MMDDYYYYEditText.kt

import android.content.Context
import android.text.Editable
import android.text.InputFilter
import android.text.InputType
import android.text.TextWatcher
import android.util.AttributeSet
import android.widget.EditText
import androidx.appcompat.widget.AppCompatEditText
import java.text.SimpleDateFormat
import java.util.*

class MMDDYYYYEditText @JvmOverloads constructor(
    context: Context,
    attrs: AttributeSet? = null,
    defStyleAttr: Int = androidx.appcompat.R.attr.editTextStyle
) : AppCompatEditText(context, attrs, defStyleAttr) {

    var onDateFilled: ((Date) -> Unit)? = null

    init {
        MMDDYYYYInputHelper(this) {
            onDateFilled?.invoke(it)
        }
    }

    override fun onSelectionChanged(selStart: Int, selEnd: Int) {
        val len = text?.length ?: 0
        setSelection(len)
        super.onSelectionChanged(len, len)
    }

    internal class MMDDYYYYInputHelper(
        private val editText: EditText,
        private val onDateFilled: (Date) -> Unit
    ) :
        TextWatcher {

        companion object {
            private const val HINT = "MM/DD/YYYY"
            private val dateFormat = SimpleDateFormat("MM/dd/yyyy", Locale.ENGLISH)
        }

        private var changeHandled = false

        init {
            editText.hint = HINT
            editText.inputType = InputType.TYPE_CLASS_NUMBER
            editText.addTextChangedListener(this)
            editText.filters = arrayOf(InputFilter.LengthFilter(HINT.length))
        }

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

        override fun onTextChanged(s: CharSequence, start: Int, before: Int, count: Int) {
            var value = s.toString()
            if (changeHandled) {
                changeHandled = false
                return
            }
            changeHandled = true
            if (value.length >= 2) {
                val month = value.substring(0, 2).toInt()
                if (month > 12 || month == 0) {
                    value = "12"
                }
            }
            value = addDivider(value, 2, start, before)

            if (value.length >= 5) {
                var day = value.substring(3, 5).toInt()
                if (day > 31 || day == 0) {
                    value = value.replace(day.toString(), "31")
                    day = 31
                }
                val month = value.substring(0, 2).toInt()
                if (day == 31 && (month == 4 || month == 6 || month == 9 || month == 11)) {
                    value = value.replace(day.toString(), "30")
                } else if (month == 2 && day == 31) {
                    value = value.replace(day.toString(), "29")
                }
            }
            value = addDivider(value, 5, start, before)

            editText.setText(value)
            editText.setSelection(editText.text?.length ?: 0)

        }

        override fun afterTextChanged(s: Editable) {
            if (s.length == HINT.length) {
                try {
                    dateFormat.parse(s.toString())?.let { onDateFilled.invoke(it) }
                } catch (t: Throwable) {
                }
            }
        }

        private fun addDivider(working: String, position: Int, start: Int, before: Int): String {
            if (working.length == position) {
                return if (before <= position && start < position)
                    "$working/"
                else
                    working.dropLast(1)
            }
            return working
        }
    }
}