[Zope-CMF] Why my CMF Type can't list in the folder content?

[???]

hi,

It is my first time writing a custom Type in CMF. It is a ZClass based type.
It nearly works well.

I can add, edit, search it. But it doesn't show in the Plone's folder
contents. And I found it could list in the ZMI.

I checked the PloneFolder Type Infomation. It doesn't filter anything.

Who can help me? What is wrong?

panjunyong