What are the patterns in communication between View and Presenter in MVP?

Question

Reading about MVP pattern I found there are two communication patterns between View and Presenter:

• View doesn't know Presenter but provides UI controls implementing HasClickHandler interface where Presenter registers its event handlers.

• View knows Presenter , particularly it knows handler method names in Presenter, eg, when a Submit button is clicked in View, a view calls a onSubmitButtonClicked() public method in Presenter.

I found the latter to be easier for JUnit testing, because I can directly simulate submitting event to Presenter. However, my understanding was that the View should not know about the Presenter.

The third approach to resolve the trade-off is to let the Presenter registers event handlers in the View's controls, where the handlers calls public Presenter methods:

public void bind() {
  display.getSubmitButton().addClickHandler(new ClickHandler() {

    @Override
    public void onClick(ClickEvent event) {
      onSubmitButtonClicked();              
    }
  });
}

But this introduces a lot of boilerplate code.

What is the right pattern for View-Presenter communication?

Answer 1

I'm still trying to learn this stuff myself, but the way I'm thinking about it now is something like this:

public interface View {
    void registerMouseListener(MouseListener listener);
}

public class ViewImpl implements View {
    SomeComponent component; // SomeComponent extends java.awt.Component

    public void registerMouseListener(MouseListener listener) {
        component.addMouseListener(listener);
    }
}

Then you can let the Presenter decide however it wants to register for these events, by adding anonymous listeners, or extending MouseListener itself, etc.