NSAttributedString 项目符号列表问题

Question

我正在尝试使用 NSAttributedString 和 UITextView 创建项目符号列表。而且，这是我到目前为止能够实现的目标：

可以看到，两条线之间有一个小的"shift"。这是我用来构建属性字符串的代码片段：

func add(bulletList strings: [String],
         indentation: CGFloat = 15,
         lineSpacing: CGFloat = 3,
         paragraphSpacing: CGFloat = 10) {

    func createParagraphAttirbute() -> NSParagraphStyle {
        var paragraphStyle: NSMutableParagraphStyle
        let nonOptions = NSDictionary() as! [NSTextTab.OptionKey: Any]

        paragraphStyle = NSParagraphStyle.default.mutableCopy() as! NSMutableParagraphStyle
        paragraphStyle.tabStops = [
            NSTextTab(textAlignment: .left, location: indentation, options: nonOptions)]
        paragraphStyle.defaultTabInterval = indentation
        paragraphStyle.firstLineHeadIndent = 0
        paragraphStyle.lineSpacing = lineSpacing
        paragraphStyle.paragraphSpacing = paragraphSpacing
        paragraphStyle.headIndent = indentation
        return paragraphStyle
    }

    var buffer = NSMutableAttributedString.init()

    for string in strings {
        let formattedString = "\u{2022} \(string)\n"
        let attributedString = NSMutableAttributedString(string: formattedString)
        let paragraphStyle = createParagraphAttirbute()

        attributedString.addAttributes(
            [NSAttributedStringKey.paragraphStyle : paragraphStyle],
            range: NSMakeRange(0, attributedString.length))

        attributedString.addAttributes(
            textAttributes,
            range: NSMakeRange(0, attributedString.length))

        let string:NSString = NSString(string: formattedString)
        let rangeForBullet:NSRange = string.range(of: bulletPoint)
        attributedString.addAttributes(bulletAttirbutes, range: rangeForBullet)
        buffer.append(attributedString)
    }
}

您认为所选段落参数有问题吗？因为代码几乎完成了预期的工作，排除了这个差距。

更新 1

按照@the4kman 的建议，我更改了提供的代码，如下所示：

paragraphStyle.firstLineHeadIndent = indentation

但现在我的所有线条都对齐了，包括要点：

更新 2

好的，解决方法很简单——将 space 替换为制表符。请参阅下面的更新代码。

Answer 1

@the4kman，@Krunal，感谢您的回复！解决方案甚至更简单。在 let formattedString = "\u{2022} \(string)\n 中用 \t 替换 space 符号可以得到有效的缩进。

为了完整性，完整的解决方案代码是（只替换一个字符）：

func add(bulletList strings: [String],
         font: UIFont,
         indentation: CGFloat = 15,
         lineSpacing: CGFloat = 3,
         paragraphSpacing: CGFloat = 10,
         textColor: UIColor = .black,
         bulletColor: UIColor = .red) -> NSAttributedString {

    func createParagraphAttirbute() -> NSParagraphStyle {
        var paragraphStyle: NSMutableParagraphStyle
        let nonOptions = NSDictionary() as! [NSTextTab.OptionKey: Any]

        paragraphStyle = NSParagraphStyle.default.mutableCopy() as! NSMutableParagraphStyle
        paragraphStyle.tabStops = [
            NSTextTab(textAlignment: .left, location: indentation, options: nonOptions)]
        paragraphStyle.defaultTabInterval = indentation
        paragraphStyle.firstLineHeadIndent = 0
        paragraphStyle.lineSpacing = lineSpacing
        paragraphStyle.paragraphSpacing = paragraphSpacing
        paragraphStyle.headIndent = indentation
        return paragraphStyle
    }

    let bulletPoint = "\u{2022}"
    let textAttributes: [NSAttributedStringKey: Any] = [.font: font, .foregroundColor: textColor]
    let bulletAttributes: [NSAttributedStringKey: Any] = [.font: font, .foregroundColor: bulletColor]
    let buffer = NSMutableAttributedString.init()

    for string in strings {
        let formattedString = "\(bulletPoint)\t\(string)\n"
        let attributedString = NSMutableAttributedString(string: formattedString)
        let paragraphStyle = createParagraphAttirbute()

        attributedString.addAttributes(
            [NSAttributedStringKey.paragraphStyle : paragraphStyle],
            range: NSMakeRange(0, attributedString.length))

        attributedString.addAttributes(
            textAttributes,
            range: NSMakeRange(0, attributedString.length))

        let string:NSString = NSString(string: formattedString)
        let rangeForBullet:NSRange = string.range(of: bulletPoint)
        attributedString.addAttributes(bulletAttributes, range: rangeForBullet)
        buffer.append(attributedString)
    }

    return buffer
}

Answer 2

这是一个简单的 Objective-C 片段，主要基于已接受的答案：

NSString* text = 
            "•\tSome text for bullet 1.\n"
            "•\tSome text for bullet 2.\n"
            "•\tSome text for bullet 3."

UIFont* bodyFont = [UIFont preferredFontForTextStyle: UIFontTextStyleBody];
CGFloat indentSize = bodyFont.pointSize;
NSMutableParagraphStyle *paraStyle = [[[NSMutableParagraphStyle alloc] init];
paraStyle.alignment = NSTextAlignmentLeft;
paraStyle.tabStops = @[ [[[NSTextTab alloc] initWithTextAlignment:NSTextAlignmentLeft location:indentSize options:@{}] ];
paraStyle.defaultTabInterval = indentSize;
paraStyle.headIndent = indentSize;
paraStyle.firstLineHeadIndent = 0;
paraStyle.lineHeightMultiple = 0.85;
paraStyle.lineSpacing = 0;
paraStyle.paragraphSpacing = bodyFont.lineHeight * 0.25;
paraStyle.paragraphSpacingBefore = 0;
[atrStr appendAttributedString:
 [[[NSMutableAttributedString alloc] initWithString:avc.message attributes:@{
      NSParagraphStyleAttributeName:paraStyle,
      NSFontAttributeName: bodyFont,
  }]];

NSAttributedString 项目符号列表问题

NSAttributedString bullet list issues

uitextview

nsattributedstring

ios

swift

更新 1

更新 2