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 listensers: ActionListener, ChangeListener, and ItemListener. The following sample program shows you when those listeners are called, and how many times:

/* JCheckBoxTest.java
 * Copyright (c) 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":

JCheckBox Listeners
JCheckBox Listeners

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 mourse 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:



 

Table of Contents

 About This Book

 JDK (Java Development Kit)

 Introduction of Java Swing Package

 Graphics Environment of the Local System

 JFrame - Main Frame Class

 JLabel - Swing Label Class

 JButton - Swing Button Class

JCheckBox - Swing Check Box Class

 javax.swing.JCheckBox and Related Methods

ActionListener, ChangeListener and ItemListener

 isSelected() - Getting State of Check Box

 JRadioButton - Swing Radio Button Class

 JTextField - Swing Text Field Class

 JComboBox - Swing Combo Box Class

 Menu Bar, Menus, Menu Items and Listeners

 Creating Internal Frames inside the Main Frame

 Layout of Components in a Container

 LookAndFeel and UIManager

 Option Dialog Boxes

 JEditorPane - The Editor Pane Class

 SwingWorker - The Background Task Worker

 AWT (Abstract Windows Toolkit)

 Integration with Desktop System

 Outdated Tutorials

 References

 Full Version in PDF/EPUB