在UITextView中处理NSAttributedString的UIContentSizeCategoryDidChangeNotification

Question

我在UITextView中有一个NSAttributedString,并且在处理动态类型时特别是文本样式时想要处理UIContentSizeCategoryDidChangeNotification.我见过的所有示例(IntroToTextKitDemo)都解决了整个UI元素的字体相同的情况.有谁知道如何正确处理这个所以所有属性都正确更新？

注意:当iOS 7在NDA下时,我在开发者论坛上问过这个问题.我在这里发布它是因为我找到了一个解决方案,并认为其他人可能会发现它很有用.

Answer 1

我找到了解决方案.处理通知时,您需要遍历属性并查找文本样式并更新字体:

- (void)preferredContentSizeChanged:(NSNotification *)aNotification
{
    UITextView *textView = <the text view holding your attributed text>

    NSMutableAttributedString *attributedString = [[NSMutableAttributedString alloc] initWithAttributedString:textView.attributedText];
    NSRange range = NSMakeRange(0, attributedString.length - 1);

    // Walk the string's attributes
    [attributedString enumerateAttributesInRange:range options:NSAttributedStringEnumerationReverse usingBlock:
     ^(NSDictionary *attributes, NSRange range, BOOL *stop) {

         // Find the font descriptor which is based on the old font size change
         NSMutableDictionary *mutableAttributes = [NSMutableDictionary dictionaryWithDictionary:attributes];
         UIFont *font = mutableAttributes[@"NSFont"];
         UIFontDescriptor *fontDescriptor = font.fontDescriptor;

         // Get the text style and get a new font descriptor based on the style and update font size
         id styleAttribute = [fontDescriptor objectForKey:UIFontDescriptorTextStyleAttribute];
         UIFontDescriptor *newFontDescriptor = [UIFontDescriptor preferredFontDescriptorWithTextStyle:styleAttribute];

         // Get the new font from the new font descriptor and update the font attribute over the range
         UIFont *newFont = [UIFont fontWithDescriptor:newFontDescriptor size:0.0];
         [attributedString addAttribute:NSFontAttributeName value:newFont range:range];
     }];

    textView.attributedText = attributedString;
}