How to set kerning in iPhone UILabel

Question

I am developing an iPhone app, and I want to set kerning in UILabel. The code I've written (possibly around kCTKernAttributeName) seems to be in error. How might I approach fixing this?

NSMutableAttributedString *attStr;   
NSString *str = @"aaaaaaa";    
CFStringRef kern = kCTKernAttributeName;        
NSNumber *num = [NSNumber numberWithFloat: 2.0f];    
NSDictionary *attributesDict = [NSDictionary dictionaryWithObject:num 
forKey:(NSString*)kern];        
[attStr initWithString:str attributes:attributesDict];      
CGRect frame1 = CGRectMake(0, 0, 100, 40);    
UILabel *label1 = [[UILabel alloc] initWithFrame:frame1];    
label1.text = attStr    
[self.view addSubview:label1];

Solution 1

Old question, but you can do it now (easily).

NSMutableAttributedString *attributedString;
attributedString = [[NSMutableAttributedString alloc] initWithString:@"Please get wider"];
[attributedString addAttribute:NSKernAttributeName value:@5 range:NSMakeRange(10, 5)];
[self.label setAttributedText:attributedString];

For Nov 2013, Just to expand on this great answer, here's some totally typical code. Usually you'd set the font as well. Note in the comments the old-fashioned way using ordinary old .text. Hope it helps someone

NSString *yourText = @"whatever";

UILabel* label = [[UILabel alloc] initWithFrame:CGRectMake(0,0,0,0)];

// simple approach with no tracking...
// label.text = yourText;
// [label setFont:[UIFont fontWithName:@"HelveticaNeue-Light" size:24]];

NSMutableAttributedString *attributedString;

attributedString = [[NSMutableAttributedString alloc] initWithString:yourText];

[attributedString addAttribute:NSKernAttributeName
                         value:[NSNumber numberWithFloat:2.0]
                         range:NSMakeRange(0, [yourText length])];

[attributedString addAttribute:NSFontAttributeName
                         value:[UIFont fontWithName:@"HelveticaNeue-Light" size:24]
                         range:NSMakeRange(0, [yourText length])];

label.attributedText = attributedString;

label.textColor = [UIColor blackColor];
label.backgroundColor = [UIColor clearColor];
label.textAlignment = NSTextAlignmentCenter;

[label sizeToFit];

Solution 2

Before:

After:

Here's a Swift 3 extension that let's you set a UILabel's kerning via code or storyboard:

extension UILabel {

    @IBInspectable var kerning: Float {
        get {
            var range = NSMakeRange(0, (text ?? "").count)
            guard let kern = attributedText?.attribute(NSAttributedStringKey.kern, at: 0, effectiveRange: &range),
                let value = kern as? NSNumber
                else {
                    return 0
            }
            return value.floatValue
        }
        set {
            var attText:NSMutableAttributedString

            if let attributedText = attributedText {
                attText = NSMutableAttributedString(attributedString: attributedText)
            } else if let text = text {
                attText = NSMutableAttributedString(string: text)
            } else {
                attText = NSMutableAttributedString(string: "")
            }

            let range = NSMakeRange(0, attText.length)
            attText.addAttribute(NSAttributedStringKey.kern, value: NSNumber(value: newValue), range: range)
            self.attributedText = attText
        }
    }
}

Demo usage:

myLabel.kerning = 3.0

or

The demo uses 3.0 kerning for drama, but I've found 0.1 - 0.8 tends to work well in practice.

Solution 3

Taking DBD's answer, I made a category on UILabel which allows setting the kerning if running on iOS6+ with graceful fall back to just setting text on previous iOS versions. Might be of help to others...

UILabel+TextKerning.h

#import <UIKit/UIKit.h>

@interface UILabel (TextKerning)

/**
 * Set the label's text to the given string, using the given kerning value if able.
 * (i.e., if running on iOS 6.0+). The kerning value specifies the number of points
 * by which to adjust spacing between characters (positive values increase spacing,
 * negative values decrease spacing, a value of 0 is default)
 **/
- (void) setText:(NSString *)text withKerning:(CGFloat)kerning;

/**
 * Set the kerning value of the currently-set text.  The kerning value specifies the number of points
 * by which to adjust spacing between characters (positive values increase spacing,
 * negative values decrease spacing, a value of 0 is default)
 **/
- (void) setKerning:(CGFloat)kerning;

@end

UILabel+TextKerning.m

#import "UILabel+TextKerning.h"

@implementation UILabel (TextKerning)

-(void) setText:(NSString *)text withKerning:(CGFloat)kerning
{
    if ([self respondsToSelector:@selector(setAttributedText:)])
    {
        NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithString:text];
        [attributedString addAttribute:NSKernAttributeName
                                 value:[NSNumber numberWithFloat:kerning]
                                 range:NSMakeRange(0, [text length])];
        [self setAttributedText:attributedString];
    }
    else
        [self setText:text];
}

-(void) setKerning:(CGFloat)kerning
{
    [self setText:self.text withKerning:kerning];
}

Solution 4

Just to be up-to-date here, iOS 6 introduced attributedText for UILabel and UITextView!

UILabel reference:
http://developer.apple.com/library/ios/#documentation/uikit/reference/UILabel_Class/Reference/UILabel.html#//apple_ref/occ/instp/UILabel/attributedText

Solution 5

Just do this in Swift:

    let myTitle = "my title"
    let titleLabel = UILabel()
    let attributes: NSDictionary = [
        NSFontAttributeName:UIFont(name: "HelveticaNeue-Light", size: 20),
        NSForegroundColorAttributeName:UIColor.whiteColor(),
        NSKernAttributeName:CGFloat(2.0)
    ]
    let attributedTitle = NSAttributedString(string: myTitle, attributes: attributes as? [String : AnyObject])

    titleLabel.attributedText = attributedTitle
    titleLabel.sizeToFit()

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