添加NSMutableParagraphStyle lineSpacing导致文本不适合UILabel

Question

我已经创建了一个普通的UILabel，并希望能够添加行间距到文本，这到UILabel。

虽然当我这样做时，它会影响adjustsFontSizeToFitWidth，并且它不再适合UILabel。

我用过的一些代码：

        var userQuestionsAnswer = UILabel(frame: CGRectMake(0, 0, 20, 20))
        userQuestionsAnswer.font = UIFont(name: Font.GothamBlack, size: 15)
        userQuestionsAnswer.numberOfLines = 0
        userQuestionsAnswer.adjustsFontSizeToFitWidth = true

        var style = NSMutableParagraphStyle()
        style.lineSpacing = view.frame.size.height * 0.021
        style.alignment = NSTextAlignment.Center
        let attributes = [NSParagraphStyleAttributeName : style]
        var answerText = "This is the answer"

        self.userQuestionsAnswer.attributedText = NSAttributedString(string: answerText!, attributes:attributes)

有没有人能告诉我为什么会这样，以及我是如何解决的？

Answer 1

卸下NSMutableParagraphStyle即可正常工作。我不知道为什么，但是这个属性是破坏文本字体大小调整的原因。

Answer 2

可能的解决方案是：

1. 设置与paragraphStyle相关的属性(lineHeightMultiplier、对齐等)在storyboard\xib；(在更改label;
2. create属性的属性文本之前，将paragrapshStyle属性添加到所需的属性；将attributedString;
3. set attributedString添加为attributedText属性。

在不使用任何语法的情况下，它可能如下所示：

    func paragraphStyle(in attrString: NSAttributedString?) -> NSParagraphStyle? {
        return attrString?.attribute(NSParagraphStyleAttributeName, at: 0, effectiveRange: nil) as? NSParagraphStyle
    }

    let text = "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book."

    let attributedText = NSMutableAttributedString(string: text, attributes: [
        NSFontAttributeName: UIFont.systemFont(ofSize: 20.0),
        NSForegroundColorAttributeName: UIColor.orange
    ])

    if let paragraphStyle = paragraphStyle(in: label.attributedText) {
        let textRange = NSMakeRange(0, text.characters.count)
        attributedText.addAttribute(NSParagraphStyleAttributeName, value: paragraphStyle, range: textRange)
    }

    label.attributedText = attributedText

使用pod 'SwiftyAttributes‘和NSMutableAttributedString扩展：

import SwiftyAttributes

extension NSMutableAttributedString {
    func withParagraphStyle(from attrString: NSAttributedString?) -> NSMutableAttributedString {
        guard let attrString = attrString, let pStyle = attrString.attribute(.paragraphStyle, at: 0) else {
            return self
        }

        return self.withAttribute(pStyle)
    }
}

代码将为：

    let text = "Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book."

    label.attributedText = text.withAttributes([
            .font(.systemFont(ofSize: 20.0)),
            .textColor(.orange)
        ]).withParagraphStyle(from: label.attributedText)