Custom JTree cell renderers with custom open/close icons

Question

I am wanting to create a custom JTree where it's nodes are JProgressBar's I have this working just like I want it

However you'll notice that it's missing it's open/closed icon, which I also want to be a custom +/- icon instead of the standard expandable folder. Not entirely sure what I'm doing wrong (Just developing the concept at the moment before prettifying the code)

package com.testingarea;

import java.awt.Component;
import java.awt.Graphics;
import java.util.HashMap;

import javax.swing.BoxLayout;
import javax.swing.Icon;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.UIManager;
import javax.swing.plaf.IconUIResource;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeCellRenderer;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeCellRenderer;

public class TestTrees {  

  public static void main(String args[]) {  
    JFrame frame = new JFrame("Tree");  
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    ProgressTreeCellRenderer renderer = new ProgressTreeCellRenderer();

    JProgressBar progressBar = new JProgressBar(0, 100);
    progressBar.setValue(50);
    progressBar.setStringPainted(true);
    DefaultMutableTreeNode top =
        new DefaultMutableTreeNode(progressBar);
    renderer.getNodeMap().put(top, new ProgressTreeCellRenderer2(progressBar));

    createNodes(top, renderer);
    DefaultTreeModel model = new DefaultTreeModel(top);    

    JTree tree = new JTree(model);
    tree.setCellRenderer(renderer);
    JScrollPane pane = new JScrollPane(tree);
    tree.clearSelection();
    frame.getContentPane().add(pane);  
    frame.setSize(250, 250);  
    frame.setVisible(true);  
  }

  private static void createNodes(DefaultMutableTreeNode top, ProgressTreeCellRenderer renderer) {
    JProgressBar progressBar1 = new JProgressBar(0, 100);
    progressBar1.setValue(25);
    progressBar1.setStringPainted(true);
    DefaultMutableTreeNode one =
        new DefaultMutableTreeNode(progressBar1);
    top.add(one);
    renderer.getNodeMap().put(one, new ProgressTreeCellRenderer2(progressBar1));

    JProgressBar progressBar2 = new JProgressBar(0, 100);
    progressBar2.setValue(25);
    progressBar2.setStringPainted(true);
    DefaultMutableTreeNode two =
        new DefaultMutableTreeNode(progressBar2);
    top.add(two);
    renderer.getNodeMap().put(two, new ProgressTreeCellRenderer2(progressBar2));
  }

}

@SuppressWarnings("serial")
class ProgressTreeCellRenderer extends DefaultTreeCellRenderer {

  private HashMap<DefaultMutableTreeNode, ProgressTreeCellRenderer2> nodeMap = new HashMap<DefaultMutableTreeNode, ProgressTreeCellRenderer2>();

  @Override
  public Component getTreeCellRendererComponent(JTree tree, final Object value, boolean selected, boolean expanded, boolean leaf, int row, boolean hasFocus) {
    if(nodeMap.containsKey(value)) {
      //I was expecting this to work, alas it does not?
      setClosedIcon(new IconUIResource(new NodeIcon('+')));
      setOpenIcon(new IconUIResource(new NodeIcon('-')));
      return nodeMap.get(value).getTreeCellRendererComponent(tree, value, selected, expanded, leaf, row, hasFocus);
    }
    return super.getTreeCellRendererComponent(tree, value, selected, expanded, leaf, row, hasFocus);
  }

  public HashMap<DefaultMutableTreeNode, ProgressTreeCellRenderer2> getNodeMap() {
    return nodeMap;
  }
}

class ProgressTreeCellRenderer2 implements TreeCellRenderer {

  private JProgressBar _progressBar;
  private DefaultTreeCellRenderer _defaultRenderer;

  public ProgressTreeCellRenderer2(JProgressBar progressBar) {
    _progressBar = progressBar;
    _defaultRenderer = new DefaultTreeCellRenderer();
  }

  @Override
  public Component getTreeCellRendererComponent(JTree tree, final Object value, boolean selected, boolean expanded, boolean leaf, int row, boolean hasFocus) {
    Component render = _defaultRenderer.getTreeCellRendererComponent(tree, value, selected, expanded, leaf, row, hasFocus);
    final JPanel panel = new JPanel();
    BoxLayout layout = new BoxLayout(panel, BoxLayout.X_AXIS);

    panel.setLayout(layout);
    panel.add(_progressBar);
    render = panel;    
    return render;
  }

}

class NodeIcon implements Icon {

  private static final int SIZE = 9;

  private char type;

  public NodeIcon(char type) {
    this.type = type;
  }

  public void paintIcon(Component c, Graphics g, int x, int y) {
    g.setColor(UIManager.getColor("Tree.background"));
    g.fillRect(x, y, SIZE - 1, SIZE - 1);

    g.setColor(UIManager.getColor("Tree.hash").darker());
    g.drawRect(x, y, SIZE - 1, SIZE - 1);

    g.setColor(UIManager.getColor("Tree.foreground"));
    g.drawLine(x + 2, y + SIZE / 2, x + SIZE - 3, y + SIZE / 2);
    if (type == '+') {
      g.drawLine(x + SIZE / 2, y + 2, x + SIZE / 2, y + SIZE - 3);
    }
  }

  public int getIconWidth() {
    return SIZE;
  }

  public int getIconHeight() {
    return SIZE;
  }
}

Answer 1

In case of ProgressTreeCellRenderer calling setClosedIcon or setOpenIcon has no effect as you are returning another renderer that is retrieved from a nodeMap. You'd have to add the icon in the implementation of ProgressTreeCellRenderer2. For example, try this to add an icon to the panel in ProgressTreeCellRenderer2:

panel.add((new JLabel((Icon)UIManager.get("Tree.closedIcon"))));

However, note that your current implementation is very expensive. Not only you have a new renderer per node, but also, you reallocate the panel instance inside getTreeCellRendererComponent(). Try to use a single renderer for all nodes with preallocated controls where you only update properties based on the arguments of getTreeCellRendererComponent. See How to Use Trees for renderer details and examples of a tree display customization.

Take a look at this answer (by @mKorbel) that illustrates a single progress bar renderer in a table.