Creating a Custom Event

Java/Java 2007. 10. 29. 22:26
e333. Creating a Custom Event

A new custom event must extends EventObject. Moreover, an event listener interface must be declared to allow objects to receive the new custom event. All listeners must extend from EventListener.

This example demonstrates all the steps necessary to create a new custom event.

// Declare the event. It must extend EventObject.
public class MyEvent extends EventObject {
    public MyEvent(Object source) {
// Declare the listener class. It must extend EventListener.
// A class must implement this interface to get MyEvents.
public interface MyEventListener extends EventListener {
    public void myEventOccurred(MyEvent evt);
// Add the event registration and notification code to a class.
public class MyClass {
    // Create the listener list
    protected javax.swing.event.EventListenerList listenerList =
        new javax.swing.event.EventListenerList();

    // This methods allows classes to register for MyEvents
    public void addMyEventListener(MyEventListener listener) {
        listenerList.add(MyEventListener.class, listener);
    // This methods allows classes to unregister for MyEvents
    public void removeMyEventListener(MyEventListener listener) {
        listenerList.remove(MyEventListener.class, listener);
    // This private class is used to fire MyEvents
    void fireMyEvent(MyEvent evt) {
        Object[] listeners = listenerList.getListenerList();
        // Each listener occupies two elements - the first is the listener class
        // and the second is the listener instance
        for (int i=0; i<listeners.length; i+=2) {
            if (listeners[i]==MyEventListener.class) {

Here's an example of how to register for MyEvents.
MyClass c = new MyClass();
// Register for MyEvents from c
c.addMyEventListener(new MyEventListener() {
    public void myEventOccurred(MyEvent evt) {
        // MyEvent was fired


Posted by

댓글을 달아 주세요