UILabel 字体下方加下划线

UILabel *knowKankan = [[UILabel alloc] initWithFrame:CGRectMake(0, MAINHEIGHT - 78 , MAINWIDTH, 22)];

knowKankan.textAlignment = NSTextAlignmentCenter;

knowKankan.textColor = [UIColor whiteColor];

knowKankan.font = [UIFont systemFontOfSize:16];

NSMutableAttributedString *content = [[NSMutableAttributedString alloc]initWithString:[NSString stringWithFormat:@"了解看看"]];

NSRange contentRange = {0,[content length]};

[content addAttribute:NSUnderlineStyleAttributeName value:[NSNumber numberWithInteger:NSUnderlineStyleSingle] range:contentRange];

knowKankan.attributedText = content;

[imageTwo addSubview:knowKankan]