treegrid = new TreeGrid(dataConnector, options);
RootPanel.get("mytreegrid").add(treegrid);
// create a button to add a truck, to see that data is updated
Button btnAddTruck = new Button("Add Truck");
btnAddTruck.addClickHandler(new ClickHandler() {
@Override
public void onClick(ClickEvent event) {
Truck truck = new Truck("Added Truck", 1234, "test");
dataConnector.add(truck);
}