetCurrentContext();
const CGFloat* colors = CGColorGetComponents(self.textColor.CGColor);
CGContextSetRGBStrokeColor(ctx, colors[0], colors[1], colors[2], 1.0); // RGBA
CGContextSetLineWidth(ctx, 1.0f);
CGSize textSize = [self.text sizeWithFont:self.font constrainedToSize:CGSizeMake(200, 9999)];
// handle textAlignement
int alignementXOffset = 0;
switch (self.textAlignment) {
case UITextAlignmentLeft:
break;
case UITextAlignmentCenter:
alignementXOffset = (self.frame.size.width - textSize.width)/2;
break;
case UITextAlignmentRight:
alignementXOffset = self.frame.size.width - textSize.width;
break;
}
CGContextMoveToPoint(ctx, alignementXOffset, self.bounds.size.height - 1);
CGContextAddLineToPoint(ctx, alignementXOffset+textSize.width, self.bounds.size.height - 1);
CGContextStrokePath(ctx);
[super drawRect:rect];
}
#end

Answer 19

Here's another, simpler solution (underline's width is not most accurate but it was good enough for me)
I have a UIView (_view_underline) that has White background, height of 1 pixel and I update its width everytime I update the text
// It's a shame you have to do custom stuff to underline text
- (void) underline {
float width = [[_txt_title text] length] * 10.0f;
CGRect prev_frame = [_view_underline frame];
prev_frame.size.width = width;
[_view_underline setFrame:prev_frame];
}

Answer 20

NSUnderlineStyleAttributeName which takes an NSNumber (where 0 is no underline) can be added to an attribute dictionary.
I don't know if this is any easier. But, it was easier for my purposes.
NSDictionary *attributes;
attributes = #{NSFontAttributeName:font, NSParagraphStyleAttributeName: style, NSUnderlineStyleAttributeName:[NSNumber numberWithInteger:1]};
[text drawInRect:CGRectMake(self.contentRect.origin.x, currentY, maximumSize.width, textRect.size.height) withAttributes:attributes];

Answer 21

You can use this my custom label!
You can also use interface builder to set
import UIKit
class YHYAttributedLabel : UILabel{
#IBInspectable
var underlineText : String = ""{
didSet{
self.attributedText = NSAttributedString(string: underlineText,
attributes: [NSAttributedString.Key.underlineStyle: NSUnderlineStyle.single.rawValue])
}
}
}