Progress Notification in Android Example

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
 
    <Button
        android:id="@+id/button1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="20dp"
        android:text="Start Download" />
 
</LinearLayout>

import android.app.Activity;
import android.app.NotificationManager;
import android.content.Context;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v4.app.NotificationCompat;
import android.support.v4.app.NotificationCompat.Builder;
import android.util.Log;
import android.view.View;
import android.widget.Button;
 
public class MainActivity extends Activity {
    private NotificationManager mNotifyManager;
    private Builder mBuilder;
    int id = 1;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        Button b1 = (Button) findViewById(R.id.button1);
        b1.setOnClickListener(new View.OnClickListener() {
 
            public void onClick(View arg0) {
                mNotifyManager = (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
                mBuilder = new NotificationCompat.Builder(MainActivity.this);
                mBuilder.setContentTitle("Download")
                        .setContentText("Download in progress")
                        .setSmallIcon(R.drawable.ic_download);
 
                new Downloader().execute();
            }
        });
    }
 
    private class Downloader extends AsyncTask<Void, Integer, Integer> {
 
        @Override
        protected void onPreExecute() {
            super.onPreExecute();
 
            // Displays the progress bar for the first time.
            mBuilder.setProgress(100, 0, false);
            mNotifyManager.notify(id, mBuilder.build());
        }
 
        @Override
        protected void onProgressUpdate(Integer... values) {
            // Update progress
            mBuilder.setProgress(100, values[0], false);
            mNotifyManager.notify(id, mBuilder.build());
            super.onProgressUpdate(values);
        }
 
        @Override
        protected Integer doInBackground(Void... params) {
            int i;
            for (i = 0; i <= 100; i += 5) {
                // Sets the progress indicator completion percentage
                publishProgress(Math.min(i, 100));
                try {
                    // Sleep for 5 seconds
                    Thread.sleep(2 * 1000);
                } catch (InterruptedException e) {
                    Log.d("TAG", "sleep failure");
                }
            }
            return null;
        }
 
        @Override
        protected void onPostExecute(Integer result) {
            super.onPostExecute(result);
            mBuilder.setContentText("Download complete");
            // Removes the progress bar
            mBuilder.setProgress(0, 0, false);
            mNotifyManager.notify(id, mBuilder.build());
        }
    }
}