Alert Dialog Tutorial in Android

Alert Dialog :

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Alert Dialog is used to display a pop up or dialog in the Activity. It is generally used to ask question from a user with the help of popup dialog at certain event.

Creating an Alert Dialog is very easy in Android with the use of AlertDialog class.

Create a new project in Eclipse : File => New => Android Application Project and give a package name as com.javalanguageprogramming.alertdialogdemo.

Copy the code of activity_main.xml file as shown below :

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"  
   xmlns:tools="http://schemas.android.com/tools"  
   android:layout_width="fill_parent"  
   android:layout_height="fill_parent"  
   >  
   
   <Button  
     android:id="@+id/alertButton"  
     android:layout_width="200dp"  
     android:layout_height="wrap_content"  
     android:text="Get Alert Dialog"   
     android:layout_gravity="center"  
     android:layout_marginLeft="50dp"  
     />  
   
 </LinearLayout>  
   

In this file we are creating a button which show a dialog when clicked and ask from user that you want to exit from application or not.

Copy the code of MainActivity.java as shown below :

 package com.javalanguageprogramming.alertdialogdemo;  
   
 import android.app.Activity;  
 import android.app.AlertDialog;  
 import android.app.AlertDialog.Builder;  
 import android.content.DialogInterface;  
 import android.content.DialogInterface.OnClickListener;  
 import android.os.Bundle;  
 import android.view.View;  
 import android.widget.Button;  
 import android.widget.Toast;  
   
   
 public class MainActivity extends Activity {  
   
      Button alertButton;  
      Builder dialog;  
   
      @Override  
      protected void onCreate(Bundle savedInstanceState) {  
           super.onCreate(savedInstanceState);  
           setContentView(R.layout.activity_main);  
   
           // initialize button variable  
           alertButton = (Button) findViewById(R.id.alertButton);  
   
           // initialize alert dialog  
           dialog = new AlertDialog.Builder(MainActivity.this);  
             
           //if button is clicked than set the alert dialog.  
           alertButton.setOnClickListener(new View.OnClickListener() {  
                  
                @Override  
                public void onClick(View v) {  
                     // call the alertDialogSetup method when button is clicked  
                     alertDialogSetup();  
                       
                }  
           });  
   
      }  
   
      private void alertDialogSetup() {  
           // set a title  
           dialog.setTitle("Exit Application");  
   
           // set a message  
           dialog.setMessage("Are you sure?");  
   
           // set positive button with OnClickListener for positive response  
           dialog.setPositiveButton("Yes", new OnClickListener() {  
   
                @Override  
                public void onClick(DialogInterface dialog, int which) {  
                     // Exit application when user click on yes  
                     System.exit(0);  
   
                }  
           });  
             
           // set negative button with OnClickListener for negative response  
           dialog.setNegativeButton("NO", new OnClickListener() {  
                  
                @Override  
                public void onClick(DialogInterface dialog, int which) {  
                     //cancel the dialog on negative button with the use of DialogInterface reference  
                     dialog.cancel();  
                       
                }  
           });  
             
           //there is one more button in alert dialog in the center called neutral button  
           dialog.setNeutralButton("Neutral", new OnClickListener() {  
                  
                @Override  
                public void onClick(DialogInterface dialog, int which) {  
                     // make a toast that neutral button is clicked  
                     Toast.makeText(MainActivity.this, "Neutral button is clicked", Toast.LENGTH_LONG).show();  
                       
                }  
           });  
             
           //you can use image with the text in the dialog  
           dialog.setIcon(R.drawable.ic_launcher);  
             
           // Now show the dialog on the activity  
           dialog.show();  
      }  
 }  
   

In this Activity, we are creating three buttons (Positive => Yes, Negative => No, Neutral => Cancel) in the dialog. You can create single button or two buttons dialog.