iOS/Objective-C UILabel text kerning

问题

I was in search of how to increase character spacing in UILabels to make more attractive my UI Design implementations for the Apps I do. And I found following answer, which tells it allows to adjust the Text Kerning, and it's written in Swift.

But what I needed is an Objective-C Solution. So I tried to convert the following code snippet:

import UIKit
@IBDesignable
class KerningLabel: UILabel {
    @IBInspectable var kerning:CGFloat = 0.0{
        didSet{
            if ((self.attributedText?.length) != nil)
            {
                let attribString = NSMutableAttributedString(attributedString: self.attributedText!)
                attribString.addAttributes([NSKernAttributeName:kerning], range:NSMakeRange(0, self.attributedText!.length))
                self.attributedText = attribString
            }
        }
    }
}

to following in Objective-C:
KerningLabel.h:

#import <UIKit/UIKit.h>
IB_DESIGNABLE
@interface KerningLabel : UILabel
@property (nonatomic) IBInspectable CGFloat kerning;
@end

KerningLabel.m:

#import "KerningLabel.h"

@implementation KerningLabel
@synthesize kerning;
- (void) setAttributedText:(NSAttributedString *)attributedText {
    if ([self.attributedText length] > 0) {
        NSMutableAttributedString *muAttrString = [[NSMutableAttributedString alloc] initWithAttributedString:self.attributedText];
        [muAttrString addAttribute:NSKernAttributeName value:@(self.kerning) range:NSMakeRange(0, [self.attributedText length])];
        self.attributedText = muAttrString;
    }
}
@end

And it gives the following Attribute in XCode IB to adjust the Kerning,

But it really doesn't seems to be taking effect on the UI when the App is running and also in the Interface Builder the text goes disappearing.

Please somebody help me and point out what I have done wrong.

Thanks in Advanced!

回答1:

You want to update your attributedText every time kerning is updated. So, your .h should look like:

IB_DESIGNABLE
@interface KerningLabel : UILabel

@property (nonatomic) IBInspectable CGFloat kerning;

@end

and your .m :

@implementation KerningLabel

- (void)setKerning:(CGFloat)kerning
{
    _kerning = kerning;

    if(self.attributedText)
    {
        NSMutableAttributedString *attribString = [[NSMutableAttributedString alloc]initWithAttributedString:self.attributedText];
        [attribString addAttribute:NSKernAttributeName value:@(kerning) range:NSMakeRange(0, self.attributedText.length)];
        self.attributedText = attribString;
     }
}

@end

来源：https://stackoverflow.com/questions/37826749/ios-objective-c-uilabel-text-kerning

标签

ios

objective-c

fonts

interface-builder

uilabel