Back Button Coding Demo

Demo:

1) MainActivity.java: 

package com.venky.backbuttondemo;

import android.app.Activity;

import android.app.AlertDialog;

import android.content.DialogInterface;

import android.os.Bundle;

public class MainActivity extends Activity {

       @Override

       protected void onCreate(Bundle savedInstanceState) {

             super.onCreate(savedInstanceState);

             setContentView(R.layout.activity_main);

       }

       @Override

       public void onBackPressed() {

             displayDialog();

       }

       public void displayDialog() {

             AlertDialog.Builder alert = new AlertDialog.Builder(MainActivity.this);

             alert.setMessage("Are you sure to leave this App");

             alert.setNegativeButton("Cancel",

                           new DialogInterface.OnClickListener() {

                                 @Override

                                 public void onClick(DialogInterface dialog, int pos) {

                                        dialog.cancel();

                                 }

                           });

             alert.setPositiveButton("OK", new DialogInterface.OnClickListener() {

                    @Override

                    public void onClick(DialogInterface dialog, int pos) {

                           finish();

                    }

             });

             alert.show();

       }

}

2) activity_main.xml: 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:id="@+id/LinearLayout1"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:background="#5F04B4"

    android:orientation="vertical" >

    <TextView

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:layout_marginTop="50dp"

        android:gravity="center"

        android:text="Back Button Behavior Chenged"

        android:textColor="#ffffff"

        android:textSize="18dp"

        android:textStyle="bold" />

</LinearLayout>

3) Download this Project Click Here