根據其原始純文本狀態創建UIButton屬性標題

Question

我正在嘗試創建UIButton的子類，該子類強制執行文本字距調整。 因此，當我在Interface Builder中構建按鈕時，設置文本顏色（使用純文本），希望能夠從純titleLabel實例中獲取現有文本，顏色，段落樣式和字體並將其轉換為具有相同屬性的屬性標簽。

我寫了兩類我認為可能會有所幫助的類別：

+ (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子類中，我像這樣重寫這些：

- (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];    
}

但是有些東西不起作用-特別要注意的是， [self attributedTitleForState:state]和[self titleForState:state]總是[self titleForState:state] 。 在我看來，在Interface Builder中設置屬性的方式有些脫節，因為當文本通過OK傳遞時，所有樣式都丟失了。

Answer 1

終於可以工作了。 原來，純文本UIButton的多個屬性位於多個位置。 有些具有直接從UIButton檢索的幫助方法，有些則沒有。

• 字體： self.titleLabel.font （無輔助方法）
• 顏色： [self titleColorForState:state]
• 文字： [self titleForState:state]
• 歸屬文本： [self attributedTitleForState]

純文本UIButton默認情況下不具有任何文本對齊方式，因為它是由內容水平對齊方式控制的 。

因此，我更改了輔助方法（第一個是相同的，但是我不得不更改了第二個）：

+ (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;
}

我已經實現了這樣的：

- (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];
}