Integration of existing gwt application to liferay protal

[peter tong]

In my gwt module, onModuleLoad() method I write the following code

RootPanel rootPanel = RootPanel.get("uniqueID");
//RootPanel rootPanel = RootPanel.get();
final SplitLayoutPanel splitLayoutPanel = new SplitLayoutPanel();
rootPanel.add(splitLayoutPanel);
splitLayoutPanel.setSize(String.valueOf(Window.getClientWidth()), String.valueOf(Window.getClientHeight()));

I compile the gwt module and copy all file under the directory of *.nocache.js(attachment liferayGwt03.jpg) to demo-portlet/docroot/html/
(attachment liferayGwt02.jpg, demo-portlet is my first portlet example)
and then in docroot/view.jsp, I write the following

<%@ taglib uri="http://java.sun.com/portlet_2_0" prefix="portlet" %>
<script src="<%=request.getContextPath()%>/html/com.mycompany.project.GWTDesignerFirst.nocache.js">
</script>
<div id="uniqueID"></div>
<portlet:defineObjects />

This is the Demo portlet.

but when I run the liferay portal, the rootPanel occupy all the space of the front page of liferay, not inside any portlet window. why?
how to limit its size to within the portlet window?