JTreeのセルエディタにJComboBoxなどを配置したJPanelを使用する

class PluginCellEditor extends DefaultCellEditor {
  private final PluginPanel panel;
  private transient Node node;

  public PluginCellEditor(JComboBox<String> comboBox) {
    super(comboBox);
    panel = new PluginPanel(comboBox);
  }

  @Override public Component getTreeCellEditorComponent(
      JTree tree, Object value, boolean selected, boolean expanded,
      boolean leaf, int row) {
    Node node = panel.extractNode(value);
    panel.setContents(node);
    this.node = node;
    return panel;
  }

  @Override public Object getCellEditorValue() {
    Object o = super.getCellEditorValue();
    if (node == null) {
      return o;
    }
    DefaultComboBoxModel<String> m =
        (DefaultComboBoxModel<String>) panel.comboBox.getModel();
    Node n = new Node(panel.pluginName.getText(), node.plugins);
    n.setSelectedPluginIndex(m.getIndexOf(o));
    return n;
  }

  @Override public boolean isCellEditable(EventObject e) {
    Object source = e.getSource();
    if (!(source instanceof JTree) || !(e instanceof MouseEvent)) {
      return false;
    }
    JTree tree = (JTree) source;
    MouseEvent me = (MouseEvent) e;
    TreePath path = tree.getPathForLocation(me.getX(), me.getY());
    if (path == null) {
      return false;
    }
    Object node = path.getLastPathComponent();
    if (!(node instanceof DefaultMutableTreeNode)) {
      return false;
    }
    Rectangle r = tree.getPathBounds(path);
    if (r == null) {
      return false;
    }
    Dimension d = panel.getPreferredSize();
    r.setSize(new Dimension(d.width, r.height));
    if (r.contains(me.getX(), me.getY())) {
      showComboPopup(tree, me);
      return true;
    }
    return delegate.isCellEditable(e);
  }

  private void showComboPopup(final JTree tree, final MouseEvent me) {
    EventQueue.invokeLater(new Runnable() {
      @Override public void run() {
        Point pt = SwingUtilities.convertPoint(tree, me.getPoint(), panel);
        Component o = SwingUtilities.getDeepestComponentAt(panel, pt.x, pt.y);
        if (o instanceof JComboBox) {
          panel.comboBox.showPopup();
        } else if (o != null) {
          Container c = SwingUtilities.getAncestorOfClass(
              JComboBox.class, (Component) o);
          if (c instanceof JComboBox) {
            panel.comboBox.showPopup();
          }
        }
      }
    });
  }
}