GWT basic example, does it look ok?

Question

It was suggested I post this here instead of the main forum.

I have an EntryPoint class that does nothing else but load this PanelA class onto the root panel. Does this look like a good starting point for my app. I have a dropdown, a couple of buttons and an image. The onClick configures some fields in the next Panel and then loads it. My question is does this look like something that I could work with now and expand into a more complex UI or have I got the GWT basics all wrong.?

public class PanelA extends HTMLPanel { private static PanelA panel;
private static ListBox list; private static Image image = new Image("images/GB-wp1.jpg");

    private PanelA()
    {
        super("Panel A");
        final RootPanel rootPanel = RootPanel.get();
        list = getListBox();
        add(image);
        image.setSize("100px", "100px");

        SimpleRadioButton simpleRadioButton = new SimpleRadioButton("new name");
        add(simpleRadioButton);
        simpleRadioButton.setSize("51px", "35px");

        NavigationButtonsPanel btnPanel = new NavigationButtonsPanel();
        btnPanel.setForwardHandler(new ClickHandler() {
            public void onClick(ClickEvent event) 
            {
                rootPanel.clear();
                PanelB.setMessageFromPreviousPage("Selected item " + list.getItemText( list.getSelectedIndex() ) + " in Panel A");
                rootPanel.add( PanelB.getInstance() );
            }
        });

        add( list );
        add( btnPanel );
    }

    public static PanelA getInstance()
    {
        if (panel == null)
        {
            panel = new PanelA();
        }
        return panel;
    }

    public static ListBox getListBox()
    {
        ListBox widget = new ListBox();
        widget.addStyleName("demo-ListBox");
        widget.addItem("Quiz 1");
        widget.addItem("Quiz 2");
        widget.addItem("Quiz 3");
        return widget;
    }

}

I should add this app works fine, loads the next panel without any problem. Just want to know is this a correct application of GWT design?