ZK: tree, model is nulll

Question

I am working on zk tree by extending DefaultTreeModel. it's properly renders on webpage. But when I try to get the model associated with this tree using root, i am getting null.

I am using two ways to do that. 1. using Tree hierarchyTree; hierarchyTree.getModel().getRoot(); // returns null 2. using AdvancedTreeModel contactTreeModel extends DefaultTreeModel; ContactTreeNode nodes2 = (ContactTreeNode) contactTreeModel.getRoot(); //also return null

Can you plz, tell me how can I get the root node, or model associate with it, which is not null. So that I can iterate over it.

AdvanceTeeModel.java

package demo.tree.dynamic_tree;

import org.zkoss.zul.DefaultTreeModel;
import org.zkoss.zul.DefaultTreeNode;

import demo.data.pojo.Contact;

public class AdvancedTreeModel extends DefaultTreeModel<Contact> {
    private static final long serialVersionUID = -5513180500300189445L;

    DefaultTreeNode<Contact> _root;

    public AdvancedTreeModel(ContactTreeNode contactTreeNode) {
        super(contactTreeNode);
        _root = contactTreeNode;
    }

    /**
     * remove the nodes which parent is <code>parent</code> with indexes
     * <code>indexes</code>
     * 
     * @param parent
     *            The parent of nodes are removed
     * @param indexFrom
     *            the lower index of the change range
     * @param indexTo
     *            the upper index of the change range
     * @throws IndexOutOfBoundsException
     *             - indexFrom < 0 or indexTo > number of parent's children
     */
    public void remove(DefaultTreeNode<Contact> parent, int indexFrom, int indexTo) throws IndexOutOfBoundsException {
        DefaultTreeNode<Contact> stn = parent;
        for (int i = indexTo; i >= indexFrom; i--)
            try {
                stn.getChildren().remove(i);
            } catch (Exception exp) {
                exp.printStackTrace();
            }
    }

    public void remove(DefaultTreeNode<Contact> target) throws IndexOutOfBoundsException {
        int index = 0;
        DefaultTreeNode<Contact> parent = null;
        // find the parent and index of target
        parent = dfSearchParent(_root, target);
        if(parent!=null){
        for (index = 0; index < parent.getChildCount(); index++) {
            if (parent.getChildAt(index).equals(target)) {
                break;
            }
        }
            remove(parent, index, index);
        }
    }

    /**
     * insert new nodes which parent is <code>parent</code> with indexes
     * <code>indexes</code> by new nodes <code>newNodes</code>
     * 
     * @param parent
     *            The parent of nodes are inserted
     * @param indexFrom
     *            the lower index of the change range
     * @param indexTo
     *            the upper index of the change range
     * @param newNodes
     *            New nodes which are inserted
     * @throws IndexOutOfBoundsException
     *             - indexFrom < 0 or indexTo > number of parent's children
     */
    public void insert(DefaultTreeNode<Contact> parent, int indexFrom, int indexTo, DefaultTreeNode<Contact>[] newNodes)
            throws IndexOutOfBoundsException {
        DefaultTreeNode<Contact> stn = parent;
        for (int i = indexFrom; i <= indexTo; i++) {
            try {
                stn.getChildren().add(i, newNodes[i - indexFrom]);
            } catch (Exception exp) {
                throw new IndexOutOfBoundsException("Out of bound: " + i + " while size=" + stn.getChildren().size());
            }
        }
    }

    /**
     * append new nodes which parent is <code>parent</code> by new nodes
     * <code>newNodes</code>
     * 
     * @param parent
     *            The parent of nodes are appended
     * @param newNodes
     *            New nodes which are appended
     */
    public void add(DefaultTreeNode<Contact> parent, DefaultTreeNode<Contact>[] newNodes) {
        DefaultTreeNode<Contact> stn = (DefaultTreeNode<Contact>) parent;

        for (int i = 0; i < newNodes.length; i++)
            stn.getChildren().add(newNodes[i]);

    }

    private DefaultTreeNode<Contact> dfSearchParent(DefaultTreeNode<Contact> node, DefaultTreeNode<Contact> target) {
        if (node.getChildren() != null && node.getChildren().contains(target)) {
            return node;
        } else {
            int size = getChildCount(node);
            for (int i = 0; i < size; i++) {
                DefaultTreeNode<Contact> parent = dfSearchParent((DefaultTreeNode<Contact>) getChild(node, i), target);
                if (parent != null) {
                    return parent;
                }
            }
        }
        return null;
    }

}

Actually I am using this example, [http://www.zkoss.org/zkdemo/tree/dynamic_tree][Dynamic Tree from ZK]

And in Composer's override render method i am using following line of code to get the root/model from the tree.

ContactTreeNode nodes = (ContactTreeNode) hierarchyTree.getModel().getRoot();
            System.out.println("nodes: " + nodes);

            ContactTreeNode nodes2 = (ContactTreeNode) contactTreeModel.getRoot();

Answer 1

Your remove method have to care about removing the root.
Means, if you remove the root, you have to set a new one.
Try if is solves the problem. Or try if the problem occurs
right after initialization of (and without editing) the tree.