Monday, 1 July 2013

Display Alert on Back button Pressed in Android Studio

Description: When user wants to exit from application, he is prompted to exit from application.
Complexity Level: Beginner
Keywords: back, back button, android, android studio, alert, dialog, onbackpress

                Alert means to get user’s input when needed. Most of us played games and when we try to exit it by pressing “Back” button in Android phone, it ask for “Do you really want to exit?”.             So, in this article we are going to learn how to prevent user to exit from application without giving response.

Step 1:
Create a new Project with following parameters.

Step 2:
Open your Main Activity file, in my case it is “BackPressActivity” and paste following code inside.
package com.example.alertonbackpressdemo;

import android.content.DialogInterface;
import android.os.Bundle;
import android.view.Menu;

public class BackPressActivity extends Activity {
    protected void onCreate(Bundle savedInstanceState) {

    public void onBackPressed() {
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setMessage("Do you want to Exit?");
        builder.setPositiveButton("Yes", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                //if user pressed "yes", then he is allowed to exit from application
        builder.setNegativeButton("No",new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                //if user select "No", just cancel this dialog and continue with app
        AlertDialog alert=builder.create();;

Let’s understand Alert Dialog and its different methods.
In code there is written “builder.setCancelable(false);” which means that user can’t cancel this dialog by pressing back again or touch outside the alert dialog box and dismiss it. So user has to press one of the options you have provided to him.
Next is “builder.setMessage("Do you want to Exit?");”. Here you can write your own message which will be displayed to user in alert.
builder.setPositiveButton” will set a positive button in left side. Parameter will accept the name of that button as you can see in code is “Yes”. Same thing is set for “builder.setNegativeButton”. When you set these buttons, you need to pass a listener which will be fired when user click one of the button.
Step 3:
Run your application.

                In this article, we learned “How to show Alert Dialog” and “Show dialog at BACK button pressed”.

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