android kotlin - EditText allow only numbers

MainActivity.kt

package com.example.jetpack

import android.os.Bundle
import android.text.InputType
import android.text.method.DigitsKeyListener
import android.widget.EditText
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*


class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        // programmatically allow only numbers
        editText2.numbersOnly()
    }
}


// extension function to allow only numbers in edit text
fun EditText.numbersOnly(){
    // numbers only soft keyboard
    inputType = InputType.TYPE_CLASS_NUMBER
    // specify the only allowed digits
    keyListener = DigitsKeyListener.getInstance("0123456789")
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/constraintLayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#FEFEFA"
    tools:context=".MainActivity">

    <!-- allow only numbers in xml -->
    <EditText
        android:id="@+id/editText"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="12dp"
        android:layout_marginEnd="12dp"
        android:padding="12dp"
        android:textSize="30sp"
        android:inputType="number"
        android:digits="0123456789"
        android:fontFamily="sans-serif-condensed-medium"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.12" />

    <EditText
        android:id="@+id/editText2"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="12dp"
        android:layout_marginTop="24dp"
        android:layout_marginEnd="12dp"
        android:padding="12dp"
        android:textSize="30sp"
        android:fontFamily="sans-serif-condensed-medium"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/editText" />

</androidx.constraintlayout.widget.ConstraintLayout>