Widgets added in constructor fail to send gwt event by HandlerManager

Hi

I have two panel.

Panel A contains labels with onClick event definition. It will send custom GWT event to Panel B to modify the appearance of Panel B.

The event bus is defined on their parent panel, outside of constructor.
private HandlerManager eventBus= new HandlerManager(this);

The labels and its onClick event definition, created by the constructor of Panel A, fail to send GWT event. I have put the breakpoints on the eventbus handler. No event is received.

The labels and their onClick, created by other methods but not the constructor, have sent the gwt events to the eventbus handler.

Is there any relationship or the order restriction, e.g the completion of the constructor, on defining the eventbus and using it to send gwt event?

Thanks