import java.awt.Dimension;
import java.awt.Graphics;
import javax.swing.Icon;
import javax.swing.JToggleButton;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeCellRenderer;
import javax.swing.tree.DefaultTreeModel;

/**
 *
 * @author remi
 */
public class JExpander extends JToggleButton {

//  public static void main(String[] args) {
//    try {
//      UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
//    } catch (Exception e) {
//      Logger.getAnonymousLogger().log(Level.SEVERE, null, e);
//    }
//    JFrame f = new JFrame();
//    f.setLayout(new BorderLayout());
//    f.setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
//
//    JExpander e = new JExpander();
//    e.setText("bla");
//
//    f.add(e, BorderLayout.CENTER);
//    f.pack();
//
//    f.setVisible(true);
//  }

  // <editor-fold defaultstate="collapsed" desc="tree renderer">
  private final DefaultMutableTreeNode node = new DefaultMutableTreeNode(null, true);

  private final DefaultTreeModel treeModel = new DefaultTreeModel(node);

  private final JTree tree = new JTree(treeModel);

  private static class TreeCellRendererImpl extends DefaultTreeCellRenderer {

    @Override
    public Icon getIcon() {
      return null;
    }
  }

  {
    tree.setRootVisible(true);
    tree.setShowsRootHandles(true);
    tree.setCellRenderer(new TreeCellRendererImpl());
  }
  // </editor-fold>

  @Override
  protected void paintComponent(Graphics g) {

    DefaultMutableTreeNode child = new DefaultMutableTreeNode();
    node.setUserObject(getText());
    node.add(child);
    treeModel.nodeStructureChanged(node);

    tree.setBounds(getBounds());

    if (isSelected()) {
      tree.expandRow(0);
    } else {
      tree.collapseRow(0);
    }

    tree.paint(g);

    node.remove(child);
  }

  @Override
  public Dimension getPreferredSize() {
    node.setUserObject(getText());
    treeModel.nodeStructureChanged(node);

    Dimension s = tree.getPreferredSize();

    s.height += 6;

    return s;
  }
}