在UITextView中处理NSAttributedString的UIContentSizeCategoryDidChangeNotification

Question

我在UITextView中有一个NSAttributedString，希望在使用动态类型并特别处理文本样式时，能够处理UIContentSizeCategoryDidChangeNotification。我看到的所有示例（IntroToTextKitDemo）都解决了字体在整个UI元素中是相同的情况。有人知道如何正确处理这种情况，以使所有属性都正确更新吗？

注：我曾在iOS 7保密协议下向开发者论坛提出过此问题。我在这里发布它，因为我找到了解决方案，认为其他人可能会发现它有用。

- byamabe

Answer 1

我找到了一个解决方案。在处理通知时，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;
}

- byamabe

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谢谢，非常有用。方法的第三行应该是NSRange range = NSMakeRange(0, attributedString.length);以覆盖整个文本。 - Smilin Brian