GWT Designer with MVP

[bobpardoe]

I am trying to evaluate the latest GWT Designer 7.3

I have a prototype project that has been hand coded. It follows an MVP pattern so that the 'view' element has the ui widgets and the 'presenter' has all the methods \ event handlers etc etc.

The issue that I have is that when I choose to edit the 'view' with the GWT Designer, it stops as it cannot find the entry point.

The issue is that (of course) as this is the view, it wont have one. The entry point is in the 'presenter' file.

Is there any way around this issue ?

[Eric Clayberg]

GWT Designer is designed to edit any of the known GWT UI types like EntryPoints, Composites, PopupPanels and DialogBoxes.

If you provide a complete example of what you are trying to do, we might be able to make some suggestions.

[lowecg]

Hi Eric,

The MVP pattern typically breaks a panel down into a view and a presenter where an interface defines the boundary between the two classes. For example, the following presenter has a simple view containing a text widget and a button:

Code: Select all

public class GreetingPresenter extends WidgetPresenter {

public interface Display extends WidgetDisplay {
  public HasValue getName();

  public HasClickHandlers getSend();
}

@Inject
public GreetingPresenter(final Display display,
                final EventBus eventBus) {
  super(display, eventBus);
 
  bind();
}


@Override
protected void onBind() {
  // 'display' is a final global field containing the Display passed into the constructor.
  display.getSend().addClickHandler(new ClickHandler() {
   public void onClick(final ClickEvent event) {
    doSend();
   }
  });
}


protected void onSend() {
    // do something here
}

public void refreshDisplay() {
  display.getName().setValue("some value");
}

}

Code: Select all

public class GreetingView implements GreetingPresenter.Display {

private final TextBox name;
private final Button sendButton;

public GreetingView() {
  final FlowPanel panel = new FlowPanel();

  name = new TextBox();
  panel.add(name);

  sendButton = new Button("Go");
  panel.add(sendButton);
 
  // Add the nameField and sendButton to the RootPanel
  // Use RootPanel.get() to get the entire body element
  RootPanel.get("nameFieldContainer").add(name);
  RootPanel.get("sendButtonContainer").add(sendButton);
}

public HasValue getName() {
  return name;
}

public HasClickHandlers getSend() {
  return sendButton;
}

public Widget asWidget() {
  return panel;
}

}

An Eclipse project for a very basic MVP application is available from here.

Particular points of interest are in the presenter's refreshDisplay (value pushed to the view) and the onBind method where a button event handler is registered. Additionally, the view and presenter instances are constructed and associated using Google Injector (GIN). Is GWT Designer able to handle code where a panel has been broken out into view construction and associated event handling + other business logic in this way?

Best regards,

Chris.

[DaveL]

A small compromise is to extend Composite in your display classes. GWT Designer would be limited in scope to a layout tool for displays. I don't think a tool can cope with the "interfaces of interfaces" used in the presenters.

[Eric Clayberg]

Is GWT Designer able to handle code where a panel has been broken out into view construction and associated event handling + other business logic in this way?

The basic answer to your question is, no. GWT Designer is designed to edit all of the normal GWT UI classes and their associated common patterns. It knows nothing about this specific framework you are using or its patterns for handling events and other constructs. That said, GWT Designer can edit the GreetingView class as shown below (although I don't understand why it is adding widgets first to the FlowPanel and then again to the RootPanels).

GreetingView.jpg (49.44 KiB) Viewed 848 times