Special rendering for JTree's nodes

Question

Hello all :)
I have a tree that can possibly contain a large number of nodes, so solutions proposed have to consider a certain speed / memory factor also.
Basicly I have a tree representing elements that have many different properties. To help users visually, I do lots of custom rendering like changing color / style of the font depending on the element's nature, and adding special icons.
The thing is, I would like to have more than one icon (possibly two or more) displayed for the user to have a quick visual reminder of certain properties of this element. The only drawback to this is that certain elements will have no icon, and others might have 2 or 3, so the text isnt aligned anymore.
One solution I thought of is maybe I should put these icons to the right of the text? In both cases (left or right of text), how can I do that?
Thanks!

Answer 1

Very interesting! I tried a couple things, here's the modified example, now it shows the current selection. Many thanks to asjf again :
import javax.swing.*;
import javax.swing.tree.*;
import javax.swing.border.Border;
import java.awt.*;
import java.net.*;
import java.util.*;
public class TreeTest2 {
    public static void main(String [] arg) throws Exception {
        long start = System.currentTimeMillis();
        JFrame frame = new JFrame("JTreeTextNodes");
        Random r = new Random();
        DefaultMutableTreeNode root = new DefaultMutableTreeNode(new Integer(r.nextInt(8)));
        for(int i=0; i<50; i++) {
            root.add(new DefaultMutableTreeNode(new Integer(r.nextInt(8))));
        DefaultTreeModel model = new DefaultTreeModel(root);
        JTree tree = new JTree(model);
        tree.setCellRenderer(new MyRenderer());
        frame.getContentPane().add(new JScrollPane(tree));
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.pack();
        frame.show();
        System.out.println(System.currentTimeMillis()-start);
    static class MyNode extends JPanel {
        private static final Border selBorder, unselBorder;
        private static final Color selColor, unselColor;
        static {
            selBorder = BorderFactory.createLineBorder(UIManager.getColor("Tree.selectionBorderColor"));
            unselBorder = BorderFactory.createLineBorder(UIManager.getColor("Tree.textBackground"));
            selColor = UIManager.getColor("Tree.selectionBackground");
            unselColor = UIManager.getColor("Tree.textBackground");
        JLabel nameLbl;
        public MyNode(String name, Icon [] icons) {
            super(new FlowLayout(FlowLayout.RIGHT));
            setBackground(UIManager.getColor("Tree.textBackground"));
            nameLbl = new JLabel(name);
            add(nameLbl);
            for(int j=0; j<icons.length; j++)
                add(new JLabel(icons[j]));
        public void setName(String newName) {
            nameLbl.setText(newName);
        public void setSelected(boolean sel) {
            if (sel) {
                setBackground(selColor);
                setBorder(selBorder);
            } else {
                setBackground(unselColor);
                setBorder(unselBorder);
    static class MyRenderer extends DefaultTreeCellRenderer {
        Icon [][] random;
        int cpt = 0;
        MyNode myNode;
        public MyRenderer() {
            try {
                String http = "http://developer.java.sun.com/developer/techDocs/hi/repository/graphicsRepository/toolbarButtonGraphics/development/";
                Icon i1 = new ImageIcon(new URL(http+"Application24.gif"));
                Icon i2 = new ImageIcon(new URL(http+"WebComponent24.gif"));
                Icon i3 = new ImageIcon(new URL(http+"Jar24.gif"));
                random = new Icon [8][];
                for(int j=0; j<8; j++) {
                    ArrayList l = new ArrayList();
                    if((j&1)==0) l.add(i1);
                    if((j&2)==0) l.add(i2);
                    if((j&4)==0) l.add(i3);
                    random[j] = (Icon[]) l.toArray(new Icon [0]);
            } catch( java.net.MalformedURLException mue ) {
                mue.printStackTrace();
            myNode = new MyNode("test", random[0]);
        public Component getTreeCellRendererComponent(JTree tree, Object value,
        boolean isSelected, boolean expanded,
        boolean leaf, int row, boolean hasFocus) {
            DefaultMutableTreeNode node = (DefaultMutableTreeNode) value;
            Object user = node.getUserObject();
            int iconNb = Integer.parseInt(user.toString());
            MyNode panel = new MyNode("Node of type "+user,random[iconNb]);
            panel.setSelected(isSelected);
            return panel;
            myNode.setSelected(isSelected);
            myNode.setName("test " + cpt++);
            return myNode;
}Bare in mind that the node should display a different text for each element (instead of Node type...), but I was too lazy to modify it that much, this is just for learning purposes :P
A couple things I learned from this :
1- I can create the panel right inside the renderer, that's probably how I would do it for a real app. But then, this means the panel would get created each time the node is rendered, which happens alot more often than like asjf was doing, at node creation.
2- I can use the same single instance of the panel for all my rendering purposes. This is kinda odd to me, I thought that if I would use the same instance of MyNode (see the commented out code at the end of the renderer, uncomment it and comment out the MyNode panel =... right above it for it to run) all my nodes would have the same icons and text. How can that be? Anyways, I guess its better as far as memory consuption to use the same instance for all.
3- There seems to be some padding around the node (blank space), it shows especially here. Is it because of the icon size or is there a setting to tell it not to pad so much? I tried JTree's setRowHeight but it cuts the padding only at the bottom, not the top.