ActionListener, ChangeListener and ItemListener

Java Swing Tutorials - Herong's Tutorial Examples

∟ActionListener, ChangeListener and ItemListener

This section provides a tutorial example on how to use ActionListener, ChangeListener and ItemListener interfaces to handle different types of events generated on check boxes.

As you can see from the previous section, a check box can have 3 types of event listeners: ActionListener, ChangeListener, and ItemListener. The following sample program shows you when those listeners are called, and how many times:

/* JCheckBoxTest.java
 * Copyright (c) 1997-2024 HerongYang.com. All Rights Reserved.
 */
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
public class JCheckBoxTest {
   public static void main(String[] a) {
      JFrame f = new JFrame("My Check Boxes");
      f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  
      MyCheckBox red = new MyCheckBox("Red");
      f.getContentPane().add(red,BorderLayout.NORTH);
    
      MyCheckBox green = new MyCheckBox("Green");
      f.getContentPane().add(green,BorderLayout.CENTER);
    
      MyCheckBox blue = new MyCheckBox("Blue");
      f.getContentPane().add(blue,BorderLayout.SOUTH);
    
      f.pack();
      f.setVisible(true);
   }
   private static class MyCheckBox extends JCheckBox 
      implements ActionListener, ChangeListener, ItemListener  {
      static int count = 0;
      String text = null;
      public MyCheckBox(String t) {
         super(t);
         text = t;
         addActionListener(this);
         addChangeListener(this);
         addItemListener(this);
      }
      public void actionPerformed(ActionEvent e) {
         count++;
         System.out.println(count+": Action performed - "+text);
      }
      public void stateChanged(ChangeEvent e) {
         count++;
         System.out.println(count+": State changed - "+text);
      }
      public void itemStateChanged(ItemEvent e) {
         count++;
         System.out.println(count+": Item state changed - "+text);
      }
   }
}

This example program creates 3 check boxes. Each button has 3 listeners to handle 3 different types of events. A counter is used in the listener class to help to identify the order of events.

If you run this program, you will see 3 check boxes: "Red", "Green" and "Blue":

If you move your mouse to the "Red" check box, you see 1 "State changed" message. If you press the "Red" check box, you see 2 more "State changed" messages. If you release the "Red" check box, you see 5 more messages. If you move your mouse away from the "Red" check box, you see 1 more "State changed" message.

1: State changed - Red

2: State changed - Red
3: State changed - Red

4: State changed on - Red
5: Item state changed - Red
6: State changed on - Red
7: Action performed - Red
8: State changed on - Red

9: State changed on - Red

10: State changed on - Green

11: State changed on - Green
12: State changed on - Green

13: State changed on - Green
14: Item state changed - Green
15: State changed on - Green
16: Action performed - Green
17: State changed on - Green

18: State changed on - Green

Note that:

Action event raised only once when you release a check box.
Item event (itemStateChanged method call) is raised only once when you release a check box.
Change event (stateChanged method call) is raised many times, when you move your mouse in to and out of a check box, press and release a check box.