Alert dialog

I have been trying to show a alert dialog for one of my projects, so here is how you do it...

package <your package name>;

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

public class Registration extends Activity {
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.registration);//this is the XML file that you will using for your layout

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

        button.setOnClickListener(clicklistener);

       
       
    }
    public OnClickListener clicklistener = new OnClickListener() {
        public void onClick(View v) {
          // do something when the button is clicked
            AlertDialog.Builder builder = new AlertDialog.Builder(v.getContext());
            builder.setMessage("Are you sure you want to exit?")
                   .setCancelable(false)
                   .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                       public void onClick(DialogInterface dialog, int id) {
                                                   }
                   })
                   .setNegativeButton("No", new DialogInterface.OnClickListener() {
                       public void onClick(DialogInterface dialog, int id) {
                                               }
                   });
            builder.create();
            builder.show();
        }
    };

   
}