如何从 NSMutableAttributeString 获取 NSParagraphStyleAttributeName？

Question

我创建了一个 NSMutableAttributedString 对齐方式如下：

UIFont * font =  [UIFont systemFontOfSize:[UIFont labelFontSize]];
/// Make a copy of the default paragraph style
NSMutableParagraphStyle *paragraphStyle = [[NSParagraphStyle defaultParagraphStyle] mutableCopy];
/// Set line break mode
paragraphStyle.lineBreakMode = NSLineBreakByWordWrapping;
/// Set text alignment
paragraphStyle.alignment = alignmentForString(textString) ;//NSTextAlignmentLeft;//NSTextAlignmentRight;// NSTextAlignmentNatural;//  NSTextAlignmentLeft;

NSDictionary *messageDrawRectAttributesDictionary = @{
                        NSFontAttributeName: font,
                        NSParagraphStyleAttributeName: paragraphStyle,
                        NSForegroundColorAttributeName:[UIColor blackColor]
                        };

NSMutableAttributedString * mutalbleAttributedString = [[NSMutableAttributedString alloc] initWithString:textString attributes:messageDrawRectAttributesDictionary];

我想知道（以后在应用程序中使用）如何获得我在此字符串中设置的对齐方式。

我试过这段代码，但没有完全理解我在做什么：

NSRange range = NSMakeRange(0,mutalbleAttributedString.length-1);
NSDictionary * paraDic =[mutalbleAttributedString attribute:NSParagraphStyleAttributeName atIndex:0 longestEffectiveRange:&range inRange:range];

现在，我搜索了很多示例代码并阅读了 Apple 文档。但没有运气。我得到空字典。

我唯一需要的帮助是，如果有人可以编写正确的代码，将 return 比对数据给我。

Answer 1

当您调用 attribute:atIndex:longestEffectiveRange:inRange: 时，return 值是所请求属性的值，而不是字典。另外，不要为两个范围参数传入 range。

你的代码应该是这样的：

NSRange range = NSMakeRange(0, mutalbleAttributedString.length);
NSParagraphStyle *paraStyle = [mutalbleAttributedString attribute:NSParagraphStyleAttributeName atIndex:0 longestEffectiveRange:NULL inRange:range];
NSTextAlignment alignment = paraStyle.alignment;

注意以下变化：

所请求属性的正确 return 值
为 range
将 NULL 传递给 longestEffectiveRange:，因为您不关心该值。

Answer 2

您可以像这样从 NSMutableAttributedString 中获取对齐方式：

 NSRange range = NSMakeRange(0, mutableAttributedString.length);
 NSDictionary *attributes = [mutableAttributedString attributesAtIndex:0 effectiveRange:&range];
 NSMutableParagraphStyle *paragraphStyle = attributes[NSParagraphStyleAttributeName];
 NSTextAlignment alignment = paragraphStyle.alignment;

Answer 3

Swift 5 示例：

var effectiveRange = NSMakeRange(0, attributedString.length)
let currentParagraphStyle: NSParagraphStyle = attributedText?.attribute(NSAttributedString.Key.paragraphStyle, at: 0, effectiveRange: &effectiveRange) as! NSParagraphStyle
let align = currentParagraphStyle.alignment
let lineSpacing = currentParagraphStyle.lineSpacing
let newParagraphStyle = currentParagraphStyle.lineHeightMultiple

如何从 NSMutableAttributeString 获取 NSParagraphStyleAttributeName？

How to get NSParagraphStyleAttributeName from NSMutableAttributeString?

objective-c

nsattributedstring

nsmutableattributedstring