How can I get treenodes statuses, I mean for the whole tree or should be item by item? It is because, the tree should keep old colapse/fold status after refresh.
you have to keep the status per item and reapply when re-building-up the tree. Example: you may store these folder-items (by their id or name...) that are opened and then be default open the new items in a closed mode - exception for the ones that you stored.
The top node of the tree is reach-able by calling FIXGRIDTreeBinding.getRootNode(). Then you can dive downwards using getChildNodes() on item level.