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Java example source code file (EventListenerList.java)
The EventListenerList.java Java example source code/* * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package javax.swing.event; import java.io.*; import java.util.*; import java.lang.reflect.Array; import sun.reflect.misc.ReflectUtil; /** * 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: * 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™ * has been added to the <code>java.beans package. * Please see {@link java.beans.XMLEncoder}. * * @author Georges Saab * @author Hans Muller * @author James Gosling */ @SuppressWarnings("serial") 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 Other Java examples (source code examples)Here is a short list of links related to this Java EventListenerList.java source code file: |
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