[Zope] Problems of using Navigator products

[cfkwok_hknet]

Hi,

I am trying to use the Navigator product in a Zope server.
I use the navigator_demo/simple_demo as a starting point. However,
when I add a NavItem under the navbar, it seems that renderItem can
not detect the new added items and nothing changed in the navigator bar.

What is the right procedure to add a NavItem?
Thanks!

C.F.Kwok