render nothing when using ru.xpoft.vaadin.VaadinView and extends a class

hi, Folks

I am using vaadin 7.1.0 with xpoft addon .
Everything works well until I abstract some methods into an abstract class for serveral Views.
Hope someone can help me solve it.

My abstract class -

public abstract class AbstractView extends Panel implements View {

CssLayout root = new CssLayout();
CssLayout menu = new CssLayout();
CssLayout content = new CssLayout();
private Logger logger = Logger.getLogger("web");
private PortalUI portalUI;
private DiscoveryNavigator contentNavigator;

public void PostConstruct() {
            // render the view ...
    logger.debug(">> build root successfully.");
 .... other stuffs 

Sub Class

public class DashboardView extends AbstractView {

    public static final String NAME = "dashboard";
    private Logger logger = Logger.getLogger("web");

    public void PostConstruct() {
    public void enter(ViewChangeEvent event) {


But it is not what I expect in the end.
When it navigates to DashboardView, I get a blank screen.
In the log, I find “>> build root successfully”. So, the super class is called to build the content.
But why it does not come into the browser afterward ?