public void onModuleLoad() { final ScrollPanel contentPanel = new ScrollPanel(); contentPanel.setStyleName("content_panel"); RoundedPanel roundedContentPanel = new RoundedPanel(contentPanel, RoundedPanel.ALL, 5); roundedContentPanel.setStyleName("rounded_content_panel"); MenuBar menuBar = createMenuBar(contentPanel); RoundedPanel roundedMenuBar = new RoundedPanel(menuBar, RoundedPanel.ALL, 5); RootPanel.get().add(roundedMenuBar); RootPanel.get().add(roundedContentPanel); }