Växla mellan paneler i GWT

package com.test.client;

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.user.client.ui.RootPanel;
import com.google.gwt.user.client.ui.VerticalPanel;
import com.smartgwt.client.widgets.Button;
import com.smartgwt.client.widgets.events.ClickEvent;
import com.smartgwt.client.widgets.events.ClickHandler;
import com.test.client.MyPanel;

public class Testing implements EntryPoint {

	public void onModuleLoad() {
		final VerticalPanel startPanel = new VerticalPanel();
		Button button = new Button("Click here");
		button.addClickHandler(new ClickHandler() {
			public void onClick(ClickEvent event) {
				RootPanel.get("content").clear();
				MyPanel myPanel = new MyPanel(RootPanel.get("content"), startPanel);
			}
		});
		startPanel.add(button);
		RootPanel.get("content").add(startPanel);
	}
}

package com.test.client;

import com.google.gwt.user.client.ui.Panel;
import com.google.gwt.user.client.ui.VerticalPanel;
import com.google.gwt.user.client.ui.Widget;
import com.smartgwt.client.widgets.Button;
import com.smartgwt.client.widgets.events.ClickEvent;
import com.smartgwt.client.widgets.events.ClickHandler;

public class MyPanel extends Widget{
	
	public MyPanel(final Panel content, final VerticalPanel startPanel){
		VerticalPanel newPanel = new VerticalPanel();
		Button button2 = new Button("Return");
		button2.addClickHandler(new ClickHandler() {
			public void onClick(ClickEvent event) {
				content.clear();
				content.add(startPanel);
			}
		});
		newPanel.add(button2);
		content.add(newPanel);	
	}
	
}