Create a PopupMenu when right click onto an item of JComboBox

Question

How do I make so that, a popupmenu appear only when I right click onto a item of JComboBox. What I have right now is showing a PopupMenu whenever I right click on the frame.
I got another question to ask if you guys dont mind. How do I set the ComboBox to scroll horizontally. Right now I set the preferredSize of the ComboBox so if the item's names are too long, it will be cut off. Can I set it so that I can scroll horizontally to see the rest of the item's name?

Answer 1

My English is very poor, so it's hard to explain...
3.
// This is just an example code and has not been tested.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.plaf.basic.*;
public class ComboRightClickTest{
  public JComponent makeUI(final JFrame frame) {
    frame.setGlassPane(new LockingGlassPane());
    String[] items = {"test1", "test2", "test3"};
    JComboBox combo = new JComboBox(items);
    combo.setUI(new BasicComboBoxUI() {
      protected ComboPopup createPopup() {
        return new BasicComboPopup( comboBox ) {
          protected JList createList() {
            return new JList( comboBox.getModel() ) {
              public void processMouseEvent(MouseEvent e)  {
                if(e.isPopupTrigger()) {
                  String s = getSelectedValue().toString();
                  frame.getGlassPane().setVisible(true);
                  final JPopupMenu m = new JPopupMenu();
                  final JMenuItem i = new JMenuItem(
                      new AbstractAction("del:"+s) {
                    public void actionPerformed(ActionEvent ae) {
                      comboBox.removeItemAt(getSelectedIndex());
                      frame.getGlassPane().setVisible(false);
                      m.setVisible(false);
                  i.addMouseListener(new MouseAdapter() {
                    public void mouseEntered(MouseEvent me) {
                      i.setBackground(getSelectionBackground());
                    public void mouseExited(MouseEvent me) {
                      i.setBackground(getBackground());
                  m.add(i);
                  Point p = e.getPoint();
                  SwingUtilities.convertPointToScreen(p, this);
                  m.show(null, p.x, p.y);
                  return;
                super.processMouseEvent(e);
    JPanel p = new JPanel(new BorderLayout());
    p.setBorder(BorderFactory.createEmptyBorder(5,5,5,5));
    p.add(combo, BorderLayout.NORTH);
    p.setPreferredSize(new Dimension(320, 100));
    return p;
  public static void main(String[] args) {
    EventQueue.invokeLater(new Runnable() {
      public void run() { createAndShowGUI(); }
  public static void createAndShowGUI() {
    JFrame f = new JFrame();
    f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
    f.getContentPane().add(new ComboRightClickTest().makeUI(f));
    f.setResizable(false); //XXX
    f.pack();
    f.setLocationRelativeTo(null);
    f.setVisible(true);
class LockingGlassPane extends JComponent {
  public LockingGlassPane() {
    setOpaque(false);
  @Override public void setVisible(boolean isVisible) {
    boolean oldVisible = isVisible();
    super.setVisible(isVisible);
    JRootPane rootPane = SwingUtilities.getRootPane(this);
    if(rootPane!=null && isVisible()!=oldVisible) {
      rootPane.getLayeredPane().setVisible(!isVisible);
  @Override public void paintComponent(Graphics g) {
    JRootPane rootPane = SwingUtilities.getRootPane(this);
    if(rootPane!=null) {
      http://weblogs.java.net/blog/alexfromsun/archive/2008/01/
      rootPane.getLayeredPane().print(g);
    super.paintComponent(g);
}