Swift中如何为Attributed String设置前两行自定义间距、第三行保持段落样式

你需要为AttributedString的不同文本范围设置不同的段落样式即可实现需求，具体实现如下：

适配硬换行场景（你的现有代码场景，文本带\n分隔每行） #

let myString = "Your account phone numbers are listed here.\nTo change or delete a phone number, tap on it.\nTo add a phone number, go to the top right-hand corner of your screen and tap on “Add”."
let font = UIFont.systemFont(ofSize: 14)
let attributedString = NSMutableAttributedString(string: myString, attributes: [.font: font])

// 定义两种段落样式
let spacedParagraphStyle = NSMutableParagraphStyle()
spacedParagraphStyle.lineSpacing = 8 // 可根据设计要求调整行间距数值
spacedParagraphStyle.lineBreakMode = .byWordWrapping

let normalParagraphStyle = NSMutableParagraphStyle()
normalParagraphStyle.lineBreakMode = .byWordWrapping

// 拆分文本获取每行对应的范围
let lineParts = myString.components(separatedBy: .newlines)
guard lineParts.count >= 3 else {
    displayLabel.attributedText = attributedString
    return
}
let firstLineRange = NSRange(location: 0, length: lineParts[0].count + 1) // +1计入换行符
let secondLineRange = NSRange(location: firstLineRange.upperBound, length: lineParts[1].count + 1)
let thirdLineRange = NSRange(location: secondLineRange.upperBound, length: lineParts[2].count)

// 给对应范围设置段落属性
attributedString.addAttribute(.paragraphStyle, value: spacedParagraphStyle, range: firstLineRange)
attributedString.addAttribute(.paragraphStyle, value: spacedParagraphStyle, range: secondLineRange)
attributedString.addAttribute(.paragraphStyle, value: normalParagraphStyle, range: thirdLineRange)

displayLabel.attributedText = attributedString

适配自动折行场景（无硬换行符，依赖Label宽度自动换行） #

如果你的文本没有手动插入\n，需要先通过文本布局计算每行对应的范围，再设置属性：

// 接上文创建的attributedString
displayLabel.sizeToFit()
let labelWidth = displayLabel.bounds.width

// 构建文本布局计算行范围
let textStorage = NSTextStorage(attributedString: attributedString)
let layoutManager = NSLayoutManager()
textStorage.addLayoutManager(layoutManager)
let textContainer = NSTextContainer(size: CGSize(width: labelWidth, height: .greatestFiniteMagnitude))
textContainer.lineFragmentPadding = 0
textContainer.maximumNumberOfLines = 0
layoutManager.addTextContainer(textContainer)

var lineRanges: [NSRange] = []
var currentIndex = 0
while currentIndex < myString.utf16.count {
    let lineRange = layoutManager.lineFragmentRange(forGlyphAt: currentIndex, effectiveRange: nil)
    lineRanges.append(lineRange)
    currentIndex = NSMaxRange(lineRange)
}

// 给前两行设置行间距，剩余行用默认样式
if lineRanges.count >= 2 {
    attributedString.addAttribute(.paragraphStyle, value: spacedParagraphStyle, range: lineRanges[0])
    attributedString.addAttribute(.paragraphStyle, value: spacedParagraphStyle, range: lineRanges[1])
}
if lineRanges.count >= 3 {
    for i in 2..<lineRanges.count {
        attributedString.addAttribute(.paragraphStyle, value: normalParagraphStyle, range: lineRanges[i])
    }
}

displayLabel.attributedText = attributedString

内容的提问来源于stack exchange，提问作者iOSDuDe