com.ideanest.util
Class EventListenerList
java.lang.Object
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+--com.ideanest.util.EventListenerList
- All Implemented Interfaces:
- java.io.Serializable
- public class EventListenerList
- extends java.lang.Object
- implements java.io.Serializable
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).
- Version:
- 1.22 08/28/98
- Author:
- Piotr Kaminski, Georges Saab, Hans Muller, James Gosling
- See Also:
- Serialized Form
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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 |
EventListenerList
public EventListenerList()
- EventListenerList constructor comment.
add
public void add(java.lang.Class t,
java.util.EventListener l)
- Add the listener as a listener of the specified type.
- Parameters:
t - the type of the listener to be addedl - the listener to be added
getListenerCount
public int getListenerCount()
- Return the total number of listeners for this listenerlist
getListenerCount
public int getListenerCount(java.lang.Class t)
- Return the total number of listeners of the supplied type
for this listenerlist.
getListenerList
public java.lang.Object[] getListenerList()
- This passes back the event listener list as an array
of ListenerType - listener pairs. Note that for
performance reasons, this implementation passes back
the actual data structure in which the listner data
is stored internally!
This method is guaranteed to pass back a non-null
array, so that no null-checking is required in
fire methods. A zero-length array of Object should
be returned if there are currently no listeners.
WARNING!!! Absolutely NO modification of
the data contained in this array should be made -- if
any such manipulation is necessary, it should be done
on a copy of the array returned rather than the array
itself.
remove
public void remove(java.lang.Class t,
java.util.EventListener l)
- Remove the listener as a listener of the specified type.
- Parameters:
t - the type of the listener to be removedl - the listener to be removed
toString
public java.lang.String toString()
- Return a string representation of the EventListenerList.
- Overrides:
toString in class java.lang.Object
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