How to mask an EditText to show the dd/mm/yyyy date format

Question

How can I format an EditText to follow the \"dd/mm/yyyy\" format the same way that we can format using a TextWatcher to mask

Answer 1

Juan Cortés' wiki works like a charm https://stackoverflow.com/a/16889503/3480740

Here my Kotlin version

fun setBirthdayEditText() {

    birthdayEditText.addTextChangedListener(object : TextWatcher {

        private var current = ""
        private val ddmmyyyy = "DDMMYYYY"
        private val cal = Calendar.getInstance()

        override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
            if (p0.toString() != current) {
                var clean = p0.toString().replace("[^\\d.]|\\.".toRegex(), "")
                val cleanC = current.replace("[^\\d.]|\\.", "")

                val cl = clean.length
                var sel = cl
                var i = 2
                while (i <= cl && i < 6) {
                    sel++
                    i += 2
                }
                //Fix for pressing delete next to a forward slash
                if (clean == cleanC) sel--

                if (clean.length < 8) {
                    clean = clean + ddmmyyyy.substring(clean.length)
                } else {
                    //This part makes sure that when we finish entering numbers
                    //the date is correct, fixing it otherwise
                    var day = Integer.parseInt(clean.substring(0, 2))
                    var mon = Integer.parseInt(clean.substring(2, 4))
                    var year = Integer.parseInt(clean.substring(4, 8))

                    mon = if (mon < 1) 1 else if (mon > 12) 12 else mon
                    cal.set(Calendar.MONTH, mon - 1)
                    year = if (year < 1900) 1900 else if (year > 2100) 2100 else year
                    cal.set(Calendar.YEAR, year)
                    // ^ first set year for the line below to work correctly
                    //with leap years - otherwise, date e.g. 29/02/2012
                    //would be automatically corrected to 28/02/2012

                    day = if (day > cal.getActualMaximum(Calendar.DATE)) cal.getActualMaximum(Calendar.DATE) else day
                    clean = String.format("%02d%02d%02d", day, mon, year)
                }

                clean = String.format("%s/%s/%s", clean.substring(0, 2),
                        clean.substring(2, 4),
                        clean.substring(4, 8))

                sel = if (sel < 0) 0 else sel
                current = clean
                birthdayEditText.setText(current)
                birthdayEditText.setSelection(if (sel < current.count()) sel else current.count())
            }
        }

        override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
        }

        override fun afterTextChanged(p0: Editable) {

        }
    })
}