Objective c 中的 UIButton 虚线下划线

正常下划线有效，但点下划线似乎不起作用？

UIButton *btn = [UIButton buttonWithType:UIButtonTypeCustom]; 
btn.frame = CGRectMake(100, 10, 300, 300);
NSMutableAttributedString *titleString = [[NSMutableAttributedString alloc] initWithString:@"Durga Vundavalli"];

// making text property to underline text-
[titleString addAttribute:NSUnderlineStyleAttributeName value:[NSNumber numberWithInteger:NSUnderlineStyleSingle] range:NSMakeRange(0, [titleString length])];

// using text on button
[btn setAttributedTitle: titleString forState:UIControlStateNormal];
[self.view addSubview:btn];

以下是文档中的枚举：

typedef NS_ENUM(NSInteger, NSUnderlineStyle) {
    NSUnderlineStyleNone                                = 0x00,
    NSUnderlineStyleSingle                              = 0x01,
    NSUnderlineStyleThick NS_ENUM_AVAILABLE_IOS(7_0)    = 0x02,
    NSUnderlineStyleDouble NS_ENUM_AVAILABLE_IOS(7_0)   = 0x09,

    NSUnderlinePatternSolid NS_ENUM_AVAILABLE_IOS(7_0)      = 0x0000,
    NSUnderlinePatternDot NS_ENUM_AVAILABLE_IOS(7_0)        = 0x0100,
    NSUnderlinePatternDash NS_ENUM_AVAILABLE_IOS(7_0)       = 0x0200,
    NSUnderlinePatternDashDot NS_ENUM_AVAILABLE_IOS(7_0)    = 0x0300,
    NSUnderlinePatternDashDotDot NS_ENUM_AVAILABLE_IOS(7_0) = 0x0400,

    NSUnderlineByWord NS_ENUM_AVAILABLE_IOS(7_0) = 0x8000
}

你不能只放NSUnderlinePatternDot。如果你想要 2 行点怎么办？你必须使用一个Pattern and a Style.

[titleString addAttribute:NSUnderlineStyleAttributeName value:[NSNumber numberWithInteger:(NSUnderlinePatternDot|NSUnderlineStyleSingle)] range:NSMakeRange(0, [titleString length])];

正如医生所说，您必须使用口罩：

讨论
样式、模式和可选的字掩码进行“或”运算 共同创造价值NSUnderlineStyleAttributeName and NSStrikethroughStyleAttributeName.