In the evolution of the Ext GWT (GXT) framework, there seemed to have been some change as to how selection events of trees/tree grids can be intercepted. In release 2.2.1, the following approach works:
treeGrid.getSelectionModel().addSelectionChangedListener(new SelectionChangedListener<ModelData>() {
@Override
public void selectionChanged(SelectionChangedEvent<ModelData> se) {
GWT.log(“selection changed from getSelectionModel”);
}
});
The following approaches do not work:
store.addListener(Events.SelectionChange, new SelectionChangedListener<TreeModel>() {
@Override
public void selectionChanged(SelectionChangedEvent<TreeModel> se) {
GWT.log(“selection changed”);
}
});
treeGrid.addListener(Events.SelectionChange, new SelectionChangedListener<TreeModel>() {
@Override
public void selectionChanged(SelectionChangedEvent<TreeModel> se) {
GWT.log(“selection changed”);
}
});
Resources:
TreeBinder JavaDoc – TreeBinder seems to be deprecated, use selection model instead.
The Full Stack Blog 
To detect when the user selects a node in a tree , you need to register a tree selection listener. Here is an example, taken from the