Android Lab: Alert Dialog - Create Alert Dialog program

gistfile1.java

package com.example.androidlab;

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

public class MainActivity extends Activity {
  final Context context = this;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);

		Button button = (Button) findViewById(R.id.buttonAlertDialog);

		// Add button listener
		button.setOnClickListener(new OnClickListener() {
			public void onClick(View arg0) {

				AlertDialog.Builder builder = new AlertDialog.Builder(context);
				builder.setTitle("About")
						.setMessage("This is Alert Dialog!")
						.setPositiveButton("Close",
								new DialogInterface.OnClickListener() {
									public void onClick(DialogInterface dialog,
											int id) {
										dialog.cancel();
									}
								});
				;
				AlertDialog dialog = builder.create();
				dialog.show();
			}
		});
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}
}