Swift : tap on a part of text of UILabel

Question

I have a problem that \"boundingRectForGlyphRange\" always returns CGRect.zero \"0.0, 0.0, 0.0, 0.0\". \"boundingRectForGlyphRange\" is not working. For example, I am coding

Answer 1

For multi-line labels you have to set the textStorage font or the incorrect range will be returned

guard let attributedString = self.attributedText else { return }

let mutableAttribString = NSMutableAttributedString(attributedString: attributedString)
mutableAttribString.addAttributes([NSAttributedString.Key.font: myFont], range: NSRange(location: 0, length: attributedString.length))

let textStorage = NSTextStorage(attributedString: mutableAttribString)

There are a lot of answers to this question. However, there are many people complaining that the tap fails for multi-line labels and that is correct for most answers on this page. The incorrect range for the tap is returned because the textStorage doesn't have the correct font.

let textStorage = NSTextStorage(attributedString: label.attributedText!)

You can fix this quickly by adding the correct font to your textStorage instance:

guard let attributedString = self.attributedText else { return -1 }

let mutableAttribString = NSMutableAttributedString(attributedString: attributedString)
mutableAttribString.addAttributes([NSAttributedString.Key.font: myFont], range: NSRange(location: 0, length: attributedString.length))

let textStorage = NSTextStorage(attributedString: mutableAttribString)

Putting it all together you get something like this:

protocol AtMentionsLabelTapDelegate: class {
  func labelWasTappedForUsername(_ username: String)
}

class AtMentionsLabel: UILabel {
  private var tapGesture: UITapGestureRecognizer = UITapGestureRecognizer()
  weak var tapDelegate: AtMentionsLabelTapDelegate?

  var mentions: [String] = [] // usernames to style

  override init(frame: CGRect) {
    super.init(frame: frame)
    commonInit()
  }

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

  func commonInit() {
    isUserInteractionEnabled = true

    lineBreakMode = .byWordWrapping
    tapGesture = UITapGestureRecognizer()
    tapGesture.addTarget(self, action: #selector(handleLabelTap(recognizer:)))
    tapGesture.numberOfTapsRequired = 1
    tapGesture.isEnabled = true
    addGestureRecognizer(tapGesture)
  }


  @objc func handleLabelTap(recognizer: UITapGestureRecognizer) {
    let tapLocation = recognizer.location(in: self)
    let tapIndex = indexOfAttributedTextCharacterAtPoint(point: tapLocation)

    for username in mentions {
      if let ranges = self.attributedText?.rangesOf(subString: username) {
        for range in ranges {
          if tapIndex > range.location && tapIndex < range.location + range.length {
            tapDelegate?.labelWasTappedForUsername(username)
            return
          }
        }
      }
    }
  }

  func indexOfAttributedTextCharacterAtPoint(point: CGPoint) -> Int {
    guard let attributedString = self.attributedText else { return -1 }

    let mutableAttribString = NSMutableAttributedString(attributedString: attributedString)
    // Add font so the correct range is returned for multi-line labels
    mutableAttribString.addAttributes([NSAttributedString.Key.font: font], range: NSRange(location: 0, length: attributedString.length))

    let textStorage = NSTextStorage(attributedString: mutableAttribString)

    let layoutManager = NSLayoutManager()
    textStorage.addLayoutManager(layoutManager)

    let textContainer = NSTextContainer(size: frame.size)
    textContainer.lineFragmentPadding = 0
    textContainer.maximumNumberOfLines = numberOfLines
    textContainer.lineBreakMode = lineBreakMode
    layoutManager.addTextContainer(textContainer)

    let index = layoutManager.characterIndex(for: point, in: textContainer, fractionOfDistanceBetweenInsertionPoints: nil)
    return index
  }
}

extension NSAttributedString {
  func rangesOf(subString: String) -> [NSRange] {
    var nsRanges: [NSRange] = []
    let ranges = string.ranges(of: subString, options: .caseInsensitive, locale: nil)

    for range in ranges {
      nsRanges.append(range.nsRange)
    }

    return nsRanges
  }
}

extension String {
  func ranges(of substring: String, options: CompareOptions = [], locale: Locale? = nil) -> [Range] {
    var ranges: [Range] = []
    while let range = self.range(of: substring, options: options, range: (ranges.last?.upperBound ?? self.startIndex) ..< self.endIndex, locale: locale) {
      ranges.append(range)
    }
    return ranges
  }
}