Android RatingBar in AlertDialog Popup

package com.myapp;

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

public class MainActivity extends Activity {

	public TextView txtView;
	
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
        
  
		txtView = (TextView)findViewById(R.id.textView1); // TextView
		
        // Button1
        final Button btn1 = (Button) findViewById(R.id.button1);
        btn1.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
            	ShowDialog();
            }	
        });
        
	}
	
	public void ShowDialog()
	{
		final AlertDialog.Builder popDialog = new AlertDialog.Builder(this);
		final RatingBar rating = new RatingBar(this);
		rating.setMax(6);

		popDialog.setIcon(android.R.drawable.btn_star_big_on);
		popDialog.setTitle("Vote!! ");
		popDialog.setView(rating);

		// Button OK
		popDialog.setPositiveButton(android.R.string.ok,
				new DialogInterface.OnClickListener() {
					public void onClick(DialogInterface dialog, int which) {
						txtView.setText(String.valueOf(rating.getProgress()));
						dialog.dismiss();
					}

				})

		// Button Cancel
				.setNegativeButton("Cancel",
						new DialogInterface.OnClickListener() {
							public void onClick(DialogInterface dialog, int id) {
								dialog.cancel();
							}
						});

		popDialog.create();
		popDialog.show();
        
	}
	
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.activity_main, menu);
        return true;
    }

}