Android EditText TextWatcher for formatting credit card number made with Kotlin

CreditCardNumberFormattingTextWatcher.kt

class CreditCardNumberFormattingTextWatcher : TextWatcher {
    private var current = ""

    override fun onTextChanged(s: CharSequence, start: Int, before: Int, count: Int) {
    }

    override fun beforeTextChanged(s: CharSequence, start: Int, count: Int, after: Int) {
    }

    override fun afterTextChanged(s: Editable) {
        if (s.toString() != current) {
            val userInput = s.toString().replace(nonDigits,"")
            if (userInput.length <= 16) {
                current = userInput.chunked(4).joinToString(" ")
                s.filters = arrayOfNulls<InputFilter>(0)
            }
            s.replace(0, s.length, current, 0, current.length)
        }
    }

    companion object {
        private val nonDigits = Regex("[^\\d]")
    }
}

Worked like charm. Thanks

Thanks

You can refactor this part of the code

val userInput = s.toString().replace("[^\\d]".toRegex(), "")
            if (userInput.length <= 16) {
                val sb = StringBuilder()
                for (i in 0..userInput.length - 1) {
                    if (i % 4 == 0 && i > 0) {
                        sb.append(" ")
                    }
                    sb.append(userInput[i])
                }
                current = sb.toString()

using something like

current = userInput.replace(" ","").chunk(2).jointString(" ")

And a question

Why is needed this line? If I remove it, the format doesn't work

s.filters = arrayOfNulls(0)

@Mun0n Thanks for the suggestion, that simplified it quite a bit. I honestly don't remember why the filters need to be set, nor why emptyArray wouldn't be sufficient. 🤷‍♂️

@Mun0n Thanks for the suggestion, that simplified it quite a bit. I honestly don't remember why the filters need to be set, nor why emptyArray wouldn't be sufficient. 🤷‍♂️

this line is needed if you set inputType as a number for edit text in xml file. cause number input type is not accept space.

how this code does't go into infinite loop? i think the answer is in s.filters = arrayOfNulls<InputFilter>(0) but i cannot figure out

how this code does't go into infinite loop? i think the answer is in s.filters = arrayOfNulls<InputFilter>(0) but i cannot figure out

if (s.toString() != current) will prevent that.

Work like charm, Thanks man!

You saved my day, Thanks man!

@mohsenmdb Cheers, my pleasure!