自定义带下划线文本的UIButton

最新推荐文章于 2017-04-30 17:51:29 发布

转载最新推荐文章于 2017-04-30 17:51:29 发布 · 2.9k 阅读

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本文详细介绍了如何在iOS中通过自定义UIUnderlinedButton类来实现在按钮文本上的下划线效果，并针对有阴影的文本进行了优化。

摘选自：http://stackoverflow.com/questions/2630004/underlining-text-in-uibutton

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);
}

上述代码没有考虑显示文本有阴影的情况，下面的的代码做这个处理：

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