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java.lang.Object | +--com.ideanest.util.EventListenerList
A class which holds a list of EventListeners. A single instance can be used to hold all listeners (of all types) for the instance using the lsit. It is the responsiblity of the class using the EventListenerList to provide type-safe API (preferably conforming to the JavaBeans spec) and methods which dispatch event notification methods to appropriate Event Listeners on the list. The main benefits which this class provides are that it is relatively cheap in the case of no listeners, and provides serialization for eventlistener lists in a single place, as well as a degree of MT safety (when used correctly). Usage example: Say one is defining a class which sends out FooEvents, and wantds to allow users of the class to register FooListeners and receive notification when FooEvents occur. The following should be added to the class definition:
EventListenerList listenrList = new EventListnerList(); FooEvent fooEvent = null; public void addFooListener(FooListener l) { listenerList.add(FooListener.class, l); } public void removeFooListener(FooListener l) { listenerList.remove(FooListener.class, l); } // Notify all listeners that have registered interest for // notification on this event type. The event instance // is lazily created using the parameters passed into // the fire method. protected void firefooXXX() { // Guaranteed to return a non-null array Object[] listeners = listenerList.getListenerList(); // Process the listeners last to first, notifying // those that are interested in this event for (int i = listeners.length-2; i>=0; i-=2) { if (listeners[i]==FooListener.class) { // Lazily create the event: if (fooEvent == null) fooEvent = new FooEvent(this); ((FooListener)listeners[i+1]).fooXXX(fooEvent); } } }foo should be changed to the appropriate name, and Method to the appropriate method name (one fire method should exist for each notification method in the FooListener interface).
Constructor Summary | |
EventListenerList()
EventListenerList constructor comment. |
Method Summary | |
void |
add(java.lang.Class t,
java.util.EventListener l)
Add the listener as a listener of the specified type. |
int |
getListenerCount()
Return the total number of listeners for this listenerlist |
int |
getListenerCount(java.lang.Class t)
Return the total number of listeners of the supplied type for this listenerlist. |
java.lang.Object[] |
getListenerList()
This passes back the event listener list as an array of ListenerType - listener pairs. |
void |
remove(java.lang.Class t,
java.util.EventListener l)
Remove the listener as a listener of the specified type. |
java.lang.String |
toString()
Return a string representation of the EventListenerList. |
Methods inherited from class java.lang.Object |
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Constructor Detail |
public EventListenerList()
Method Detail |
public void add(java.lang.Class t, java.util.EventListener l)
t
- the type of the listener to be addedl
- the listener to be addedpublic int getListenerCount()
public int getListenerCount(java.lang.Class t)
public java.lang.Object[] getListenerList()
public void remove(java.lang.Class t, java.util.EventListener l)
t
- the type of the listener to be removedl
- the listener to be removedpublic java.lang.String toString()
toString
in class java.lang.Object
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