Alter JComboBox popup size without disturbing Look and Feel?

Question

I\'m looking for a way to alter the width of a JComboBox\'s popup. Basically, the popup should be as wide as the widest combobox entry requires, not as wide as the combobox curr

Answer 1

1. by using GBC you are be able to set proper height and weight in the container

2. as @trashgod mentioned next way is to set for PreferredSize by using JComboBox.setPrototypeDisplayValue()

3. use Combo Box Popup by @camickr

4. for derived JPopup must be used pack() otherwise too hard to change its Dimension easilly

.

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.plaf.basic.*;

public class ComboBoxExample extends JPanel implements ActionListener {
//http://stackoverflow.com/a/5058210/714968

    private static final long serialVersionUID = 1L;
    private JComboBox comboBox;

    public ComboBoxExample() {
        String[] petStrings = {"Select Pet", "Bird", "Cat", "Dog", "Rabbit", "Pig", "Other"};
        comboBox = new JComboBox(petStrings);
        comboBox.setPrototypeDisplayValue("XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX");
        add(comboBox, BorderLayout.PAGE_START);
        JFrame frame = new JFrame("ComboBoxExample");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.add(comboBox);
        frame.setName("ComboBoxExample");
        frame.setLocation(150, 150);
        frame.pack();
        frame.setVisible(true);
        Timer timer = new javax.swing.Timer(2000, this);
        timer.start();
    }

    public void actionPerformed(ActionEvent e) {
        comboBox.showPopup();
        Object child = comboBox.getAccessibleContext().getAccessibleChild(0);
        BasicComboPopup popup = (BasicComboPopup) child;
        popup.setName("BasicComboPopup");
        JList list = popup.getList();
        Container c = SwingUtilities.getAncestorOfClass(JScrollPane.class, list);
        JScrollPane scrollPane = (JScrollPane) c;
        Dimension size = scrollPane.getSize();
        if (size.width > 30) {
            size.width -= 5;
        }
        scrollPane.setPreferredSize(size);
        scrollPane.setMaximumSize(size);
        Dimension popupSize = popup.getSize();
        popupSize.width = size.width;
        Component parent = popup.getParent();
        parent.setSize(popupSize);
        parent.validate();
        parent.repaint();
        Window mainFrame = SwingUtilities.windowForComponent(comboBox);
        //Returns the first Window ancestor of c, or null if c is not contained inside a Window.
        System.out.println(mainFrame.getName());
        Window popupWindow = SwingUtilities.windowForComponent(popup);
        System.out.println(popupWindow.getName());
        Window popupWindowa = SwingUtilities.windowForComponent(c);
        System.out.println(popupWindowa.getName());

        Window mainFrame1 = SwingUtilities.getWindowAncestor(comboBox);
        //Returns the first Window ancestor of c, or null if c is not contained inside a Window.
        System.out.println(mainFrame1.getName());
        Window popupWindow1 = SwingUtilities.getWindowAncestor(popup);
        System.out.println(popupWindow1.getName());

        Component mainFrame2 = SwingUtilities.getRoot(comboBox);
        //Returns the root component for the current component tree.
        System.out.println(mainFrame2.getName());
        Component popupWindow2 = SwingUtilities.getRoot(popup);
        System.out.println(popupWindow2.getName());
        //  For heavy weight popups you need always to pack() for the window
        if (popupWindow != mainFrame) {
            popupWindow.pack();
        }
    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {

            public void run() {
                ComboBoxExample comboBoxExample = new ComboBoxExample();
            }
        });
    }
}