This section provides a tutorial example on how to use java.awt.event.ItemListener, radio button and check box item listener interface, to catch state changed item vents on check box menu item objects.
Like JRadioButtonMenuItem, JCheckBoxMenuItem class is a special menu item class,
it supports another event listener, ItemListenser, which allows you to catch radio button state changed events.
Here is an example program I wrote to test the ItemListener interface on check box menu items:
/**
* JCheckBoxMenuItemListenerTest.java
* Copyright (c) 2009 by Dr. Herong Yang, http://www.herongyang.com/
*/
import java.awt.event.*;
import javax.swing.*;
public class JCheckBoxMenuItemListenerTest {
JFrame myFrame = null;
public static void main(String[] a) {
(new JCheckBoxMenuItemListenerTest()).test();
}
private void test() {
myFrame = new JFrame("Menu Listener Test");
myFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
myFrame.setBounds(50,50,250,150);
myFrame.setContentPane(new JDesktopPane());
JMenuBar myMenuBar = new JMenuBar();
JMenu myMenu = getFileMenu();
myMenuBar.add(myMenu);
myMenu = getOptionMenu();
myMenuBar.add(myMenu);
MyMenuItem myItem = new MyMenuItem("Help");
myMenuBar.add(myItem);
myFrame.setJMenuBar(myMenuBar);
myFrame.setVisible(true);
}
private JMenu getFileMenu() {
JMenu myMenu = new JMenu("File");
MyMenuItem myItem = new MyMenuItem("Open");
myMenu.add(myItem);
myItem = new MyMenuItem("Close");
myMenu.add(myItem);
myMenu.addSeparator();
myItem = new MyMenuItem("Exit");
myMenu.add(myItem);
return myMenu;
}
private JMenu getOptionMenu() {
JMenu myMenu = new JMenu("Option");
JCheckBoxMenuItem myItem = new MyCheckBoxMenuItem("Sound");
myItem.setSelected(true);
myMenu.add(myItem);
myItem = new MyCheckBoxMenuItem("Auto save");
myMenu.add(myItem);
return myMenu;
}
private class MyMenuItem extends JMenuItem
implements ActionListener {
public MyMenuItem(String text) {
super(text);
addActionListener(this);
}
public void actionPerformed(ActionEvent e) {
System.out.println("Item clicked: "+e.getActionCommand());
}
}
private class MyCheckBoxMenuItem extends JCheckBoxMenuItem
implements ActionListener, ItemListener {
public MyCheckBoxMenuItem(String text) {
super(text);
addActionListener(this);
addItemListener(this);
}
public void actionPerformed(ActionEvent e) {
System.out.println("Item clicked: "+e.getActionCommand());
}
public void itemStateChanged(ItemEvent e) {
System.out.println("State changed: "+e.getStateChange()
+" on "+((MyCheckBoxMenuItem) e.getItem()).getText());
}
}
}
If you run this example, you will see the frame window shows up with the menu bar like this:
If you click the "Help" menu item and click menu items in the "Option" menu,
you will see some messages printed on the Java console window:
State changed: 1 on Sound
Item clicked: Help
State changed: 1 on Auto save
Item clicked: Auto save
State changed: 2 on Sound
Item clicked: Sound
State changed: 2 on Auto save
Item clicked: Auto save
State changed: 1 on Auto save
Item clicked: Auto save
Interesting notes about this tutorial example:
I used inner class MyCheckBoxMenuItem to create check box menu items with both
ActionListener and ItemListener interfaces implemented in the inner class.
"e.getActionCommand()" expression is used to get action command string, the menu item button text in this case.
"e.getStateChange()" expression is used to get state changed signal
Sample programs listed in this section have been tested with JDK 1.6.0.
