<zk>
<zscript><![CDATA[
import org.zkoss.zul.*;
import java.util.ArrayList;
DefaultTreeNode r = new DefaultTreeNode("root",new ArrayList());
DefaultTreeNode n1 = new DefaultTreeNode("Node 1",new ArrayList());
DefaultTreeNode n2 = new DefaultTreeNode("Node 2",new ArrayList());
DefaultTreeNode n3 = new DefaultTreeNode("Node 3",new ArrayList());
DefaultTreeNode n4 = new DefaultTreeNode("Node 4");
	
r.add(n1);
n1.add(n2);
n2.add(n3);
n3.add(n4);
	           
DefaultTreeModel model = new DefaultTreeModel(r);
model.addOpenObject(n1);
model.addOpenObject(n2);
model.addOpenObject(n3);
	
import org.zkoss.zul.DefaultTreeNode;
import org.zkoss.zul.Treecell;
import org.zkoss.zul.Treeitem;
import org.zkoss.zul.TreeitemRenderer;
import org.zkoss.zul.Treerow;

public class TestTreeRenderer implements TreeitemRenderer{

	public void render(Treeitem item, Object data, int index) throws Exception{
		final DefaultTreeNode node = (DefaultTreeNode) data;
		final Treerow treeRow = new Treerow();
		item.appendChild(treeRow);
		treeRow.appendChild(new Treecell(node.getData().toString()));
	}
}
TestTreeRenderer trr = new TestTreeRenderer();
]]></zscript>
	<label multiline="true">
		1. click on "add New Child Node", will see a NullPointerException message showed.
	</label>
	<button label="add New Child Node" onClick='n1.add(new DefaultTreeNode("New Child Node"))'/>
	<separator/>
	Template Case:
	<tree model="${model}">
		<treecols visible="false">
			<treecol label="Unit"></treecol>
		</treecols>
		<template name="model">
			<treeitem>
				<treerow>
					<treecell label="${each.data}"/>
				</treerow>
			</treeitem>
		</template>
	</tree>
	ItemRenderer Case:
	<tree model="${model}" itemRenderer="${trr}">
		<treecols visible="false">
			<treecol label="Unit"></treecol>
		</treecols>
	</tree>
</zk>