/**
   * Returns the <tt>NotificationService</tt> obtained from the bundle context.
   *
   * @return The <tt>NotificationService</tt> obtained from the bundle context.
   */
  public static NotificationService getNotificationService() {
    if (notificationService == null) {
      // Get the notification service implementation
      ServiceReference notifReference =
          bundleContext.getServiceReference(NotificationService.class.getName());

      notificationService = (NotificationService) bundleContext.getService(notifReference);

      if (notificationService != null) {
        // Register a popup message for a device configuration changed
        // notification.
        notificationService.registerDefaultNotificationForEvent(
            DEVICE_CONFIGURATION_HAS_CHANGED,
            net.java.sip.communicator.service.notification.NotificationAction.ACTION_POPUP_MESSAGE,
            "Device onfiguration has changed",
            null);
      }
    }

    return notificationService;
  }