Re: CellTree, adding data to a child node and refresh

You are correct that refreshing the ListDataProvider<ObjectA> will only update that level of the tree.  You need to keep a reference to ListDataProvider<ObjectB> in order to refresh that section of the tree.  That probably means creating a parallel tree structure of ListDataProviders, or at least having a map for ObjectA to the ListDataProvider<ObjectB> that represents its children.

One workaround is to close/reopen the TreeNode, which will cause it to request a new DefaultNodeInfo from the TreeViewModel.

Thanks,
John LaBanca
jlabanca@google.com

On Wed, Nov 3, 2010 at 1:13 PM, Ümit <uemit.seren@gmail.com> wrote:

Hi all,

I have an issue with the CellTree and adding new items to a child
node. I am not exactly sure if my approach is flawed or maybe there is
an issue with the CellTree but maybe somebody can help with that
problem.
So basically I followed the CellTree example from the showace.

I have a CellTree which consists of 3 nodes which correspond to three
different DTO's (let's say: ObjectA, ObjectB and ObjectC)
Each ObjectA instance contains a list of ObjectBs and each ObjectB has
a list of ObjectCs.

ObjectA should be displayed in the root node, ObejctB in the second
node and ObjectC in the third node (= leaf node).

I created a CustomTreeModel with a custom constructor which takes a
List of ObjectA instances as a parameter. In the constructor I create
a ListDataProvider which is stored as a member variable in the
CustomTreeModel.

Then I define the necessary Cells for each node level and implement
the  public <T> NodeInfo<?> getNodeInfo(T value)  function.

This looks something like this:
public <T> NodeInfo<?> getNodeInfo(T value) {
               if (value == null)
               {
                       return new DefaultNodeInfo<ObjectA>
                               (listDataProvider,new TextCell());
               }
               else if (value instanceof ObjectA)
               {
                       ObjectA object  = (ObjectA)value;
                       return new DefaultNodeInfo<ObjectB>(new
ListDataProvider<ObjectB>(object.getObjectBList()),new TextCell());
               }
               else if (value instanceof ObjectB)
               {
                       ObjectB object  = (ObjectB)value;
                       return new DefaultNodeInfo<ObjectC>(new
ListDataProvider<ObjectC>(object.getObjectCList()),new TextCell());
               }
               String type = value.getClass().getName();
               throw new IllegalArgumentException("Unsupported object type: "+
type);
       }


getObjectBList(),getObjectCList() return the List of the child
Objects.

I pass this model to the CellTree and the CellTree is displayed
correctly.

Now I try to add a new ObjectB instance to the list of ObjectBs in the
one of the ObjectA instances. In order to update the CellTree I have
to update the DataProvider. I define a updateData function in the
CustomTreeModel:

public void updateData(List<ObjectA> objects){
               listDataProvider.setList(objects);  //listDataProvider of the root
node level is stored in the CustomTreeModel
               listDataProvider.refresh(); //probably not necessary as setList
already takes care of refreshing the Tree.
}


Now when I call this method and pass the List of ObjectA instances
(one of them has modified List of ObjectB instances). the CellTree
doesn't get updated/refreshed.

My assumption is that listDataProvider.setList() only checks the List
of ObjectAs and as I haven't changed anything in the root list but in
one of its client lists, the CellTree doesn't get updated. One
workaround is that I call listDataProvider.setList(new
ArrayList<ObjectA>()) (empty list) before calling setList with the
actual list. However this causes the CellTree Nodes to get collapsed,
which I want to avoid.

Another approach would be to store the DataProviders for the ObjectB
and ObjectC instances (which I now only create as a local variable and
pass it to new DefaultNodeInfo) in the CustomTreeModel and also call
setList() on them. But IMHO that's not a really nice way of solving
it.


So basically there are two questions:

1.)  When does setList() on the DataAdapter cause the Display to
refresh it contents? ( I assume that setList() will only call refresh
if the amount of elements is changed -> that's the reason why using
the workaround with a new empty ArrayList worked). What happens, if I
only change one of the properties? How can I force the DataAdapter to
update the Display if the amount of elements doesn't change ?

2.) How can I map an object graph (parent -> client objects) to a
CellTree or CellBrowser, so that any change to one of the client
objects causes a refresh of the Display (CellTree).

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