JDK-4323107 : JList: two ListSelection events if using mouse (one if via keybd navigation)
  • Type: Bug
  • Component: client-libs
  • Sub-Component: javax.swing
  • Affected Version: 1.2.1,1.3.0
  • Priority: P3
  • Status: Closed
  • Resolution: Not an Issue
  • OS: windows_98,windows_nt
  • CPU: x86
  • Submitted: 2000-03-19
  • Updated: 2001-07-12
  • Resolved: 2001-07-12
Description

Name: krT82822			Date: 03/18/2000


/*
1.3.0rc2-W
(see also 4298197 -- and 4134544 <<<--- )
orig. synopsis:  "Clicking on a line in a JList with the mouse gives double events"

Selecting a line in a JList using the mouse gives duplicate events, whereas
moving the cursor with the arrow keys give single events.
In the following, clicking with the mouse on a line (say 'two') results in two
identical lines being printed.
*/

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

public class JListBug102390 extends JFrame {
   
        public JListBug102390() {
        super( "Double selection bug" );
        Container c = getContentPane();
                String[] items = { "one", "two", "three", "four", "five" };
                final JList list = new JList(items);
                list.setSelectionMode(ListSelectionModel.SINGLE_SELECTION);
                c.add(list);

           list.addListSelectionListener(
                new ListSelectionListener() {
                        public void valueChanged (ListSelectionEvent e) {
                                System.out.println(list.getSelectedValue());
                                }
                        }
           );

                pack();
        }

        public static void main(String[] args) {
                JListBug102390 f = new JListBug102390();
                f.setLocation(300,300);
                f.setVisible(true);
        }
}

(Review ID: 102390) 
======================================================================

Comments
WORK AROUND Name: krT82822 Date: 03/18/2000 Monitor the value and check whether it has changed ======================================================================
2004-06-11

EVALUATION We should use property DefaultListSelectionModel.isAdjusting to prevent generation extra list selection events. We should check JList.isValueIsAdjusting() value in JList's internal class ListSelectionHandler.valueChanged() before we fire this event with JList.fireSelectionValueChanged(). ###@###.### 2000-06-05 The first event is sent while the mouse is down to indicate in the process of changing the selection (isAdjusting returns true), the second event is sent when the process has completed (isAdjusting == false). Because the keyboard operation is seen as atomic (we can't tell before hand how many key pressed events we'll see) you only get one event from the keyboard. If this is important to you, you can ignore events that have isAdjusting == true. scott.violet@eng 2001-07-12
2001-07-12

SUGGESTED FIX ------- JList.java ------- *** /tmp/d0WXvIW Mon Jun 5 18:23:49 2000 --- JList.java Mon Jun 5 18:23:14 2000 *************** *** 959,967 **** private class ListSelectionHandler implements ListSelectionListener, Serializable { public void valueChanged(ListSelectionEvent e) { ! fireSelectionValueChanged(e.getFirstIndex(), ! e.getLastIndex(), ! e.getValueIsAdjusting()); } } --- 959,969 ---- private class ListSelectionHandler implements ListSelectionListener, Serializable { public void valueChanged(ListSelectionEvent e) { ! if (!getValueIsAdjusting()) { ! fireSelectionValueChanged(e.getFirstIndex(), ! e.getLastIndex(), ! e.getValueIsAdjusting()); ! } } } ###@###.### 2000-06-05
2000-06-05