Quando clico no JButton, nada acontece. Isso se aplica mesmo a um JScrollPane que eu coloquei (mostra, mas não rola). Por que o JPanel não está na frente? Tenho a sensação de que algo precisa ser substituído. Deveria ser a expansão da peça que não é a flecha? Se sim, como isso é feito?

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import javax.swing.tree.*;

public class test {

public test() {

    JTree tree = createTree();
    tree.setToggleClickCount(0);
    tree.setRowHeight(50);
    tree.setCellRenderer(new PanelRenderer());

    JFrame f = new JFrame();
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.add(new JScrollPane(tree));

    f.setSize(400, 400);
    f.setLocation(200, 200);
    f.setVisible(true);
}

private JTree createTree() {
    int children = 4;
    int grandChildren = 3;
    DefaultMutableTreeNode root = new DefaultMutableTreeNode();
    DefaultMutableTreeNode node;
    for (int j = 0; j < children; j++) {
        node = new DefaultMutableTreeNode();
        root.add(node);
        for (int k = 0; k < grandChildren; k++)
            node.add(new DefaultMutableTreeNode());
    }
    DefaultTreeModel model = new DefaultTreeModel(root);
    return new JTree(model);
}

public static void main(String[] args) {
    new test();
}
}

class PanelRenderer implements TreeCellRenderer {
JPanel panel;

public PanelRenderer() {
    panel = new JPanel(new BorderLayout());
}

public Component getTreeCellRendererComponent(JTree tree, Object value, boolean selected, boolean expanded,
        boolean leaf, int row, boolean hasFocus) {

    panel.add(new JLabel("aloha"), BorderLayout.WEST);
    JButton fg = new JButton("fg");
    panel.add(fg, BorderLayout.EAST);
    fg.addActionListener(new ActionListener() {
        public void actionPerformed(ActionEvent d) {
            System.out.println("hello");
        }
    });
    panel.setPreferredSize(new Dimension(200, 500));
    return panel;
}
}

Isto é para MadProgrammer, que diz que Renderers e Editores fazem uma imagem do que você coloca. Neste exemplo, os JButtons são clicáveis.

import javax.swing.*;
import javax.swing.tree.*;
import java.awt.event.*;
import java.awt.*;
import javax.swing.event.*;
import java.util.*;

public class test extends JFrame {

public test() {
    super("TreeDemo");
    setSize(500, 500);
    JPanel p = new JPanel();
    p.setLayout(new BorderLayout());

    JButton theParent = new JButton("Feature Set #1");
    JButton thefeature = new JButton("sdfdsfds");
    JButton feature2 = new JButton("Second Feature");
    JButton feature3 = new JButton("Third Feature");
    DefaultMutableTreeNode top = new DefaultMutableTreeNode(theParent, true);
    DefaultMutableTreeNode n1 = new DefaultMutableTreeNode(thefeature, true);
    DefaultMutableTreeNode n2 = new DefaultMutableTreeNode(feature2, true);
    DefaultMutableTreeNode n3 = new DefaultMutableTreeNode(feature3, false);

    n1.add(n3);
    top.add(n1);
    top.add(n2);
    JTree tree = new JTree(top);
    p.add(tree, BorderLayout.NORTH);
    getContentPane().add(p);
    TestRenderer tr = new TestRenderer();
    TestEditor1 te = new TestEditor1();

    tree.setEditable(true);
    tree.setCellRenderer(tr);
    tree.setCellEditor(te);
}

public class TestEditor1 implements TreeCellEditor {

    public TestEditor1() {
    }

    public void addCellEditorListener(CellEditorListener l) {
    }

    public void cancelCellEditing() {
    }

    public Object getCellEditorValue() {
        return this;
    }

    public boolean isCellEditable(EventObject evt) {
        if (evt instanceof MouseEvent) {
            MouseEve,nt mevt = (MouseEvent) evt;

            if (mevt.getClickCount() == 1) {
                return true;
            }
        }

        return false;
    }

    public void removeCellEditorListener(CellEditorListener l) {
    }

    public boolean shouldSelectCell(EventObject anEvent) {
        return true;
    }

    public boolean stopCellEditing() {
        return false;
    }

    public Component getTreeCellEditorComponent(JTree tree, Object value, boolean isSelected, boolean expanded,
            boolean leaf, int row) {
        DefaultMutableTreeNode temp = (DefaultMutableTreeNode) value;
        JComponent temp2 = (JComponent) temp.getUserObject();
        return temp2;

    }
}

public class TestRenderer implements TreeCellRenderer {
    transient protected Icon closedIcon;
    transient protected Icon openIcon;

    public TestRenderer() {
    }

    public Component getTreeCellRendererComponent(JTree tree, Object value, boolean selected, boolean expanded,
            boolean leaf, int row, boolean hasFocus) {
        DefaultMutableTreeNode temp = (DefaultMutableTreeNode) value;
        JComponent temp2 = (JComponent) temp.getUserObject();
        temp2.setBackground(UIManager.getColor("Tree.textBackground"));

        return temp2;
    }

    public void setClosedIcon(Icon newIcon) {
        closedIcon = newIcon;
    }

    public void setOpenIcon(Icon newIcon) {
        openIcon = newIcon;
    }
}

public static void main(String args[]){
JFrame frame = new test();
     frame.addWindowListener(new WindowAdapter()
 {
        public void windowClosing(WindowEvent e) 
{
            System.exit(0);
       }
 });  

frame.pack();
    frame.setVisible(true);
}