/*
* @(#)EventListenerList.java 1.38 10/03/23
*
* Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package org.jaudiotagger.utils.tree;
import java.io.*;
import java.util.*;
import java.lang.reflect.Array;
/**
* 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:
* <pre>
* 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);
* }
* }
* }
* </pre>
* 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.
* <p>
* <strong>Warning:</strong>
* 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 JavaBeans<sup><font size="-2">TM</font></sup>
* has been added to the <code>java.beans</code> package.
* Please see {@link java.beans.XMLEncoder}.
*
* @version 1.38 03/23/10
* @author Georges Saab
* @author Hans Muller
* @author James Gosling
*/
public class EventListenerList implements Serializable {
/* A null array to be shared by all empty listener lists*/
private final static Object[] NULL_ARRAY = new Object[0];
/* The list of ListenerType - Listener pairs */
protected transient Object[] listenerList = NULL_ARRAY;
/**
* 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.
*/
public Object[] getListenerList() {
return listenerList;
}
/**
* Return an array of all the listeners of the given type.
* @return all of the listeners of the specified type.
* @exception ClassCastException if the supplied class
* is not assignable to EventListener
*
* @since 1.3
*/
public <T extends EventListener> T[] getListeners(Class<T> t) {
Object[] lList = listenerList;
int n = getListenerCount(lList, t);
T[] result = (T[])Array.newInstance(t, n);
int j = 0;
for (int i = lList.length-2; i>=0; i-=2) {
if (lList[i] == t) {
result[j++] = (T)lList[i+1];
}
}
return result;
}
/**
* Returns the total number of listeners for this listener list.
*/
public int getListenerCount() {
return listenerList.length/2;
}
/**
* Returns the total number of listeners of the supplied type
* for this listener list.
*/
public int getListenerCount(Class<?> t) {
Object[] lList = listenerList;
return getListenerCount(lList, t);
}
private int getListenerCount(Object[] list, Class t) {
int count = 0;
for (int i = 0; i < list.length; i+=2) {
if (t == (Class)list[i])
count++;
}
return count;
}
/**
* Adds the listener as a listener of the specified type.
* @param t the type of the listener to be added
* @param l the listener to be added
*/
public synchronized <T extends EventListener> void add(Class<T> t, T l) {
if (l==null) {
// In an ideal world, we would do an assertion here
// to help developers know they are probably doing
// something wrong
return;
}
if (!t.isInstance(l)) {
throw new IllegalArgumentException("Listener " + l +
" is not of type " + t);
}
if (listenerList == NULL_ARRAY) {
// if this is the first listener added,
// initialize the lists
listenerList = new Object[] { t, l };
} else {
// Otherwise copy the array and add the new listener
int i = listenerList.length;
Object[] tmp = new Object[i+2];
System.arraycopy(listenerList, 0, tmp, 0, i);
tmp[i] = t;
tmp[i+1] = l;
listenerList = tmp;
}
}
/**
* Removes the listener as a listener of the specified type.
* @param t the type of the listener to be removed
* @param l the listener to be removed
*/
public synchronized <T extends EventListener> void remove(Class<T> t, T l) {
if (l ==null) {
// In an ideal world, we would do an assertion here
// to help developers know they are probably doing
// something wrong
return;
}
if (!t.isInstance(l)) {
throw new IllegalArgumentException("Listener " + l +
" is not of type " + t);
}
// Is l on the list?
int index = -1;
for (int i = listenerList.length-2; i>=0; i-=2) {
if ((listenerList[i]==t) && (listenerList[i+1].equals(l) == true)) {
index = i;
break;
}
}
// If so, remove it
if (index != -1) {
Object[] tmp = new Object[listenerList.length-2];
// Copy the list up to index
System.arraycopy(listenerList, 0, tmp, 0, index);
// Copy from two past the index, up to
// the end of tmp (which is two elements
// shorter than the old list)
if (index < tmp.length)
System.arraycopy(listenerList, index+2, tmp, index,
tmp.length - index);
// set the listener array to the new array or null
listenerList = (tmp.length == 0) ? NULL_ARRAY : tmp;
}
}
// Serialization support.
private void writeObject(ObjectOutputStream s) throws IOException {
Object[] lList = listenerList;
s.defaultWriteObject();
// Save the non-null event listeners:
for (int i = 0; i < lList.length; i+=2) {
Class t = (Class)lList[i];
EventListener l = (EventListener)lList[i+1];
if ((l!=null) && (l instanceof Serializable)) {
s.writeObject(t.getName());
s.writeObject(l);
}
}
s.writeObject(null);
}
private void readObject(ObjectInputStream s)
throws IOException, ClassNotFoundException {
listenerList = NULL_ARRAY;
s.defaultReadObject();
Object listenerTypeOrNull;
while (null != (listenerTypeOrNull = s.readObject())) {
ClassLoader cl = Thread.currentThread().getContextClassLoader();
EventListener l = (EventListener)s.readObject();
add((Class<EventListener>)Class.forName((String)listenerTypeOrNull, true, cl), l);
}
}
/**
* Returns a string representation of the EventListenerList.
*/
public String toString() {
Object[] lList = listenerList;
String s = "EventListenerList: ";
s += lList.length/2 + " listeners: ";
for (int i = 0 ; i <= lList.length-2 ; i+=2) {
s += " type " + ((Class)lList[i]).getName();
s += " listener " + lList[i+1];
}
return s;
}
}
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