关于UILabel和UIButton有的时候需要添加下划线，一般有两种方式通过默认的NSMutableAttributedString设置，第二种就是在drawRect中画一条下划线，本文就简单的选择第一种，第二种有兴趣的可以自己研究一下。
UILabel设置下划线:
UILabel *label = [[UILabel alloc] initWithFrame:CGRectMake(10, 100, 310, 50)];
label.backgroundColor = [UIColor redColor];
[label setLineBreakMode:NSLineBreakByWordWrapping];
label.numberOfLines =3;
[label setFont:[UIFont systemFontOfSize:14]];
NSMutableAttributedString *content = [[NSMutableAttributedString alloc]initWithString:[NSString stringWithFormat:@"博文地址:http://www.cnblogs.com/xiaofeixiang 博客园-FlyElephant QQ群:228407086"]];
NSRange contentRange = {0,[content length]};
[content addAttribute:NSUnderlineStyleAttributeName value:[NSNumber numberWithInteger:NSUnderlineStyleSingle] range:contentRange];
label.attributedText = content;
[self.view addSubview:label];
UIButton设置下划线:
UIButton *button=[[UIButton alloc]initWithFrame:CGRectMake(10, 200, 80, 30)];
NSMutableAttributedString *title = [[NSMutableAttributedString alloc] initWithString:@"FlyElephant"];
NSRange titleRange = {0,[title length]};
[title addAttribute:NSUnderlineStyleAttributeName value:[NSNumber numberWithInteger:NSUnderlineStyleSingle] range:titleRange];
[button setAttributedTitle:title
forState:UIControlStateNormal];
[button setBackgroundColor:[UIColor redColor]];
[button.titleLabel setFont:[UIFont systemFontOfSize:14]];
[self.view addSubview:button];
最终效果如下:
原文：http://www.cnblogs.com/xiaofeixiang/p/4582292.html