Java SE (Java Platform, Standard Edition)

Previously, I was able to adjusting combo box popup's width, by referring to the technique described in [http://tips4java.wordpress.com/2010/11/28/combo-box-popup/|http://tips4java.wordpress.com/2010/11/28/combo-box-popup/]. During that time, I was using 1.0.6_24-b07.

However, after I update my Java runtime to 1.0.6_26-b03, things broke.

Here is the screen shoot.

[Workable screen shoot|http://i.imgur.com/0elo7.png]
[Not workable screen shoot|http://i.imgur.com/BeKMy.png]

Here is the code snippet to demonstrate this problem.

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/*
 * NewJFrame.java
 *
 * Created on Aug 9, 2011, 4:13:41 AM
 */

package experiment;

import java.awt.Component;
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 {
    /**
     * Adjust popup for combo box, so that horizontal scrollbar will not display.
     * 8039483
     * 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;
        Component component = popup.getInvoker();
        if (component instanceof JComboBox) {
            JComboBox comboBox = (JComboBox)component;

            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;
    }

    /** Creates new form NewJFrame */
    public NewJFrame() {
        initComponents();
        this.jComboBox1.addPopupMenuListener(getPopupMenuListener());
    }

    /** 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);

        jComboBox1.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "Item 1", "Item 2", "Item 3", "Item 4", "This is a very long text. This is a very long text" }));

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(82, 82, 82)
                .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, 76, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(242, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(34, 34, 34)
                .addComponent(jComboBox1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(246, Short.MAX_VALUE))
        );

        pack();
    }// </editor-fold>

    /**
    * @param args the command line arguments
    */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new NewJFrame().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) {
            }
        };
    }

    // Variables declaration - do not modify
    private javax.swing.JComboBox jComboBox1;
    // End of variables declaration

}