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.
Here's an example of how to register for MyEvents.
// Declare the event. It must extend EventObject.
public class MyEvent extends EventObject {
public MyEvent(Object source) {
super(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) {
((MyEventListener)listeners[i+1]).myEventOccurred(evt);
}
}
}
}
MyClass c = new MyClass();
// Register for MyEvents from c
c.addMyEventListener(new MyEventListener() {
public void myEventOccurred(MyEvent evt) {
// MyEvent was fired
}
});
Thanks.
Excellent example, thank you so much!
I only suggest you to correct the comment on the MyEventListener interface, reflecting the fact that is indeed an interface and not a class.