What is the way to handle Click on GWT FlowPanel

What you need to do here is wrap your FlowPanel in a FocusPanel. A FocusPanel contain all possible handler and thus will enable you to have a ClickHandler set to it.

Another method would be to create your own widget extending the flowpanel and implementing the necessary interface in order to be able to contain a ClickHandler.

I personally would recommend the first method. It's simpler, faster to code and won't slow down your application.

Actually, you go for this:

FlowPanel fPanel = new FlowPanel() {
      @Override
      public void onAttach() {
           super.onAttach();
           super.addDomHandler(handler, ClickEvent.getType());  // handler is the instance         
                                                                // of your ClickHandler
      }
}

Cheers!!!