creating notification

First we need to use Notification builder

NotificationCompat.Builder mBuilder =
    new NotificationCompat.Builder(this)
    .setSmallIcon(R.drawable.notification_icon)
    .setContentTitle("My notification")
    .setContentText("Hello World!");

Then we need to have a intent

Intent resultIntent = new Intent(this, ResultActivity.class);

need not to say that if it is being defined in a inner class then instead of writing this we write MainActivitiy.this

Now, we create a pending  activity

PendingIntent resultPendingIntent =
    PendingIntent.getActivity(
    this,
    0,
    resultIntent,
    PendingIntent.FLAG_UPDATE_CURRENT);

WE make our builder content intent equal to our pending activity

mBuilder.setContentIntent(resultPendingIntent);

Now the last thing i.e. to issue the notification , which is done with the help of notification manager, which get the android notification service

int mNotificationId = 001;
// Gets an instance of the NotificationManager service
NotificationManager mNotifyMgr = 
        (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
// Builds the notification and issues it.
mNotifyMgr.notify(mNotificationId, mBuilder.build());