android kotlin - On back button pressed example

MainActivity.kt


package com.example.jetpack

import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AlertDialog
import androidx.appcompat.app.AppCompatActivity


class MainActivity : AppCompatActivity() {

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


    // called when the activity has detected the user's press of the back key.
    // the default implementation simply finishes the current activity,
    // but you can override this to do whatever you want.
    override fun onBackPressed() {
        AlertDialog.Builder(this).apply {
            setTitle("Please confirm.")
            setMessage("Are you want to exit the app?")

            setPositiveButton("Yes") { _, _ ->
                // if user press yes, then finish the current activity
                super.onBackPressed()
            }

            setNegativeButton("No"){_, _ ->
                // if user press no, then return the activity
                Toast.makeText(this@MainActivity, "Thank you",
                    Toast.LENGTH_LONG).show()
            }

            setCancelable(true)
        }.create().show()
    }
}

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="#EDEAE0"
    tools:context=".MainActivity"/>