I found a kind of solution in another post.
You must override showFeedback in your TreeGridDropTarget.
Then, in the method, you can use
Code:
com.sencha.gxt.widget.core.client.tree.Tree.TreeNode<? extends BaseDto> item = super
.getWidget().findNode(
event.getDragMoveEvent().getNativeEvent().getEventTarget().<Element> cast());
to find the target element, and if you want to forbid the drop, instead of calling the super you call :
Code:
// forbid the drop
status = -1;
activeItem = null;
appendItem = null;
Insert.get().hide();
event.getStatusProxy().setStatus(false);