∟javax.swing.event.MenuListener - Menu Listener Interface
This section provides a tutorial example on how to use javax.swing.event.MenuListener, menu listener interface, to catch events fired by JMenu objects.
Like any other user interface components, JMenu objects fire events when users interact with them.
If you want to perform a task when an event occurs on a JMenu object, you need to add an event listener to that JMenu object.
To do this, you need know these Swing classes, interfaces and methods:
javax.swing.event.MenuListener - A Swing interface that allows you to implement your own menu event handler methods:
menuSelected(MenuEvent) - Event handler method called when the associated menu is selected. You need to implement this method to perform your own task.
menuDeselected(MenuEvent) - Event handler method called when the associated menu is deselected. You need to implement this method to perform your own task.
menuCanceled(MenuEvent) - Event handler method called when the associated menu is canceled. You need to implement this method to perform your own task.
javax.swing.event.MenuEvent - A Swing class that represents an event occurred on a menu. The most important method in this class is:
getSource() - Method returns the JMenu object where the event occurred.
Here is an example program I wrote to test the MenuListener interface:
/**
* MenuListenerTest.java
* Copyright (c) 2009 by Dr. Herong Yang, http://www.herongyang.com/
*/
import javax.swing.*;
import javax.swing.event.*;
public class MenuListenerTest implements MenuListener {
JFrame myFrame = null;
public static void main(String[] a) {
(new MenuListenerTest()).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();
myMenu.addMenuListener(this);
myMenuBar.add(myMenu);
myMenu = getColorMenu();
myMenu.addMenuListener(this);
myMenuBar.add(myMenu);
myMenu = getOptionMenu();
myMenu.addMenuListener(this);
myMenuBar.add(myMenu);
JMenuItem myItem = new JMenuItem("Help");
myMenuBar.add(myItem);
myFrame.setJMenuBar(myMenuBar);
myFrame.setVisible(true);
}
private JMenu getFileMenu() {
JMenu myMenu = new JMenu("File");
JMenuItem myItem = new JMenuItem("Open");
myMenu.add(myItem);
myItem = new JMenuItem("Close");
myMenu.add(myItem);
myMenu.addSeparator();
myItem = new JMenuItem("Exit");
myMenu.add(myItem);
return myMenu;
}
private JMenu getColorMenu() {
JMenu myMenu = new JMenu("Color");
JMenuItem myItem = new JMenuItem("Red");
myMenu.add(myItem);
myItem = new JMenuItem("Green");
myMenu.add(myItem);
myItem = new JMenuItem("Blue");
myMenu.add(myItem);
return myMenu;
}
private JMenu getOptionMenu() {
JMenu myMenu = new JMenu("Option");
JMenuItem myItem = new JMenuItem("Sound");
myMenu.add(myItem);
myItem = new JMenuItem("Auto save");
myMenu.add(myItem);
return myMenu;
}
public void menuSelected(MenuEvent e) {
JMenu myMenu = (JMenu) e.getSource();
System.out.println("Menu Selected: "+myMenu.getText());
}
public void menuDeselected(MenuEvent e) {
JMenu myMenu = (JMenu) e.getSource();
System.out.println("Menu deselected: "+myMenu.getText());
}
public void menuCanceled(MenuEvent e) {
JMenu myMenu = (JMenu) e.getSource();
System.out.println("Menu anceled: "+myMenu.getText());
}
}
If you run this example, you will see the frame window shows up with the menu bar like this:
If you click the "File" menu, move to the "Color" menu, then move to the "Option" menu,
you will see some messages printed on the Java console window:
Menu Selected: File
Menu deselected: File
Menu Selected: Color
Menu deselected: Color
Menu Selected: Option
Interesting notes about this tutorial example:
"public class MenuListenerTest implements MenuListener" declaration is used to make my MenuListenerTest object
becoming a MenuListener object.
"myMenu.addMenuListener(this);" statement is used to add a MenuListener object to a JMenu object.
"JMenu myMenu = (JMenu) e.getSource();" statement is used to get the JMenu object where the event was fired.
"myMenu.getText()" expression is used to get the menu button text.
Sample programs listed in this section have been tested with JDK 1.6.0.
