Adding an array of objects to a JComboBox

Question

Hi hope someone can help I have searched the forums and cannot find any previous questions that cover this.
Basically I want to construct a JComboBox and instead of populating the ComboBox with strings Im wanting to add check boxes.
First Question can this actually be done?
Second Question how?
I have included a sample of the code to show what i mean.
JCheckBox[] layerChecks = new JCheckBox[numberLayers];
for(int i =0; i<numberLayers; i++)
layerChecks[i] = new JCheckBox();
layerChecks.setText(nameLayers[i]);
JComboBox layersComboBox = new javax.swing.JComboBox(layerChecks);
add(layersComboBox);
Any help is much appreciated.

Answer 1

Whenever something like this crops up, you should do a double check
to see of what you are trying to do makes sense.
I'm not saying it doesn't, but from a user point of view, a combo box
with checkboxes is something a user hasn't seen before, so they might not like it.
I've recently done some combo box stuff. What I did was:
subclass MetalComboBoxUI (and WindowsComboBoxUI and MotifComboBoxUI).
In the createPopup() method of the UI create a BasicComboPopup (or MotifCalendarPopup). The BasicComboPopup is a subclass of JPopupMenu, that uses a JList so you do a popup.removeAll() to get rid of the list, then add your item(s) to the popup.
...works for me !
infact here is the basic structure. You'll need to modify to make it
more general purpose.
import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.plaf.ComboBoxUI;
import javax.swing.plaf.basic.ComboPopup;
import javax.swing.plaf.basic.BasicComboPopup;
import javax.swing.plaf.metal.MetalComboBoxUI;
import com.sun.java.swing.plaf.motif.MotifComboBoxUI;
import com.sun.java.swing.plaf.windows.WindowsComboBoxUI;
public class CheckBoxCombo extends JComboBox {
    public CheckBoxCombo() {
        super();
    public void updateUI() {
        ComboBoxUI cui = (ComboBoxUI) UIManager.getUI(this);
        if (cui instanceof MetalComboBoxUI) {
            cui = new MyMetalComboBoxUI();
        } else if (cui instanceof MotifComboBoxUI) {
            cui = new MyMotifComboBoxUI();
        } else if (cui instanceof WindowsComboBoxUI) {
            cui = new MyWindowsComboBoxUI();
        setUI(cui);
     * You probably don't want to populate the popup here...
    protected void setupPopup(BasicComboPopup popup) {
        popup.removeAll();
        popup.add(new JCheckBoxMenuItem("One", false));
        popup.add(new JCheckBoxMenuItem("Two", true));
        popup.add(new JCheckBoxMenuItem("Three", false));
    class MyMetalComboBoxUI extends MetalComboBoxUI {
        protected ComboPopup createPopup() {
            BasicComboPopup popup = new BasicComboPopup(this.comboBox);
            setupPopup(popup);
            return popup;
    class MyWindowsComboBoxUI extends WindowsComboBoxUI {
        protected ComboPopup createPopup() {
            BasicComboPopup popup = new BasicComboPopup(this.comboBox);
            setupPopup(popup);
            return popup;
    class MyMotifComboBoxUI extends MotifComboBoxUI {
        class MotifCalendarPopup extends MotifComboBoxUI.MotifComboPopup {
            public MotifCalendarPopup(JComboBox box) {
                super(box);
        protected ComboPopup createPopup() {
            MotifCalendarPopup popup =
                    new MotifCalendarPopup(this.comboBox);
            setupPopup(popup);
            return popup;
    public static void main(String[] args) {
        //        String defaultLAF = UIManager.getSystemLookAndFeelClassName();
        //        try {
        //            UIManager.setLookAndFeel(defaultLAF);
        //        } catch (Exception e) {
        //            e.printStackTrace();
        JFrame f = new JFrame();
        final CheckBoxCombo cc = new CheckBoxCombo();
        cc.setEditable(false);
        JPanel enablePanel = new JPanel();
        ButtonGroup buttonGroup = new ButtonGroup();
        JRadioButton b = new JRadioButton(new AbstractAction("Enabled") {
                                              public void actionPerformed(
                                                      ActionEvent e) {
                                                  cc.setEnabled(true);
        buttonGroup.add(b);
        enablePanel.add(b);
        b.setSelected(true);
        b = new JRadioButton(new AbstractAction("Disabled") {
                                 public void actionPerformed(
                                         ActionEvent e) {
                                     cc.setEnabled(false);
        buttonGroup.add(b);
        enablePanel.add(b);
        f.getContentPane().add(enablePanel, BorderLayout.NORTH);
        f.getContentPane().add(cc);
        f.pack();
        f.show();