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];