Determine the best width for ListCellRenderer - Multi-column combo box

Question

Currently, I am having a multi column combo box. In order for the column to align properly during show popup, I use box layout to do so. However, the short coming for box layout is that, the size for each column is fixed. This makes me have a difficulty, when I have a long string to be displayed. The problem is shown through the following screen shoot.
http://i.imgur.com/4Nfc6.png
This is because in 2nd column,
1) All the 3 rows must be in same size so that they are aligned.
2) But 1st row and 2nd row cell renderer, do not know 3rd row is holding such a long string.
The code (2 files) to demo this problem is as follow. Is there any way the size of the cell will be adjusted automatically? Yet, all the row will be aligned properly.
ResultSetCellRenderer.java
package javaapplication24;
import java.awt.Color;
import java.awt.Component;
import javaapplication24.NewJFrame.ResultType;
import javax.swing.JList;
import javax.swing.ListCellRenderer;
import javax.swing.UIManager;
* @author yccheok
public class ResultSetCellRenderer extends javax.swing.JPanel implements ListCellRenderer {
    /** Creates new form ResultSetCellRenderer */
    public ResultSetCellRenderer() {
        initComponents();
    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {
        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        setLayout(new javax.swing.BoxLayout(this, javax.swing.BoxLayout.X_AXIS));
        jLabel1.setText("jLabel1");
        jLabel1.setMaximumSize(new java.awt.Dimension(88, 14));
        jLabel1.setMinimumSize(new java.awt.Dimension(88, 14));
        jLabel1.setPreferredSize(new java.awt.Dimension(88, 14));
        add(jLabel1);
        jLabel2.setText("jLabel2");
        jLabel2.setMaximumSize(new java.awt.Dimension(100, 14));
        jLabel2.setMinimumSize(new java.awt.Dimension(200, 14));
        jLabel2.setPreferredSize(new java.awt.Dimension(100, 14));
        add(jLabel2);
    }// </editor-fold>
    // Variables declaration - do not modify
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    // End of variables declaration
    // Do not use static, so that our on-the-fly look n feel change will work.
    private final Color cfc  = UIManager.getColor("ComboBox.foreground");
    private final Color cbc  = UIManager.getColor("ComboBox.background");
    private final Color csfc = UIManager.getColor("ComboBox.selectionForeground");
    private final Color csbc = UIManager.getColor("ComboBox.selectionBackground");
    private final Color cdfc = UIManager.getColor("ComboBox.disabledForeground");
    // For Nimbus look n feel.
    private final Color nimbus_csfc;
         Color c = UIManager.getColor("ComboBox:\"ComboBox.renderer\"[Selected].textForeground");
         // Pretty interesting. Applying "c" directly on the component will not
         // work. I have the create a new instance of Color based on "c" to make
         // it works.
         nimbus_csfc = c != null ? new Color(c.getRed(), c.getGreen(), c.getBlue()) : null;
    private final Color nimbus_csbc;
        Color c = UIManager.getColor("ComboBox:\"ComboBox.renderer\"[Selected].background");
         // Pretty interesting. Applying "c" directly on the component will not
         // work. I have the create a new instance of Color based on "c" to make
         // it works.
        nimbus_csbc = c != null ? new Color(c.getRed(), c.getGreen(), c.getBlue()) : null;
    @Override
    public Component getListCellRendererComponent(JList list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
        final Color _csbc = csbc != null ? csbc : nimbus_csbc;
        final Color _csfc = csfc != null ? csfc : nimbus_csfc;
        this.setBackground(isSelected ? _csbc : cbc);
        this.setForeground(isSelected ? _csfc : cfc);
        jLabel1.setBackground(isSelected ? _csbc : cbc);
        jLabel1.setForeground(isSelected ? _csfc : cfc);
        jLabel2.setBackground(isSelected ? _csbc : cbc);
        jLabel2.setForeground(isSelected ? _csfc : cfc);
        final ResultType result = (ResultType)value;
        jLabel1.setText(result.symbol);
        jLabel2.setText(result.name);
        return this;
NewJFrame.java
package javaapplication24;
import java.awt.Container;
import java.awt.Dimension;
import javax.swing.JComboBox;
import javax.swing.JList;
import javax.swing.JScrollBar;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;
import javax.swing.event.PopupMenuEvent;
import javax.swing.event.PopupMenuListener;
import javax.swing.plaf.basic.BasicComboPopup;
* @author yccheok
public class NewJFrame extends javax.swing.JFrame {
    public static class ResultType {
         * The symbol.
        public final String symbol;
         * The name.
        public final String name;
        public ResultType(String symbol, String name) {
            this.symbol = symbol;
            this.name = name;
        @Override
        public String toString() {
            return symbol;
    /** Creates new form NewJFrame */
    public NewJFrame() {
        initComponents();
        this.jComboBox1.addPopupMenuListener(this.getPopupMenuListener());
        this.jComboBox1.setRenderer(new ResultSetCellRenderer());
        this.jComboBox1.addItem(new ResultType("Number 1", "Normal"));
        this.jComboBox1.addItem(new ResultType("Number 2", "Normal"));
        this.jComboBox1.addItem(new ResultType("Number 3", "A VERY VERY VERY VERY long text"));
    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">
    private void initComponents() {
        jComboBox1 = new javax.swing.JComboBox();
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        getContentPane().setLayout(new org.netbeans.lib.awtextra.AbsoluteLayout());
        jComboBox1.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jComboBox1ActionPerformed(evt);
        getContentPane().add(jComboBox1, new org.netbeans.lib.awtextra.AbsoluteConstraints(10, 10, 110, -1));
        pack();
    }// </editor-fold>
    private void jComboBox1ActionPerformed(java.awt.event.ActionEvent evt) {
        // TODO add your handling code here:
    * @param args the command line arguments
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                final NewJFrame frame = new NewJFrame();
                frame.setVisible(true);
    private PopupMenuListener getPopupMenuListener() {
        return new PopupMenuListener() {
            @Override
            public void popupMenuWillBecomeVisible(PopupMenuEvent e) {
                // We will have a much wider drop down list.
                adjustPopupWidth(jComboBox1);
            @Override
            public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {
            @Override
            public void popupMenuCanceled(PopupMenuEvent e) {
     * Adjust popup for combo box, so that horizontal scrollbar will not display.
     * Resize JComboBox dropdown doesn't work without customized ListCellRenderer
     * http://www.camick.com/java/source/BoundsPopupMenuListener.java
     * @param comboBox The combo box
    public static void adjustPopupWidth(JComboBox comboBox) {
        if (comboBox.getItemCount() == 0) return;
        Object comp = comboBox.getAccessibleContext().getAccessibleChild(0);
        if (!(comp instanceof BasicComboPopup)) {
            return;
        BasicComboPopup popup = (BasicComboPopup)comp;
        JList list = popup.getList();
        JScrollPane scrollPane = getScrollPane(popup);
        // Just to be paranoid enough.
        if (list == null || scrollPane == null) {
            return;
        //  Determine the maximimum width to use:
        //  a) determine the popup preferred width
        //  b) ensure width is not less than the scroll pane width
        int popupWidth = list.getPreferredSize().width
                        + 5  // make sure horizontal scrollbar doesn't appear
                        + getScrollBarWidth(popup, scrollPane);
        Dimension scrollPaneSize = scrollPane.getPreferredSize();
        popupWidth = Math.max(popupWidth, scrollPaneSize.width);
        //  Adjust the width
        scrollPaneSize.width = popupWidth;
        scrollPane.setPreferredSize(scrollPaneSize);
        scrollPane.setMaximumSize(scrollPaneSize);
     *  I can't find any property on the scrollBar to determine if it will be
     *  displayed or not so use brute force to determine this.
    private static int getScrollBarWidth(BasicComboPopup popup, JScrollPane scrollPane) {
        int scrollBarWidth = 0;
        JComboBox comboBox = (JComboBox)popup.getInvoker();
        if (comboBox.getItemCount() > comboBox.getMaximumRowCount()) {
            JScrollBar vertical = scrollPane.getVerticalScrollBar();
            scrollBarWidth = vertical.getPreferredSize().width;
        return scrollBarWidth;
     *  Get the scroll pane used by the popup so its bounds can be adjusted
    private static JScrollPane getScrollPane(BasicComboPopup popup) {
        JList list = popup.getList();
        Container c = SwingUtilities.getAncestorOfClass(JScrollPane.class, list);
        return (JScrollPane)c;
    // Variables declaration - do not modify
    private javax.swing.JComboBox jComboBox1;
    // End of variables declaration
}Edited by: yccheok on Jan 13, 2011 9:35 AM

Answer 1

Are these two lines intentionally or is it just a mismatch?
jLabel2.setMaximumSize(new java.awt.Dimension(100, 14));
jLabel2.setMinimumSize(new java.awt.Dimension(200, 14));
2) But 1st row and 2nd row cell renderer, do not know 3rd row is holding such a long string.There is only one cell renderer for all rows, so no need for the rows to know each other.
To calculate the exact maximum width of column two, you have to check each entry.
If you can do this BEFORE creating the combo, you could do this in a loop similar to this pseudo code
FontMetrics fm= jComboBox1.getFontMetrics(jComboBox1.getFont());
foreach (column2String) {
  int length= fm.stringWidth(column2String);
  if (length>max) max= length;
}Now you have a max value to dimension jLabel2 in your renderer.
If you don't fill your combo in one go, but rather at runtime, you have to check at each
jComboBox1.addItem(...)
whether the string for label2 is extending the current max, redefine max, and repaint the combo.
This second approach I haven't done so far, but that's how I would try.