A simple example to send a Notification

package com.exercise.AndroidNotification;

import java.util.Calendar;

import android.app.Activity;
import android.app.Notification;
import android.app.NotificationManager;
import android.app.PendingIntent;
import android.content.Context;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class AndroidNotification extends Activity {

private static final int MY_NOTIFICATION_ID=1;
private NotificationManager notificationManager;
private Notification myNotification;

private final String myBlog = "http://android-er.blogspot.com/";

   /** Called when the activity is first created. */
   @Override
   public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.main);
       Button buttonSend = (Button)findViewById(R.id.send);
      
       buttonSend.setOnClickListener(new Button.OnClickListener(){

  @Override
  public void onClick(View arg0) {
   // TODO Auto-generated method stub
   notificationManager =
    (NotificationManager)getSystemService(Context.NOTIFICATION_SERVICE);
   myNotification = new Notification(R.drawable.icon,
     "Notification!",
     System.currentTimeMillis());
   Context context = getApplicationContext();
   String notificationTitle = "Exercise of Notification!";
   String notificationText = "http://android-er.blogspot.com/";
   Intent myIntent = new Intent(Intent.ACTION_VIEW, Uri.parse(myBlog));
   PendingIntent pendingIntent
     = PendingIntent.getActivity(AndroidNotification.this,
       0, myIntent,
       Intent.FLAG_ACTIVITY_NEW_TASK);
   myNotification.defaults |= Notification.DEFAULT_SOUND;
   myNotification.flags |= Notification.FLAG_AUTO_CANCEL;
   myNotification.setLatestEventInfo(context,
      notificationTitle,
      notificationText,
      pendingIntent);
   notificationManager.notify(MY_NOTIFICATION_ID, myNotification);
  
  }});
   }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
   android:orientation="vertical"
   android:layout_width="fill_parent"
   android:layout_height="fill_parent"
   >
<TextView 
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="@string/hello"
   />
<Button
   android:id="@+id/send"
   android:layout_width="fill_parent"
   android:layout_height="wrap_content"
   android:text="Send a Notification"
   />
</LinearLayout>

Download the files.

Related Article:
- Start a service to send Notification

Updated:
- The Notification.Builder has been added to make it easier to construct Notifications.