Looking For JComboBox Help

Question

(Sorry about the lack of rendered tags. I don't know how to use them in this forum.)
I have a JComboBox (a drop menu) that when opened clears all its items and then adds new items from a list. Whenever the list is augmented (and is small), the JComboBox's display size is too small, and it creates a little scrollbar to accomodate. When the popmenu is closed and reopened, the menu is normal. The problem is that when I open the menu after adding a new item to a list, I have to triple click the JComboBox to make it display correctly.
Numbers 2 and 4 are unwanted displays.
<img src="http://img.photobucket.com/albums/v251/Trinithis/dynamicDrive/jcombobox.jpg" />
I could fix it by having the button itself change the contents of the JComboBox (instead of popupMenuWillBecomeVisible()), but I want to have lazy evaluation for it because in my actual program the ArrayList will have to be sorted each time and the JComboBox will have to re-add all its contents. I suppose this is always an option, but I would like to know how to do it this or some other way.
<pre>
import javax.swing.*;
import javax.swing.event.*;
import java.util.*;
import java.awt.*;
import java.awt.event.*;
public class GUI extends JFrame implements ActionListener, PopupMenuListener {
     private JButton bAdd = new JButton("Add");
     private JComboBox jcb = new JComboBox();
     private ArrayList<String> items = new ArrayList<String>(10);
     private int addCount = 0;
     public GUI() {
          Container c = this.getContentPane();
          c.setLayout(new FlowLayout());
          bAdd.addActionListener(this);
          jcb.addPopupMenuListener(this);
          c.add(bAdd);
          c.add(jcb);
          this.setSize(200, 100);
          this.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
          this.setVisible(true);
     public void actionPerformed(ActionEvent e) {
          Object source = e.getSource();
          if(source==bAdd) items.add("Item #" + addCount++);
     public void popupMenuWillBecomeVisible(PopupMenuEvent e){
          Object source = e.getSource();
          if(source==jcb) {
               jcb.removeAllItems();
               for(int i=0; i<items.size(); ++i) jcb.addItem(items.get(i));
     public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {}
     public void popupMenuCanceled(PopupMenuEvent e) {}
     public static void main(String[] args) {
          new GUI();
</pre>
Edited by: Trinithis on Sep 21, 2007 11:18 AM
Edited by: Trinithis on Sep 21, 2007 11:29 AM
Edited by: Trinithis on Sep 21, 2007 11:33 AM
Edited by: Trinithis on Sep 21, 2007 11:34 AM

Answer 1

try it a different way (not using the popupListener)
public GUI() {
Container c = this.getContentPane();
c.setLayout(new FlowLayout());
bAdd.addActionListener(this);
jcb.setUI(new javax.swing.plaf.metal.MetalComboBoxUI(){
  protected JButton createArrowButton(){
    JButton btn = super.createArrowButton();
    btn.addMouseListener(new MouseAdapter(){
      public void mousePressed(MouseEvent me){
        if(jcb.getModel().getSize() < items.size()){
          DefaultComboBoxModel model = new DefaultComboBoxModel();
          for(int i=0; i<items.size(); ++i){
            model.addElement(items.get(i));
          jcb.setModel(model);
    return btn;
//jcb.addPopupMenuListener(this);the tags you're looking for are
[code]
paste code here
[/code]