根据其原始纯文本状态创建UIButton属性标题

Question

我正在尝试创建UIButton的子类，该子类强制执行文本字距调整。 因此，当我在Interface Builder中构建按钮时，设置文本颜色（使用纯文本），希望能够从纯titleLabel实例中获取现有文本，颜色，段落样式和字体并将其转换为具有相同属性的属性标签。

我写了两类我认为可能会有所帮助的类别：

+ (NSMutableAttributedString*)attributedStringWithTitle:(NSString*)title fromExistingAttributedString:(NSAttributedString*)attributedString
{
    NSDictionary *attributes = [attributedString attributesAtIndex:0 effectiveRange:NULL];
    return [[NSMutableAttributedString alloc] initWithString:title attributes:attributes];
}

+ (NSMutableAttributedString*)attributedStringWithTitle:(NSString*)title fromPlainTextLabel:(UILabel*)label
{
    NSMutableAttributedString* mutableTitle = [[NSMutableAttributedString alloc] initWithString:title];
    [mutableTitle addAttribute:NSFontAttributeName value:label.font range:[mutableTitle fullRange]];
    [mutableTitle addAttribute:NSForegroundColorAttributeName value:label.textColor range:[mutableTitle fullRange]];
    NSMutableParagraphStyle *style = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
    style.alignment = label.textAlignment;
    [mutableTitle addAttribute:NSParagraphStyleAttributeName value:style range:[mutableTitle fullRange]];
    return mutableTitle;
}

然后在我的UIButton子类中，我像这样重写这些：

- (void)setAttributedTitle:(NSAttributedString *)title forState:(UIControlState)state
{
    NSMutableAttributedString* mutableTitle = [title mutableCopy];
    [mutableTitle addAttributes:@{NSKernAttributeName: @(kDefaultKerning)} range:[mutableTitle fullRange]];
    [super setAttributedTitle:mutableTitle forState:state];
    [self setNeedsDisplay];
}

- (void)setTitle:(NSString *)title forState:(UIControlState)state
{
    NSMutableAttributedString* mutableTitle;
    if ([self attributedTitleForState:state]) {
        mutableTitle = [NSMutableAttributedString attributedStringWithTitle:title fromExistingAttributedString:[self attributedTitleForState:state]];
    } else {
        mutableTitle = [NSMutableAttributedString attributedStringWithTitle:title fromPlainTextLabel:self.titleLabel];
    }
    [self setAttributedTitle:mutableTitle forState:state];    
}

但是有些东西不起作用-特别要注意的是， [self attributedTitleForState:state]和[self titleForState:state]总是[self titleForState:state] 。 在我看来，在Interface Builder中设置属性的方式有些脱节，因为当文本通过OK传递时，所有样式都丢失了。

Answer 1

终于可以工作了。 原来，纯文本UIButton的多个属性位于多个位置。 有些具有直接从UIButton检索的帮助方法，有些则没有。

• 字体： self.titleLabel.font （无辅助方法）
• 颜色： [self titleColorForState:state]
• 文字： [self titleForState:state]
• 归属文本： [self attributedTitleForState]

纯文本UIButton默认情况下不具有任何文本对齐方式，因为它是由内容水平对齐方式控制的 。

因此，我更改了辅助方法（第一个是相同的，但是我不得不更改了第二个）：

+ (NSMutableAttributedString*)attributedStringWithTitle:(NSString*)title fromExistingAttributedString:(NSAttributedString*)attributedString
{
    NSDictionary *attributes = [attributedString attributesAtIndex:0 effectiveRange:NULL];
    return [[NSMutableAttributedString alloc] initWithString:title attributes:attributes];
}

+ (NSMutableAttributedString*)attributedStringWithTitle:(NSString*)title font:(UIFont*)font color:(UIColor*)color 
{
    NSMutableAttributedString* mutableTitle = [[NSMutableAttributedString alloc] initWithString:title];
    [mutableTitle addAttribute:NSFontAttributeName value:font range:[mutableTitle fullRange]];
    [mutableTitle addAttribute:NSForegroundColorAttributeName value:color range:[mutableTitle fullRange]];
    NSMutableParagraphStyle *style = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
    [mutableTitle addAttribute:NSParagraphStyleAttributeName value:style range:[mutableTitle fullRange]];
    return mutableTitle;
}

我已经实现了这样的：

- (void)setAttributedTitle:(NSAttributedString *)title forState:(UIControlState)state
{
    NSMutableAttributedString* mutableTitle = [title mutableCopy];
    [mutableTitle addAttributes:@{NSKernAttributeName: @(kDefaultKerning)} range:[mutableTitle fullRange]];
    [super setAttributedTitle:mutableTitle forState:state];
    [self setNeedsDisplay];
}

- (void)setTitle:(NSString *)title forState:(UIControlState)state
{
    NSMutableAttributedString* mutableTitle;
    if ([self attributedTitleForState:state]) {
        mutableTitle = [NSMutableAttributedString attributedStringWithTitle:title fromExistingAttributedString:[self attributedTitleForState:state]];
    } else {
        mutableTitle = [NSMutableAttributedString attributedStringWithTitle:title font:self.titleLabel.font color:[self titleColorForState:state]];
    }
    [self setAttributedTitle:mutableTitle forState:state];
}