找出一个字符串中有多少个字符可以放在一行中

Question

我必须根据每行可以容纳多少个字符将字符串拆分为一个数组。数组中的每个对象只需一行文本。我能够计算字符串中的行数，但我不知道如何找出一行中的最大字符数。

func lineCount(forText text: String) -> Int {
        let font = UIFont.systemFont(ofSize: 24.0)
        let width: Int = Int(self.tableView.frame.size.width)
        let rect: CGRect = text.boundingRect(with: CGSize(width: CGFloat(width), height: CGFloat(MAXFLOAT)), options: .usesLineFragmentOrigin, attributes: [NSAttributedStringKey.font: font], context: nil)
        return Int(ceil(rect.size.height / font.lineHeight))
    }

Answer 1

Swift 5 更新对我有用的答案。

1. 已添加lineBreakMode

extension String {    
    func splittingLinesThatFitIn(width: CGFloat, font: UIFont) -> [String] {
        
        let paragraphStyle = NSMutableParagraphStyle()
        paragraphStyle.lineBreakMode = .byWordWrapping
        
        // set up styled text for the container
        let storage = NSTextStorage(string: self, attributes: [
            NSAttributedString.Key.font: font,
            NSAttributedString.Key.paragraphStyle: paragraphStyle
        ])
        
        // add a layout manage for the storage
        let layout = NSLayoutManager()
        storage.addLayoutManager(layout)
        
        // Set up the size of the container
        // width is what we care about, height is maximum
        let container = NSTextContainer(size: CGSize(width: width, height: CGFloat.greatestFiniteMagnitude))
        
        // add the container to the layout
        layout.addTextContainer(container)
        
        var lines = [String]()
        
        // generate the layout and add each line to the array
        layout.enumerateLineFragments(forGlyphRange: NSMakeRange(0, storage.length)) { _, _, _, range, _ in
            lines.append(storage.attributedSubstring(from: range).string)
        }
        
        debugPrint(lines)
        
        return lines
    }
}

Answer 2

由于某些字体具有可变宽度的字符，因此您无法在每种字体中获得固定数量的字符。您可以做的是尝试将字符串分成行大小的块：

extension String {
  func split(width: CGFloat, font: UIFont) -> [String] {
    guard !self.isEmpty else { return [String]() }

    var lines = [String]()

    // set up range of the split
    var splitStart = self.startIndex
    var splitEnd = self.startIndex

    repeat {
      // advance the end range for the split
      splitEnd = self.index(after: splitStart)

      // initial split to test
      var line = String(characters[splitStart..<splitEnd])

      // while we're before the end test the rendered width
      while splitEnd < self.endIndex &&
        line.size(attributes: [NSFontAttributeName: font]).width < width {
          // add one more character
          splitEnd = self.index(after: splitEnd)
          line = String(characters[splitStart..<splitEnd])
      }

      // add split to array and set up next split
      lines.append(line)
      splitStart = splitEnd
    } while splitEnd < self.endIndex // don't go past the end of the string


    // add remainder of string to array
    lines.append(String(characters[splitStart..<self.endIndex]))
    return lines
  }
}

这可以通过预先计算整个字符串的宽度，除以行数，从每行的平均宽度开始，然后尝试更多或更少的字符，直到它适合。但是，这确实使代码更加复杂。

如果您想确保单词不会被拆分，那么您可以保存每个单词的开头位置，当您到达行尾时，将拆分结束放在单词之前，将单词带到下一次分裂。当然，您还需要考虑太长而无法拆分的单词、连字词等等。

另一种方法是使用NSLayoutManager 和NSTextContainer，因为您需要更高级的布局：

let text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Non est ista, inquam, Piso, magna dissensio. Minime vero istorum quidem, inquit. Graecum enim hunc versum nostis omnes-: Suavis laborum est praeteritorum memoria. Negat enim summo bono afferre incrementum diem. Quasi ego id curem, quid ille aiat aut neget. Semper enim ex eo, quod maximas partes continet latissimeque funditur, tota res appellatur. Duo Reges: constructio interrete."

let font = UIFont.systemFont(ofSize: 24.0)

// set up styled text for the container
let storage = NSTextStorage(string: text, attributes: [NSFontAttributeName: font])

// add a layout manage for the storage
let layout = NSLayoutManager()
storage.addLayoutManager(layout)

// Set up the size of the container
// width is what we care about, height is maximum
let width:CGFloat = 500
let container = NSTextContainer(size: CGSize(width: width, height: CGFloat.greatestFiniteMagnitude))

// add the container to the layout
layout.addTextContainer(container)

var lines = [String]()

// generate the layout and add each line to the array
layout.enumerateLineFragments(forGlyphRange: NSMakeRange(0, storage.length)) {
  lines.append(storage.attributedSubstring(from: $0.3).string)
}

lines.forEach { print($0) }

结果：

Lorem ipsum dolor sit amet, consectetur 
adipiscing elit. Non est ista, inquam, Piso, 
magna dissensio. Minime vero istorum 
quidem, inquit. Graecum enim hunc versum 
nostis omnes-: Suavis laborum est 
praeteritorum memoria. Negat enim summo 
bono afferre incrementum diem. Quasi ego id 
curem, quid ille aiat aut neget. Semper enim 
ex eo, quod maximas partes continet 
latissimeque funditur, tota res appellatur. Duo 
Reges: constructio interrete.

如果您愿意，您还可以通过NSLayoutManager 提供断字和其他行为。

Answer 3

我不确定这是否是最有效的方法，但我可以使用它：

func getLinesArrayOfString(forText text: String) ->NSArray {
        let font = UIFont.systemFont(ofSize: 24.0)
        let label = UILabel(frame: CGRect(x: 0, y: 0, width: self.tableView.frame.size.width, height: CGFloat.greatestFiniteMagnitude))
        label.numberOfLines = 0
        label.text = text as String
        label.font = font
        label.sizeToFit()
        var linesArray: [Any] = []


        let rect: CGRect = label.frame


        let attStr = NSMutableAttributedString(string: text)
        attStr.addAttribute((NSAttributedStringKey(rawValue: kCTFontAttributeName as String)), value: font, range: NSRange(location: 0, length: attStr.length))
        let frameSetter: CTFramesetter = CTFramesetterCreateWithAttributedString(attStr)
        let path: CGMutablePath = CGMutablePath()
        path.addRect(CGRect(x: 0, y: 0, width: rect.size.width, height: 100000), transform: .identity)
        let frame: CTFrame = CTFramesetterCreateFrame(frameSetter, CFRangeMake(0, 0), path, nil)
        let lines = CTFrameGetLines(frame) as? [Any]

        for line: Any in lines! {
            let lineRef = line
            let lineRange: CFRange = CTLineGetStringRange(lineRef as! CTLine)
            let range = NSRange(location: lineRange.location, length: lineRange.length)
            let lineString: String = (text as NSString).substring(with: range)



            CFAttributedStringSetAttribute(attStr, lineRange, kCTKernAttributeName, font)
            CFAttributedStringSetAttribute(attStr, lineRange, kCTKernAttributeName, font)
            linesArray.append(lineString)
        }
        return linesArray as NSArray
    }