Combobox in tree with renderer

<?page id="kukatkoPage2" title="Test Tree item"?>

<zk xmlns="http://www.zkoss.org/2005/zul"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xmlns:h="http://www.w3.org/1999/xhtml">
    
    <window title="Test" height="100%" apply="TestController">
        <tree id="tree" width="100%" height="100%" >
            <treecols sizable="true">
                <treecol label="Name" />
                <treecol label="Description" />
            </treecols>
        </tree>
    </window>
</zk>

import java.util.ArrayList;
import java.util.List;
import org.zkoss.zk.ui.Component;
import org.zkoss.zk.ui.util.GenericForwardComposer;
import org.zkoss.zul.AbstractTreeModel;
import org.zkoss.zul.Combobox;
import org.zkoss.zul.Comboitem;
import org.zkoss.zul.Tree;
import org.zkoss.zul.Treecell;
import org.zkoss.zul.Treeitem;
import org.zkoss.zul.TreeitemRenderer;
import org.zkoss.zul.Treerow;




public class TestController extends GenericForwardComposer {

    Tree tree;

    public void doAfterCompose(Component comp) throws Exception {
        super.doAfterCompose(comp);
        comp.setVariable("ctl", this, true);

        String[] name2 = {"Paul","Eric","Gray"};
        String[] accountId2 = {"p002","e009","g019"};
        ArrayList alc2 = new ArrayList();
        for(int i =0; i < name2.length; i++){
            DataItem person = new DataItem(name2<i >,accountId2<i >);
            SimpleTreeNode stn = new SimpleTreeNode(person,new ArrayList());
            alc2.add(stn);
        }

        SimpleTreeNode salesDep = new SimpleTreeNode(new DataItem("Sales",""),alc2);
        ArrayList al = new ArrayList();
        al.add(salesDep);
        SimpleTreeNode root = new SimpleTreeNode("ROOT",al);

        tree.setTreeitemRenderer(new DLTreeItemRenderer());
        tree.setModel(new DLTreeModel(root));
        
    }


    class DataItem{
        private String polozka;
        private String hodnota;
        public DataItem(String polozka, String hodnota) {
            this.polozka = polozka;
            this.hodnota = hodnota;
        }
        public String getHodnota() {return hodnota;}
        public void setHodnota(String hodnota) {this.hodnota = hodnota;}
        public String getPolozka() {return polozka;}
        public void setPolozka(String polozka) {this.polozka = polozka;}
    }

    class DLTreeItemRenderer implements TreeitemRenderer {
        public void render(Treeitem item, Object data) throws Exception {
            SimpleTreeNode t = (SimpleTreeNode) data;
            DataItem person = (DataItem) t.getData();
            Treecell tcName = new Treecell(person.getPolozka());
            Treecell tcEmail = new Treecell();
            Combobox l = new Combobox();
            for (int i = 0; i < 500; i++) {
                Comboitem ci = new Comboitem();
                ci.setValue(i);
                ci.setLabel("Label: " + i);
                ci.setParent(l);
            }
            l.setParent(tcEmail);

            Treerow tr = null;
            if (item.getTreerow() == null) {
                tr = new Treerow();
                tr.setParent(item);
            } else {
                tr = item.getTreerow();
                tr.getChildren().clear();
            }
            tcName.setParent(tr);
            tcEmail.setParent(tr);
            item.setOpen(false);
        }
    }

    class DLTreeModel extends AbstractTreeModel {
        public DLTreeModel(SimpleTreeNode root) {super(root);}
        public Object getChild(Object parent, int index) {
            SimpleTreeNode node = (SimpleTreeNode)parent;
            return node.getChildAt(index);
        }
        public int getChildCount(Object parent) {
            SimpleTreeNode node = (SimpleTreeNode)parent;
            return node.getChildCount();
        }
        public boolean isLeaf(Object node) {
            if(node instanceof SimpleTreeNode){
                SimpleTreeNode node_ = (SimpleTreeNode)node;
                return node_.isLeaf();
            }else{
                return true;
            }
        }
    }

    public class SimpleTreeNode {
        private Object _data;
        private List _children;

        public SimpleTreeNode(Object data, List children){
            _data = data;
            _children = children;
        }
        public Object getData(){return _data;}
        public List getChildren(){return _children;}
        public String toString(){return (_data == null)?"Data is null":_data.toString();}
        public boolean isLeaf(){return (_children.size() == 0);}
        public Object getChildAt(int childIndex){return _children.get(childIndex);}
        public int getChildCount(){return _children.size();}
    }
}