限制支持的动态类型字体大小

Question

我想支持动态类型但仅限于某个限制,类似于Settings.app,其中标准UITableViewCells可以增长UIContentSizeCategoryAccessibilityExtraExtraLarge但不大.

有没有一种简单的方法来实现标准的UITableViewCell样式？

Answer 1

我在 UIFont 上使用自定义类别来获得具有限制的首选字体，如下所示

extension UIFont {

  static func preferredFont(withTextStyle textStyle: UIFont.TextStyle, maxSize: CGFloat) -> UIFont {
    // Get the descriptor
    let fontDescriptor = UIFontDescriptor.preferredFontDescriptor(withTextStyle: textStyle)

    // Return a font with the minimum size
    return UIFont(descriptor: fontDescriptor, size: min(fontDescriptor.pointSize, maxSize))
  }

}

对象

@implementation UIFont (preferredFontWithSizeLimit)

+ (UIFont *)preferredFontWithTextStyle:(UIFontTextStyle)style maxSize:(CGFloat)maxSize {
    // Get the descriptor
    UIFontDescriptor *fontDescriptor = [UIFontDescriptor preferredFontDescriptorWithTextStyle: style];

    // Return a font with the minimum size
    return [UIFont fontWithDescriptor: fontDescriptor size: MIN(fontDescriptor.pointSize, maxSize)];
}

@end

要根据样式对限制进行硬编码，您可以添加这样的内容（我将每种样式的当前系统默认值放在注释中）

+ (UIFont *)limitedPreferredFontForTextStyle:(UIFontTextStyle)style {
    // Create a table of size limits once
    static NSDictionary *sizeLimitByStyle;
    static dispatch_once_t once_token;
    dispatch_once(&once_token, ^{
        sizeLimitByStyle = @{
            UIFontTextStyleTitle1: @56, // default 28
            UIFontTextStyleTitle2: @44, // default 22
            UIFontTextStyleTitle3: @40, // default 20
            UIFontTextStyleHeadline: @34, // default 17
            UIFontTextStyleSubheadline: @30, // default 15
            UIFontTextStyleBody: @34, // default 17
            UIFontTextStyleCallout: @32, // default 16
            UIFontTextStyleFootnote: @26, // default 13
            UIFontTextStyleCaption1: @24, // default 12
            UIFontTextStyleCaption2: @22, // default 11
        };
    });
    
    // Look up the size limit
    CGFloat maxSize = INFINITY;
    NSNumber *limit = sizeLimitByStyle[style];
    if (limit) {
        maxSize = limit.doubleValue;
    }
    // Return the font
    return [UIFont preferredFontWithTextStyle: style maxSize: maxSize];
}