Android AlertDialog Popup

package com.myapp;

import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.app.Activity;
import android.app.AlertDialog;

public class MainActivity extends Activity {

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
        
		final AlertDialog.Builder adb = new AlertDialog.Builder(this);
		
        // Button1
        final Button btn1 = (Button) findViewById(R.id.button1);
        btn1.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
            	
            	AlertDialog ad = adb.create();
            	ad.setMessage("Hi Hi");
            	ad.show();
            	
            }	
        });
        
	}
	
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

}

package com.myapp;

import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.app.Activity;
import android.app.AlertDialog;

public class MainActivity extends Activity {

	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
        
        final AlertDialog.Builder dDialog = new AlertDialog.Builder(this);
		
        // Button1
        final Button btn1 = (Button) findViewById(R.id.button1);
        btn1.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
            	
            	dDialog.setTitle("Oh!! Android ");
            	dDialog.setIcon(android.R.drawable.btn_star_big_on); 
            	dDialog.setMessage("Sawatdee Android!");
				dDialog.setPositiveButton("Close", null);
            	dDialog.show();
            	
            }	
        });
        
	}
	
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

}