GWT Cell Tree - leaf nodes - gwt

Question

I'm using a cell tree and I have this problem:
I get the data via RPC calls. I decide if a node is a leaf or not - based on the data that I get for its children. For example - if a node has a son called "foo" - then this node should be a leaf.
I don't know how to make this node to be a leaf and not to show its children on the tree. (instead, I want to show them somewhere else, when clicking on the node)
Is it possible? Does anyone have an idea?
Please help me, I'm stuck with it for 2 days...
Thanks!

Answer 1

You can override isLeaf() method to return true or false.
There will be a problem, however, from the UI perspective. Before a user clicks on a node, you don't know if this should be a node or a leaf. This is a little confusing, although I saw such implementations more than once. If your tree is not very large, consider loading all data at once, and then building it the way you want - creating nodes or leafs as necessary.

Answer 2

If each node has a type, could you create some list or map of types that aren't expected to have children in your TreeViewModel impl?
In an impl I did I used a meta-model for all types, but it's not a requirement.
E.g.,
#Override
public boolean isLeaf(Object value) {
boolean result = true;
if (value == null) {
result = false; // assumes all root nodes have children
} else if (value instanceof NavNode) {
final NavNode currentNode = (NavNode) value;
final NodeType currentNodeType = NodeType.fromValue(currentNode.getType());
if (currentNode.hasChildren() || NodeHelper.couldHaveChildren(currentNodeType)) {
result = false;
}
}
return result;
}
// Create a data provider for root nodes
protected ListDataProvider<NavNode> getDataProvider(Collection<NavNode> rootNodes) {
return new ListDataProvider<NavNode>(new LinkedList<NavNode>(rootNodes));
}
// Create a data provider that contains the immediate descendants.
protected AsyncDataProvider<NavNode> getDataProvider(final NavNode node) {
return new AsyncDataProvider<NavNode>() {
#Override
protected void onRangeChanged(final HasData<NavNode> display) {
final Set<NavNode> clientNodes = util.getAncestorNodes(node);
clientNodes.add(node);
final NavigationInfo clientInfo = new NavigationInfo(clientNodes);
navigationService.getNavInfo(clientInfo, node, resources, qualifications, new SafeOperationCallback<NavigationInfo>(eventBus, false) {
#Override
public void onFailureImpl(Throwable caught) {
GWT.log("Something went wrong retreiving children for " + node.getName(), caught);
updateRowCount(0, false);
}
#Override
public void onSuccessImpl(OperationResult<NavigationInfo> or) {
util.mergeNavInfo(or.getResult());
final NavNode nodeFromServer = util.getNode(node.getId());
final Range range = display.getVisibleRange();
final int start = range.getStart();
final Set<NavNode> nodes = util.getNodes(nodeFromServer.getChildren());
updateRowData(display, start, new LinkedList<NavNode>(nodes));
}
});
}
};
}
private static class NodeHelper {
private static final Set<NodeType> PARENTAL_NODE_TYPES;
static {
PARENTAL_NODE_TYPES = new HashSet<NodeType>();
PARENTAL_NODE_TYPES.add(NodeType.ASSET_OWNER);
PARENTAL_NODE_TYPES.add(NodeType.OPERATING_DAY);
PARENTAL_NODE_TYPES.add(NodeType.RESOURCES);
PARENTAL_NODE_TYPES.add(NodeType.RESOURCE);
PARENTAL_NODE_TYPES.add(NodeType.ENERGY);
PARENTAL_NODE_TYPES.add(NodeType.RESERVE);
PARENTAL_NODE_TYPES.add(NodeType.DAY_AHEAD_CLEARED_OFFERS);
PARENTAL_NODE_TYPES.add(NodeType.DRR_LOAD_FORCAST);
PARENTAL_NODE_TYPES.add(NodeType.RESERVE_DISPATCH);
PARENTAL_NODE_TYPES.add(NodeType.RESERVE_RAMP_RATE);
}
public static boolean couldHaveChildren(NodeType nodeType) {
boolean result = false;
if (PARENTAL_NODE_TYPES.contains(nodeType)) {
result = true;
}
return result;
}
}
}