changesupport.java

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/**
 *   ListenerSupport.java
 *   Copyright 2005 Carlos Silva A.
 * 
 *   Licensed under the Apache License, Version 2.0 (the "License");
 *   you may not use this file except in compliance with the License. 
 *   You may obtain a copy of the License at  
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 * 
 */
package jgantt.model;

import java.util.Enumeration;
import java.util.Vector;

/**
 * ListenerSupport, permite Agregar o remover listener a una lista de suscritos.
 * Ademas, permite definir bloques de cambios que deben despacharse 
 * todos juntos al final del bloque.
 * <p>El ultimo mensaje del bloque se envia con la marca:<code>isLast</code>.</p>
 * 
 * <p>$Date: 2004/04/25 03:00:08 $</p> 
 * @version $Revision: 1.2 $
 * @author Carlos Silva
 */
abstract public class ChangeSupport {
	Vector listeners = new Vector();
	boolean dispatchChanges = true;
	Vector eventQueue = new Vector();

	//	metodos publicos
	/**
	 * Agrega un escuchador
	 * @param o listener
	 */
	public void addListener(Object o) {
		if (!listeners.contains(o))
			listeners.addElement(o);
	}
	/**
	 * Elimina un escuchador
	 * @param o listener
	 */
	public void removeListener(Object o) {
		listeners.remove(o);
	}
	
	/**
	 * No envia las notificaciones automaticamente.
	 *
	 */
	public void beginBlockChanges() {
		dispatchChanges = false;
	}
	/**
	 * Envia todos los mensajes pendientes.
	 *
	 */
	public void commitBlockChanges() {
		dispatchChanges = true;
		while (!eventQueue.isEmpty()) {
			Change c = (Change) eventQueue.remove(0);
			if (eventQueue.isEmpty())
				c.setNotLast();
			notifyChange(c);			
		}
	}

	public void sendChange(Change c) {
		if (dispatchChanges) {
			notifyChange(c);
		} else
			eventQueue.add(c);
	}

	// funciones protegidas 
	protected void notifyChange(Change c) {
		for (Enumeration e = listeners.elements(); e.hasMoreElements();) {
			Object l = e.nextElement();
			notifyListener(l, c);
		}
	}
	/**
	 * 
	 * @param listener Objeto a notificar
	 * @param change Cambio que ha sido realizado
	 */
	abstract protected void notifyListener(Object listener, Change change);

}