如何将 NSMutableParagraphStyle 中的第一行加粗？

Question

我有一个名为 "rectangle" 的 class 来制作自定义 UILabel。我在矩形 class 中覆盖了 "draw"。当我实例化标签时，我希望第一行文本以粗体显示。我知道如何通过手动获取每个字符串的范围来解决这个问题......但是，我有 300 多个字符串要做。这些字符串当前位于一个数组中，格式如下："Happy \n Birthday"。我怎样才能把 "Happy" 这个词加粗？

var messageText = "Happy \n Birthday"
let rectanglePath = UIBezierPath(rect: rectangleRect)
context.saveGState()
UIColor.white.setFill()
rectanglePath.fill()
context.restoreGState()

darkPurple.setStroke()
rectanglePath.lineWidth = 0.5
rectanglePath.lineCapStyle = .square
rectanglePath.lineJoinStyle = .round
rectanglePath.stroke()

let rectangleStyle = NSMutableParagraphStyle()
rectangleStyle.alignment = .center
let rectangleFontAttributes = [
  .font: UIFont.myCustomFont(true),
  .foregroundColor: UIColor.black,
  .paragraphStyle: rectangleStyle,
  ] as [NSAttributedString.Key: Any]

let rectangleTextHeight: CGFloat = messageText.boundingRect(with: CGSize(width: rectangleRect.width, height: CGFloat.infinity), options: .usesLineFragmentOrigin, attributes: rectangleFontAttributes, context: nil).height
context.saveGState()
context.clip(to: rectangleRect)
messageText.draw(in: CGRect(x: rectangleRect.minX, y: rectangleRect.minY + (rectangleRect.height - rectangleTextHeight) / 2, width: rectangleRect.width, height: rectangleTextHeight), withAttributes: rectangleFontAttributes)
context.restoreGState()

Answer 1

您可以通过 newline:

分隔字符串来找到第一个

let firstLine = "Happy \n Birthday".split(separator: "\n").first

这将为您提供字符串的第一行。（长文本多行不算）然后你可以使用它找到范围并应用粗体效果。

这是如何工作的：

您需要按照接受多行的方式设置标签：
找到第一行的范围
转换为nsRange
将属性应用于范围

这是一个完整的示例：

import UIKit
import PlaygroundSupport

extension StringProtocol where Index == String.Index {

    func nsRange(from range: Range<Index>) -> NSRange {
        return NSRange(range, in: self)
    }
}

class MyViewController : UIViewController {
    override func loadView() {
        let view = UIView()
        view.backgroundColor = .white

        let label = UILabel()
        label.numberOfLines = 0
        label.text = "Happy \n Birthday"
        label.textColor = .black

        let text = "Happy \n Birthday"
        let attributedString = NSMutableAttributedString(string: text)
        let firstLine = text.split(separator: "\n").first!
        let range = text.range(of: firstLine)!
        attributedString.addAttributes([.font : UIFont.boldSystemFont(ofSize: 14)], range: text.nsRange(from: range))
        label.attributedText = attributedString
        label.sizeToFit()

        view.addSubview(label)
        self.view = view
    }
}

PlaygroundPage.current.liveView = MyViewController()

如何将 NSMutableParagraphStyle 中的第一行加粗？

How do you bold the first line in an NSMutableParagraphStyle?

ios

swift

uilabel

nsattributedstring

nsrange