How to update JComboBox instances in Swing?

Question

I\'ve 3 comboboxes, upon selecting first combobox, the rest should be updated but my code doesn\'t seems to be working. Please help in this guys. Here is my code(since my co

Answer 1

If you intention is to change the combo box values when the user makes a selection, then you are better off using a ActionListener.

If you want to the combo boxes to update each time the user selects a different item in the drop down list (and, yes, this is a different event), then you should use an ItemListener

But in either case, the process is the same...

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.DefaultComboBoxModel;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class ComboBoxUpdates {

    public static void main(String[] args) {
        new ComboBoxUpdates();
    }

    public ComboBoxUpdates() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {

        private JComboBox<String> cb1, cb2, cb3;

        public TestPane() {
            cb1 = new JComboBox<>(new String[]{"Click me", "Click me", "Click them"});
            cb2 = new JComboBox<>();
            cb3 = new JComboBox<>();
            setLayout(new GridBagLayout());
            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;
            add(cb1, gbc);
            add(cb2, gbc);
            add(cb3, gbc);

            cb1.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    cb2.setModel(new DefaultComboBoxModel<String>(new String[]{"item1", "item2", "item3"}));
                    cb3.setModel(new DefaultComboBoxModel<String>(new String[]{"item4", "item5", "item6"}));
                }
            });
        }    
    }
}