FieldUpdater method is called when updating values in the column.
To catch click event, if I am not wrong then MyItemCell is your custom cell. so inside that cell implement onBrowserEvent
event and handle click event there.
public void onBrowserEvent(final Event event) {
// TODO Auto-generated method stub
super.onBrowserEvent(event);
if (DOM.eventGetType(event) == Event.ONCLICK) {
System.out.println("event type -->> " + event.getType());
}
}