Problem using StackLayoutPanel

I am having problems using a StackPanel Layout. It does not work. It just shows the headings but no labels. Even the example from the documentation does not work:

http://google-web-toolkit.googlecode.com/svn/javadoc/latest/com/google/gwt/user/client/ui/StackLayoutPanel.html

java:

import com.google.gwt.core.client.GWT;
import com.google.gwt.uibinder.client.UiBinder;
import com.google.gwt.user.client.ui.Composite;
import com.google.gwt.user.client.ui.HasText;
import com.google.gwt.user.client.ui.Widget;

public class NavigationWidget extends Composite implements HasText {

    private static NavigationWidgetUiBinder uiBinder = GWT
            .create(NavigationWidgetUiBinder.class);

    interface NavigationWidgetUiBinder extends
            UiBinder<Widget, NavigationWidget> {
    }

    public NavigationWidget() {
        initWidget(uiBinder.createAndBindUi(this));

    }

    public void setText(String text) {
    }

    public String getText() {
        return null;
    }

}

xml:

<!DOCTYPE ui:UiBinder SYSTEM "http://dl.google.com/gwt/DTD/xhtml.ent">
<ui:UiBinder xmlns:ui="urn:ui:com.google.gwt.uibinder"
    xmlns:g="urn:import:com.google.gwt.user.client.ui">

    <g:HTMLPanel>
        <g:StackLayoutPanel unit='PX'>

            <g:stack>
                <g:header size='30'>
                    People
                </g:header>
                <g:VerticalPanel>
                    <g:Label>People Item 1</g:Label>
                    <g:Label>People Item 2</g:Label>
                    <g:Label>People Item 3</g:Label>
                    <g:Label>People Item 4</g:Label>
                </g:VerticalPanel>
          开发者_开发技巧  </g:stack>

            <g:stack>
                <g:header size='30'>
                    Groups  
                </g:header>
                <g:VerticalPanel>
                    <g:Label>Group Item 1</g:Label>
                    <g:Label>Group Item 2</g:Label>
                    <g:Label>Group Item 3</g:Label>
                    <g:Label>Group Item 4</g:Label>
                </g:VerticalPanel>
            </g:stack>

            <g:stack>
                <g:header size='30'>
                    Settings
                </g:header>
                <g:VerticalPanel>
                    <g:Label>Item 5</g:Label>
                    <g:Label>Item 6</g:Label>
                    <g:Label>Item 7</g:Label>
                    <g:Label>Item 8</g:Label>
                </g:VerticalPanel>
            </g:stack>

        </g:StackLayoutPanel>

    </g:HTMLPanel>
</ui:UiBinder> 

All LayoutPanels must be in a container that implements ProvidesResize, or have their size explicitly set in code. The easiest thing for you to do is set the size of the StackLayoutPanel explicitly: just add height="100%" to your <StackLayoutPanel> element.

For more control, change your Composite base class to ResizeComposite and get rid of the <g:HTMLPanel> element - just make the StackLayoutPanel the root element of your ui.xml file. You'll also have to make sure that you only use the NavigationWidget in other LayoutPanels - for instance, you wouldn't add it to RootPanel.get(), but instead to RootLayoutPanel.get()

For more info, see http://code.google.com/webtoolkit/doc/latest/DevGuideUiPanels.html