JTree TreeNode question

[Tal Tal]

hi
how do i make a TreeNode in a jtree to extand ?

[Craig Wood]

Assuming you are asking how to do this programatically vis–a–vis with the mouse

import java.awt.*;
import java.awt.event.*;
import java.util.Enumeration;
import javax.swing.*;
import javax.swing.tree.*;
 
public class ExpansionTest
{
    TreeNode selectedNode;
 
    public ExpansionTest()
    {
        String[] names =  new String[] {
            // branches |<-- child leaf nodes -->|
            "hawks", "gray", "red-tailed", "rough-legged",
            "falcons", "harrier", "kestrel", "kite", 
            "owls", "barred", "saw-whet", "snowy"
        };
        JTree tree = createTree(names);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(getUIPanel(tree, names), "North");
        f.getContentPane().add(tree);
        f.setSize(400,400);
        f.setLocation(200,200);
        f.setVisible(true);
    }
 
    private void findNode(JTree tree, String name)
    {
        selectedNode = null;
        TreeNode root = (TreeNode)tree.getModel().getRoot();
        findNode(root, name);
    }
 
    private void findNode(TreeNode node, String name)
    {
        String s = node.toString();
        if(name.equals(s))
            selectedNode = node;
        if(node.getChildCount() >= 0)
        {
            Enumeration e = node.children();
            while(e.hasMoreElements())
            {
                TreeNode n = (TreeNode)e.nextElement();
                findNode(n, name);
            }
        }
    }
 
    private void expandNode(JTree tree, TreeNode node, boolean expand)
    {
        if(node.isLeaf())
            return;
        if(node.getChildCount() >= 0)
        {
            Enumeration e = node.children();
            while(e.hasMoreElements())
            {
                TreeNode n = (TreeNode)e.nextElement();
                expandNode(tree, n, expand);
            }
        }
        TreePath path = new TreePath(((DefaultMutableTreeNode)node).getPath());
        if(expand)
            tree.expandPath(path);
        else
            tree.collapsePath(path);
    }
 
    private JTree createTree(String[] names)
    {
        DefaultMutableTreeNode root = new DefaultMutableTreeNode("birds");
        DefaultMutableTreeNode[] nodes = new DefaultMutableTreeNode[names.length];
        for(int j = 0; j < nodes.length; j++)
            nodes[j] = new DefaultMutableTreeNode(names[j]);
        for(int j = 0; j < 9; j += 4)
        {
            root.insert(nodes[j], j % 3);
            for(int k = j + 1; k < j + 4; k++)
                nodes[j].insert(nodes[k], k - j - 1);
        }
        DefaultTreeModel model = new DefaultTreeModel(root);
        return new JTree(model);
    }
 
    private JPanel getUIPanel(final JTree tree, String[] names)
    {
        final JComboBox combo = new JComboBox(names);
        final JButton
            expand = new JButton("expand"),
            collapse = new JButton("collapse");
        ActionListener l = new ActionListener()
        {
            boolean open;
 
            public void actionPerformed(ActionEvent e)
            {
                JButton button = (JButton)e.getSource();
                String s = (String)combo.getSelectedItem();
                if(button == expand)
                    open = true;
                if(button == collapse)
                    open = false;
                findNode(tree, s);
                expandNode(tree, selectedNode, open);
            }
        };
        expand.addActionListener(l);
        collapse.addActionListener(l);
        JPanel panel = new JPanel();
        panel.add(expand);
        panel.add(combo);
        panel.add(collapse);
        return panel;
    }
 
    public static void main(String[] args)
    {
        new ExpansionTest();
    }
}