How to set kerning in iPhone UILabel

问题:

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];

回答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];

回答2:

Before:

After:

Here's a Swift 2 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 ?? "").characters.count)
            guard let kern = attributedText?.attribute(NSKernAttributeName, 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(NSKernAttributeName, 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.

回答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];
}

回答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

回答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()

回答6:

An example using IBDesignables and IBInspectables where you can manage to set the kerning value through storyboard only. I found it very practical and I thought to share it with you.

UILabelKerning.h

#import <UIKit/UIKit.h>

IB_DESIGNABLE

@interface UILabelKerning : UILabel
@property (assign, nonatomic) IBInspectable int kerning;
@end

UILabelKerning.m

#import "UILabelKerning.h"

@implementation UILabelKerning


-(void)awakeFromNib {

    [self setTheAttributes];
}

- (id)initWithCoder:(NSCoder*)aDecoder
{
    self = [super initWithCoder:aDecoder];
    if (self)
    {
        // Initialization code
    }

    return self;
}
-(void)setTheAttributes{
    NSMutableAttributedString *attributedString =[[NSMutableAttributedString alloc] initWithAttributedString:self.attributedText];
    [attributedString addAttribute:NSKernAttributeName
                             value:[NSNumber numberWithFloat:self.kerning]
                             range:NSMakeRange(0, [self.text length])];
    [self setAttributedText:attributedString];
}
@end

回答7:

As far as I am aware, UILabel will not render the characteristics of NSAttributedString. There are a couple of nice open source solutions. I recently used TTTAttributedLabel as a swap in replacement for UILabel that accepts NSAttributedString.

DTCoreText (former NSAttributedString+HTML) is also getting a bit of buzz lately.

回答8:

In Swift 2.0...

Add an extension:

extension UIView {
    func attributes(font: String, color: UIColor, fontSize: CGFloat, kern: Double) -> [String: NSObject] {
        let attribute = [
            NSForegroundColorAttributeName: color,
            NSKernAttributeName: kern,
            NSFontAttributeName : UIFont(name: font, size: fontSize)!
        ]
        return attribute
    }
}

Now, just set your UILabel as attributedText:

self.label.attributedText = NSMutableAttributedString(string: "SwiftExample", attributes: attributes("SourceSans-Regular", color: UIColor.whiteColor(), fontSize: 20, kern: 2.0))   

Obviously, I added a bunch of parameters that you may not need. Play around -- feel free to rewrite the method -- I was looking for this on a bunch of different answers so figured I'd post the whole extension in case it helps someone out there... -rab