You have two options, but first its important to point out that "leaf" is
not the same as "empty".  If you have a folder that may or may not have
children, TreeViewModel#isLeaf() should return false, meaning that the node
is not a leaf.  When the user opens thenode, one of the following can
happen.

   - You return a DataProvider with some data, in which case the children
   are rendered
   - You return a DataProvider without data, in which case the node "opens",
   but a message is displayed that the node is empty
   - You return a null NodeInfo, in which case the node is treated as a leaf

In the second option, you can still push data (such as the first child) to
the node, and it will render them.  For example, if you return an empty
ListDataProvider, then add items to the underlying list, the nodes will show
up.  If you use the other two options, you need to rerender the parent nodes
so that the Tree will call TreeViewModel#isLeaf() again.

There is no correct answer; its just a matter of user interaction.  You can
consider a folder to be a leaf, in which case it cannot be opened (no open
icon).  Or, you can consider a folder to be a non-leaf even if it is empty.
 Note that at the moment, the "no data" message is fixed, but we can
probably make that a Cell so you could add a button such as "Create New
Folder".

Thanks,
John LaBanca
[email protected]


On Thu, Nov 4, 2010 at 3:51 AM, Ståle Undheim <[email protected]> wrote:

> I am using the new GWT 2.1 CellTree to display a list of folders. From
> the UI I support adding child folders to a folder in the tree. The
> problem is, I don't know how to fire events or update the tree so that
> if I add a child to a leaf node, it's converted to a non-leaf node.
>
> Do I need to refresh the data on the parent of the node that got a
> child added?
>
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