AlertDialogbox in Android

activity_main.xml

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

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

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    tools:context=".MainActivity" >

    <Button

        android:id="@+id/button1"

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:layout_alignParentTop="true"

        android:layout_centerHorizontal="true"

        android:layout_marginTop="107dp"

        android:text="Show Alert" />

</RelativeLayout>

ActivityMain.java

package com.karthik.alertdialog;

import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity {

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
 
  Button b = (Button)findViewById(R.id.button1);
 
  b.setOnClickListener(new OnClickListener() {
  
   @Override
   public void onClick(View v) {
    // TODO Auto-generated method stub
    AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
   
    builder.setTitle("Exit");
   
    builder.setMessage("are you sure");
   
    builder.setPositiveButton("ok", new DialogInterface.OnClickListener() {
    
     @Override
     public void onClick(DialogInterface dialog, int which) {
      // TODO Auto-generated method stub
      finish();
     }
    });
   
    builder.setNegativeButton("cancel", new DialogInterface.OnClickListener() {
    
     @Override
     public void onClick(DialogInterface dialog, int which) {
      // TODO Auto-generated method stub
     
     }
    });
   
   
    AlertDialog alert = builder.create();
   
    alert.show();
   }
  });
 }

}