Swift UILabel linespacing for single line text-CodePudding

I want to increase padding inside UILabel cell (top and bottom),with modifying line height priority. Currently i use that extension:

func setLineSpacing(lineSpacing: CGFloat = 0.0, lineHeightMultiple: CGFloat = 0.0) {

          guard let labelText = self.text else { return }

          let paragraphStyle = NSMutableParagraphStyle()
          paragraphStyle.lineSpacing = lineSpacing
          paragraphStyle.lineHeightMultiple = lineHeightMultiple

          let attributedString: NSMutableAttributedString
          if let labelattributedText = self.attributedText {
              attributedString = NSMutableAttributedString(attributedString: labelattributedText)
          } else {
              attributedString = NSMutableAttributedString(string: labelText)
          }

          // (Swift 4.2 and above) Line spacing attribute
          attributedString.addAttribute(NSAttributedString.Key.paragraphStyle, value: paragraphStyle, range:NSMakeRange(0, attributedString.length))
    
          print("attributed string \(attributedString)")
          self.attributedText = attributedString
      }

My problem is, it doesn't modify vertical gaps when number of lines of UILabel is single. Therefore i failed to achieve specific offsets corresponding to UI design when there is specific line height for label is set.

CodePudding user response：

The paragraphStyle is interested lines in Label not the whole component. You are setting some properties between this lines(cells) . So when number of lines is 1 , There is nothing to affect.If you want to give top and bottom between text(not cells) and UILabel component, you must give top and bottom space to Label .

Example Class

class labelClass : UILabel{

var padding = UIEdgeInsets()

required init?(coder: NSCoder) {
    super.init(coder: coder)
}

func setLineSpacing(lineSpacing: CGFloat = 0.0, lineHeightMultiple: CGFloat = 0.0) {
    padding = UIEdgeInsets(top: lineSpacing, left: 0, bottom: lineSpacing, right: 0)
          guard let labelText = self.text else { return }

          let paragraphStyle = NSMutableParagraphStyle()
    
          paragraphStyle.lineSpacing = lineSpacing
          paragraphStyle.lineHeightMultiple = lineHeightMultiple
          let attributedString: NSMutableAttributedString
          if let labelattributedText = self.attributedText {
              attributedString = NSMutableAttributedString(attributedString: labelattributedText)
          } else {
              attributedString = NSMutableAttributedString(string: labelText)
          }

          // (Swift 4.2 and above) Line spacing attribute
          attributedString.addAttribute(NSAttributedString.Key.paragraphStyle, value: paragraphStyle, range:NSMakeRange(0, attributedString.length))
    
    
          print("attributed string \(attributedString)")
    
          self.attributedText = attributedString
    
 

      }

override func drawText(in rect: CGRect) {
    super.drawText(in: rect.inset(by: padding))
}

override var intrinsicContentSize : CGSize {
    let superContentSize = super.intrinsicContentSize
    let width = superContentSize.width   padding.left   padding.right
    let heigth = superContentSize.height   padding.top   padding.bottom
    return CGSize(width: width, height: heigth)
}

}

According to Comment:

You can get current text numberOfLines count by using link

extension UILabel {
func calculateMaxLines() -> Int {
    let maxSize = CGSize(width: frame.size.width, height: CGFloat(Float.infinity))
    let charSize = font.lineHeight
    let text = (self.text ?? "") as NSString
    let textSize = text.boundingRect(with: maxSize, options: .usesLineFragmentOrigin, attributes: [NSAttributedString.Key.font: font], context: nil)
    let linesRoundedUp = Int(ceil(textSize.height/charSize))
    return linesRoundedUp
}
}

And do operation when numberOfLines is 1

 func setLineSpacing(lineSpacing: CGFloat = 0.0, lineHeightMultiple: CGFloat = 0.0) {
    padding = UIEdgeInsets(top: 0, left: 0, bottom: 0, right: 0) // CHANGED

    guard let labelText = self.text else { return }
    
    let paragraphStyle = NSMutableParagraphStyle()
    
    paragraphStyle.lineSpacing = lineSpacing
    paragraphStyle.lineHeightMultiple = lineHeightMultiple
    let attributedString: NSMutableAttributedString
    if let labelattributedText = self.attributedText {
        attributedString = NSMutableAttributedString(attributedString: labelattributedText)
    } else {
        attributedString = NSMutableAttributedString(string: labelText)
    }
    
    // (Swift 4.2 and above) Line spacing attribute
    attributedString.addAttribute(NSAttributedString.Key.paragraphStyle, value: paragraphStyle, range:NSMakeRange(0, attributedString.length))
    
    
    
    self.attributedText = attributedString
    if self.calculateMaxLines() == 1 { // CHANGED
        padding = UIEdgeInsets(top: lineSpacing, left: 0, bottom: lineSpacing, right: 0)

    }
    
    
}