Name: skT88420 Date: 12/09/99


java version "1.2.2"
Classic VM (build JDK-1.2.2-W, native threads, symcjit)

I have a JComboBox which for which I need to monitor for selection/deselection
status. When a selection changes, I wish to see one event for the change, not
individual events for the deselection of one item and the selection of another.
Therfore, I would like to use an ActionEventListener for the JComboBox rather
than an ItemEventListener.

When I add an action listener, I get an event each time the selection changes
(as expected). When I deselect programatically (by doing a setSelectedIndex(-1),
for example), I get a single action event, also as expected.

The problem is when I deselect via the GUI component. If I deselect by
a) clicking the JComboBox to expose its pulldown list, and
b) clicking on a selection from the pulldown list while holding down CTRL
In this case I appear to get 2 action events that appear to contain the same
information.

It doesn't seem to me that JComboBox should be firing multiple action events in
this case...

A sample source file:

=======

import javax.swing.*;
import java.awt.event.*;
public class DeselectionTest extends JFrame
{
  public DeselectionTest()
  {
    super("Combo Box Deselection Test");
    String[] items = {"One", "Two", "Three", "Four"};
    JComboBox box = new JComboBox(items);
    box.addActionListener(new SelectionListener());
    getContentPane().add(box);
  }


  public static void main(String[] args)
  {
    DeselectionTest test = new DeselectionTest();
    test.pack();
    test.setVisible(true);
  }

  private class SelectionListener implements ActionListener
  {
    public void actionPerformed(ActionEvent anEvent)
    {
      System.out.println("Received action event: " + anEvent.toString());
    }
  }
}
(Review ID: 98803)
======================================================================

Name: krT82822 Date: 12/30/99


C:\jdk1.2.2>java -version
java version "1.2"
Classic VM (build JDK-1.2-V, native threads)


The JComboBox will fire two ActionPerformed Events instead of just one after
changing the current selection in the combobox dropdown list. This situation
will occur under these situations:
- Motif PLAF is used
       AND
- selection change is done using the mouse

This situation does not occur if:
- Windows or Java (Metal) PLAF is used
       OR
- selection change is done using the up or down arrow keys on keyboard

Here is code that can be used to demostrate the problem.

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

public class JComboTest extends JPanel {
    JComboBox jComboBox1 = new JComboBox();
    JButton btnMetal = new JButton();
    JButton btnWindows = new JButton();
    JButton btnMotif = new JButton();
    JScrollPane jScrollPane1 = new JScrollPane();
    JList jList1 = new JList(new DefaultListModel());
    JButton btnClear = new JButton();

    public JComboTest() {
        try {
            jbInit();
        }
        catch(Exception ex) {
            ex.printStackTrace();
        }
    }

    private void jbInit() throws Exception {
        this.setLayout(null);
        jComboBox1.setEditable(true);
        jComboBox1.setBounds(new Rectangle(10, 63, 267, 25));
        String item = "Item at ";
        for (int i = 0; i < 11; i ++){
            jComboBox1.addItem (item + i);
        }
        jComboBox1.addActionListener(new java.awt.event.ActionListener() {

            public void actionPerformed(ActionEvent e) {
                jComboBox1_actionPerformed(e);
            }
        });
        btnMetal.setText("Metal");
        btnMetal.setBounds(new Rectangle(300, 15, 87, 23));
        btnMetal.addActionListener(new java.awt.event.ActionListener() {

            public void actionPerformed(ActionEvent e) {
                btnMetal_actionPerformed(e);
            }
        });
        btnWindows.setText("Windows");
        btnWindows.setBounds(new Rectangle(300, 44, 88, 23));
        btnWindows.addActionListener(new java.awt.event.ActionListener() {

            public void actionPerformed(ActionEvent e) {
                btnWindows_actionPerformed(e);
            }
        });
        btnMotif.setText("Motif");
        btnMotif.setBounds(new Rectangle(301, 71, 88, 21));
        btnMotif.addActionListener(new java.awt.event.ActionListener() {

            public void actionPerformed(ActionEvent e) {
                btnMotif_actionPerformed(e);
            }
        });
        jScrollPane1.setBounds(new Rectangle(301, 116, 221, 164));
        btnClear.setText("Clear List");
        btnClear.setBounds(new Rectangle(414, 70, 89, 22));
        btnClear.addActionListener(new java.awt.event.ActionListener() {

            public void actionPerformed(ActionEvent e) {
                btnClear_actionPerformed(e);
            }
        });
        this.add(jComboBox1, null);
        this.add(btnMetal, null);
        this.add(btnWindows, null);
        this.add(btnMotif, null);
        this.add(jScrollPane1, null);
        this.add(btnClear, null);
        jScrollPane1.getViewport().add(jList1, null);

    }

    public static void main (String args[]){
    try{
     UIManager.setLookAndFeel
("com.sun.java.swing.plaf.motif.MotifLookAndFeel");
    }catch(Exception e){
            System.out.println("UIManager exception" + e.toString ());
        }
        javax.swing.JFrame frame = new javax.swing.JFrame();
        JComboTest panel = new JComboTest();
        frame.getContentPane().add(panel);
        frame.setSize(550,300);
        frame.setVisible(true);
        frame.addWindowListener(new java.awt.event.WindowAdapter() {
            public void windowClosing(java.awt.event.WindowEvent we) {
System.exit(0); }
        });
    }

    void jComboBox1_actionPerformed(ActionEvent e) {
        DefaultListModel listModel = (DefaultListModel)jList1.getModel ();
        listModel.addElement("JCombo1 action performed occured");
    }

    void btnMetal_actionPerformed(ActionEvent e) {
        try{
            UIManager.setLookAndFeel
("javax.swing.plaf.metal.MetalLookAndFeel");
            SwingUtilities.updateComponentTreeUI (this);
        }
        catch (Exception e1){
            System.out.println(e1.toString ());
        }
    }

    void btnMotif_actionPerformed(ActionEvent e) {
        try{
            UIManager.setLookAndFeel
("com.sun.java.swing.plaf.motif.MotifLookAndFeel");
            SwingUtilities.updateComponentTreeUI (this);
        }
        catch (Exception e2){
            System.out.println(e2.toString ());
        }
    }

    void btnWindows_actionPerformed(ActionEvent e) {
        try{
            UIManager.setLookAndFeel
("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");
            SwingUtilities.updateComponentTreeUI (this);
        }
        catch (Exception e1){
            System.out.println(e1.toString ());
        }
    }

    void btnClear_actionPerformed(ActionEvent e) {
        DefaultListModel lm = (DefaultListModel)jList1.getModel();
        lm.clear ();
    }
}
(Review ID: 99447)
======================================================================