public static interface TreeView.RowActivated

Emitted when a row in the TreeView has been activated. Activation occurs when a row in the view is double-clicked, or when Space or Enter are pressed while a row is selected.

In general, you've got the TreeModel and especially its DataColumns visible, so to use TreeView.RowActivated you can just:

 final TreeModel model;
 final DataColumnString column;
 
 view.connect(new TreeView.RowActivated() {
     public void onRowActivated(TreeView source, TreePath path, TreeViewColumn vertical) {
         final TreeIter row;
 
         row = model.getIter(path);
 
         ... = model.getValue(row, column);
     }
 });
 

Remember that TreeIters and TreePaths are not stable over changes to the model, so get on with using path right away.

TreeView.RowActivated is perfectly sufficient for basic situations, but you may need to see TreeSelection's TreeSelection.Changed to for more complicated selection and activation expressions. In practise you'll use both.