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<TITLE>Creating a Custom Event
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<h3>
e333.
Creating a Custom Event</h3>
A new custom event must extends <code>EventObject</code>. Moreover, an event
listener interface must be declared to allow objects to receive the
new custom event. All listeners must extend from <code>EventListener</code>.
<P> This example demonstrates all the steps necessary to create a
new custom event.
<pre>
// 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);
}
}
}
}
</pre>
Here's an example of how to register for MyEvents.
<pre>
MyClass c = new MyClass();
// Register for MyEvents from c
c.addMyEventListener(new MyEventListener() {
public void myEventOccurred(MyEvent evt) {
// MyEvent was fired
}
});
</pre>
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Related Examples
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e331. <a class="eglink" href="GenRandom.html?l=rel">
Generating a Random Number
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e332. <a class="eglink" href="ParseString.html?l=rel">
Breaking a String into Words
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e334. <a class="eglink" href="Obs.html?l=rel">
Implementing a Simple Event Notifier
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e335. <a class="eglink" href="GetAllLocales.html?l=rel">
Listing All Available Locales
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e336. <a class="eglink" href="SetDefLocale.html?l=rel">
Setting the Default Locale
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e337. <a class="eglink" href="ValueOnObj.html?l=rel">
Associating a Value with an Object
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See also:
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Arrays">
Arrays
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Bits">
Bits
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Collections">
Collections
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Dates">
Dates
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Hash%20Tables">
Hash Tables
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Lists">
Lists
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Property%20Files">
Property Files
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Sets">
Sets
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Sorted%20Collections">
Sorted Collections
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Time">
Time
</a>
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Timers">
Timers
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