DesktopActivity.java

public class DesktopActivity extends AbstractActivity<IsWidget> {
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    public DesktopActivity() {
        super("Desktop", null);
        logger.info("create new DesktopActivity");

        AppController.getINSTANCE().getClientFactory().getEventBus()
                .addHandler(StartActivityDisplay.TYPE, new StartActivityDisplayEventHandler() {
                    @Override
                    public void onEvent(StartActivityDisplay event) {
                        if (event.getWidget() != null) {
                            DesktopActivity.getContentPanel().clear();
// add view to center ....                          DesktopActivity.getContentPanel().setWidget(event.getWidget());

                        }
                    }
                });
    }

    private static void initView() {
        Viewport p = AppController.getINSTANCE().getClientFactory().getViewport();
        desktopView = new DesktopView();
        p.add(desktopView.asWidget());
        p.forceLayout();

    }

    public static ContentPanel getContentPanel() {
        if (desktopView == null) {
            initView();
        }
        return desktopView.getContentPanel();
    }
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}