Cursor goes to end after setting text to UITextField inside shouldChangeCharactersIn

问题

I have text label which has phone number in it. I mask the phone number when user is typing so that in shouldChangeCharactersIn function;

I get user input (string)
Add that input to text which is already written in UITextField
Mask text and set it to UITextField
Return false

My question is that after I set text of UITextfield (delete or add new character UITextField, cursor moves to the end but I want it to stay in the same position. (By meaning same position, I mean same when I don't implement shouldChangeCharactersIn function) How can I do that? Thank you.

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    guard CharacterSet(charactersIn: "0123456789").isSuperset(of: CharacterSet(charactersIn: string)) else {
        return false
    }
    if let text = textField.text {
        let newLength = text.count + string.count - range.length
        let newText = text + string

        let textFieldText: NSString = (textField.text ?? "") as NSString
        let txtAfterUpdate = textFieldText.replacingCharacters(in: range, with: string)
            if(newLength <= 15){
                //textField.text = txtAfterUpdate
                textField.text = txtAfterUpdate.digits.applyPatternOnNumbers()
                return false
            }
            return newLength <= 15
    }
    return true
}

Mask Function:

func applyPatternOnNumbers(pattern: String = "(###) ### ## ##", replacmentCharacter: Character = "#") -> String {
var pureNumber = self.replacingOccurrences( of: "[^0-9]", with: "", options: .regularExpression)
for index in 0 ..< pattern.count {
    guard index < pureNumber.count else { return pureNumber }
    let stringIndex = String.Index(encodedOffset: index)
    let patternCharacter = pattern[stringIndex]
    guard patternCharacter != replacmentCharacter else { continue }
    pureNumber.insert(patternCharacter, at: stringIndex)
}
return pureNumber
}

What I want in GIF

回答1:

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

        guard CharacterSet(charactersIn: "0123456789").isSuperset(of: CharacterSet(charactersIn: string)) else {
            return false
        }
        if let text = textField.text {
            let newLength = text.count + string.count - range.length
            let newText = text + string

            let textFieldText: NSString = (textField.text ?? "") as NSString
            let txtAfterUpdate = textFieldText.replacingCharacters(in: range, with: string)
            if(newLength <= 15){

                var currentPosition = 0
                if let selectedRange = textField.selectedTextRange {
                    currentPosition = textField.offset(from: textField.beginningOfDocument, to: selectedRange.start)
                }

                if(string == ""){
                    if(currentPosition == 2){
                        if(textField.text!.count > 2){
                            currentPosition = 1
                        }else{
                            currentPosition = 0
                        }
                    }else if(currentPosition == 7){
                        currentPosition = 4
                    }else if(currentPosition == 11){
                        currentPosition = 9
                    }else if(currentPosition == 14){
                        currentPosition = 12
                    }else{
                        if(currentPosition != 1){
                            currentPosition = currentPosition - 1
                        }
                    }
                }else{
                    if(currentPosition == 0){
                        currentPosition = 2
                    }else if(currentPosition == 4){
                        currentPosition = 7
                    }else if(currentPosition == 9){
                        currentPosition = 11
                    }else if(currentPosition == 12){
                        currentPosition = 14
                    }else{
                        currentPosition = currentPosition + 1
                    }
                }

                textField.text = txtAfterUpdate.applyPatternOnNumbers()
                print("textField Length -> : \(textField.text?.count ?? 0)")

                    if let newPosition = textField.position(from: textField.beginningOfDocument, offset: currentPosition) {
                        textField.selectedTextRange = textField.textRange(from: newPosition, to: newPosition)
                    }

                return false
            }
            return newLength <= 15
        }
        return true
    }

来源：https://stackoverflow.com/questions/51784571/cursor-goes-to-end-after-setting-text-to-uitextfield-inside-shouldchangecharacte

标签

ios

swift

uitextfield