JComboBox Input Sources

Question

Hello all,
In regards to the JComboBox, I've made an application that will accept inputs to its value from two different sources / input methods. The first way is the conventional all familiar "click the drop down menu and choose an item in the popup list". The other way would be to edit a value in JTable whose value then modifies the selection shown in the combo box via:
combo.setSelectedIndex(someIndex);When looking at the ActionEvent item produced from the combo change, both methodoligies produce the same "Source" from the following call: (being the JComboBox itself)
public void actionPerformed(ActionEvent e){
    Object source = e.getSource(); //source is the JComboBox         
}I've tried to wrap the events of JComboBox changes into other methods but have run into trouble as the .setSelectedIndex(x) call produces the same ActionEvent as choosing a value from the Combo Box itself. Then subsequently the same code would execute as if the user manually selected the item from the combo box... which is not what I want. I'm wondering if anyone else has encountered this kind of situation and what they've done as a workaround. Is there is a way to determine an input source either from the ActionEvent object or by attaching another type of listerner? Perhaps having an ActionListener on the JComboBox is itself barking up the wrong tree. I could look at the stack trace elements, but that seems a little over the top.
Any thoughts? Thanks
BTW I'm still using 1.5

Answer 1

<snip>
I've tried to wrap the events of JComboBox changes
into other methods but have run into trouble as the
.setSelectedIndex(x) call produces the same
ActionEvent as choosing a value from the Combo Box
itself. Then subsequently the same code would execute
as if the user manually selected the item from the
combo box... which is not what I want.]
I'm wondering
if anyone else has encountered this kind of situation
and what they've done as a workaround. The solution isn't a 'workaround'. The code behaves as it should. If the JComboBox changes, and there is an event listener listening for ActionEvents, the listener should be notified.
To get the behavior you want, you should modify the ActionEvent handler. Use a boolean flag or some other indicator to determine if the event should be ignored. Here's an example using an enum:
import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JTextField;
public class ComboTest {
    private volatile ChangeType changeType = ChangeType.NORMAL;
    ComboTest() {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        final JComboBox cb = new JComboBox();
        for (int i = 0; i < 20; i++) {
            cb.addItem(i);
        cb.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ae) {
                if (changeType == ChangeType.NORMAL) {
                    System.out.println("Selected: " + cb.getSelectedIndex());
        f.add(cb, BorderLayout.NORTH);
        final JTextField tf = new JTextField();
        tf.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent ae) {
                changeType = ChangeType.PROGRAMMATIC;
                cb.setSelectedIndex(Integer.valueOf(tf.getText()));
                changeType = ChangeType.NORMAL;
        f.add(tf, BorderLayout.SOUTH);
        f.setSize(300,200);
        f.setVisible(true);
    public static void main(String[] args) {
        new ComboTest();
    private enum ChangeType {
        NORMAL, PROGRAMMATIC;
}