javax.swing.event
Class EventListenerList

java.lang.Object sample code for java.lang.Object definition code for java.lang.Object 
  extended by javax.swing.event.EventListenerList
All Implemented Interfaces:
Serializable sample code for java.io.Serializable definition code for java.io.Serializable

public class EventListenerList
extends Object sample code for java.lang.Object definition code for java.lang.Object
implements Serializable sample code for java.io.Serializable definition code for java.io.Serializable

A class that holds a list of EventListeners. A single instance can be used to hold all listeners (of all types) for the instance using the list. 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 that this class provides are that it is relatively cheap in the case of no listeners, and it provides serialization for event-listener lists in a single place, as well as a degree of MT safety (when used correctly). Usage example: Say one is defining a class that sends out FooEvents, and one wants 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 listenerList = new EventListenerList();
 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 fireFooXxx to the appropriate method name. One fire method should exist for each notification method in the FooListener interface.

Warning: Serialized objects of this class will not be compatible with future Swing releases. The current serialization support is appropriate for short term storage or RMI between applications running the same version of Swing. As of 1.4, support for long term storage of all JavaBeansTM has been added to the java.beans package. Please see XMLEncoder sample code for java.beans.XMLEncoder definition code for java.beans.XMLEncoder .

See Also:
Serialized Form

Field Summary
protected  Object sample code for java.lang.Object definition code for java.lang.Object [] listenerList sample code for javax.swing.event.EventListenerList.listenerList definition code for javax.swing.event.EventListenerList.listenerList
           
 
Constructor Summary
EventListenerList sample code for javax.swing.event.EventListenerList.EventListenerList() definition code for javax.swing.event.EventListenerList.EventListenerList() ()
           
 
Method Summary
<T extends EventListener sample code for java.util.EventListener definition code for java.util.EventListener >
void
add sample code for javax.swing.event.EventListenerList.add(java.lang.Class, T) definition code for javax.swing.event.EventListenerList.add(java.lang.Class, T) (Class sample code for java.lang.Class definition code for java.lang.Class <T> t, T l)
          Adds the listener as a listener of the specified type.
 int getListenerCount sample code for javax.swing.event.EventListenerList.getListenerCount() definition code for javax.swing.event.EventListenerList.getListenerCount() ()
          Returns the total number of listeners for this listener list.
 int getListenerCount sample code for javax.swing.event.EventListenerList.getListenerCount(java.lang.Class) definition code for javax.swing.event.EventListenerList.getListenerCount(java.lang.Class) (Class sample code for java.lang.Class definition code for java.lang.Class <?> t)
          Returns the total number of listeners of the supplied type for this listener list.
 Object sample code for java.lang.Object definition code for java.lang.Object [] getListenerList sample code for javax.swing.event.EventListenerList.getListenerList() definition code for javax.swing.event.EventListenerList.getListenerList() ()
          Passes back the event listener list as an array of ListenerType-listener pairs.
<T extends EventListener sample code for java.util.EventListener definition code for java.util.EventListener >
T[]
getListeners sample code for javax.swing.event.EventListenerList.getListeners(java.lang.Class) definition code for javax.swing.event.EventListenerList.getListeners(java.lang.Class) (Class sample code for java.lang.Class definition code for java.lang.Class <T> t)
          Return an array of all the listeners of the given type.
<T extends EventListener sample code for java.util.EventListener definition code for java.util.EventListener >
void
remove sample code for javax.swing.event.EventListenerList.remove(java.lang.Class, T) definition code for javax.swing.event.EventListenerList.remove(java.lang.Class, T) (Class sample code for java.lang.Class definition code for java.lang.Class <T> t, T l)
          Removes the listener as a listener of the specified type.
 String sample code for java.lang.String definition code for java.lang.String toString sample code for javax.swing.event.EventListenerList.toString() definition code for javax.swing.event.EventListenerList.toString() ()
          Returns a string representation of the EventListenerList.
 
Methods inherited from class java.lang.Object sample code for java.lang.Object definition code for java.lang.Object
clone sample code for java.lang.Object.clone() definition code for java.lang.Object.clone() , equals sample code for java.lang.Object.equals(java.lang.Object) definition code for java.lang.Object.equals(java.lang.Object) , finalize sample code for java.lang.Object.finalize() definition code for java.lang.Object.finalize() , getClass sample code for java.lang.Object.getClass() definition code for java.lang.Object.getClass() , hashCode sample code for java.lang.Object.hashCode() definition code for java.lang.Object.hashCode() , notify sample code for java.lang.Object.notify() definition code for java.lang.Object.notify() , notifyAll sample code for java.lang.Object.notifyAll() definition code for java.lang.Object.notifyAll() , wait sample code for java.lang.Object.wait() definition code for java.lang.Object.wait() , wait sample code for java.lang.Object.wait(long) definition code for java.lang.Object.wait(long) , wait sample code for java.lang.Object.wait(long, int) definition code for java.lang.Object.wait(long, int)
 

Field Detail

listenerList sample code for javax.swing.event.EventListenerList.listenerList

protected transient Object sample code for java.lang.Object definition code for java.lang.Object [] listenerList
Constructor Detail

EventListenerList sample code for javax.swing.event.EventListenerList() definition code for javax.swing.event.EventListenerList()

public EventListenerList()
Method Detail

getListenerList sample code for javax.swing.event.EventListenerList.getListenerList() definition code for javax.swing.event.EventListenerList.getListenerList()

public Object sample code for java.lang.Object definition code for java.lang.Object [] getListenerList()
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 listener 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.


getListeners sample code for javax.swing.event.EventListenerList.<T extends java.util.EventListener>getListeners(java.lang.Class<T>) definition code for javax.swing.event.EventListenerList.<T extends java.util.EventListener>getListeners(java.lang.Class<T>)

public <T extends EventListener sample code for java.util.EventListener definition code for java.util.EventListener > T[] getListeners(Class sample code for java.lang.Class definition code for java.lang.Class <T> t)
Return an array of all the listeners of the given type.

Returns:
all of the listeners of the specified type.
Throws:
ClassCastException sample code for java.lang.ClassCastException definition code for java.lang.ClassCastException - if the supplied class is not assignable to EventListener
Since:
1.3

getListenerCount sample code for javax.swing.event.EventListenerList.getListenerCount() definition code for javax.swing.event.EventListenerList.getListenerCount()

public int getListenerCount()
Returns the total number of listeners for this listener list.


getListenerCount sample code for javax.swing.event.EventListenerList.getListenerCount(java.lang.Class<?>) definition code for javax.swing.event.EventListenerList.getListenerCount(java.lang.Class<?>)

public int getListenerCount(Class sample code for java.lang.Class definition code for java.lang.Class <?> t)
Returns the total number of listeners of the supplied type for this listener list.


add sample code for javax.swing.event.EventListenerList.<T extends java.util.EventListener>add(java.lang.Class<T>, T) definition code for javax.swing.event.EventListenerList.<T extends java.util.EventListener>add(java.lang.Class<T>, T)

public <T extends EventListener sample code for java.util.EventListener definition code for java.util.EventListener > void add(Class sample code for java.lang.Class definition code for java.lang.Class <T> t,
                                          T l)
Adds the listener as a listener of the specified type.

Parameters:
t - the type of the listener to be added
l - the listener to be added

remove sample code for javax.swing.event.EventListenerList.<T extends java.util.EventListener>remove(java.lang.Class<T>, T) definition code for javax.swing.event.EventListenerList.<T extends java.util.EventListener>remove(java.lang.Class<T>, T)

public <T extends EventListener sample code for java.util.EventListener definition code for java.util.EventListener > void remove(Class sample code for java.lang.Class definition code for java.lang.Class <T> t,
                                             T l)
Removes the listener as a listener of the specified type.

Parameters:
t - the type of the listener to be removed
l - the listener to be removed

toString sample code for javax.swing.event.EventListenerList.toString() definition code for javax.swing.event.EventListenerList.toString()

public String sample code for java.lang.String definition code for java.lang.String  toString()
Returns a string representation of the EventListenerList.

Overrides:
toString sample code for java.lang.Object.toString() definition code for java.lang.Object.toString() in class Object sample code for java.lang.Object definition code for java.lang.Object
Returns:
a string representation of the object.