001/* ===========================================================
002 * JFreeChart : a free chart library for the Java(tm) platform
003 * ===========================================================
004 *
005 * (C) Copyright 2000-2009, by Object Refinery Limited and Contributors.
006 *
007 * Project Info:  http://www.jfree.org/jfreechart/index.html
008 *
009 * This library is free software; you can redistribute it and/or modify it
010 * under the terms of the GNU Lesser General Public License as published by
011 * the Free Software Foundation; either version 2.1 of the License, or
012 * (at your option) any later version.
013 *
014 * This library is distributed in the hope that it will be useful, but
015 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
016 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
017 * License for more details.
018 *
019 * You should have received a copy of the GNU Lesser General Public
020 * License along with this library; if not, write to the Free Software
021 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
022 * USA.
023 *
024 * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
025 * in the United States and other countries.]
026 *
027 * --------------------
028 * AbstractOverlay.java
029 * --------------------
030 * (C) Copyright 2009, by Object Refinery Limited.
031 *
032 * Original Author:  David Gilbert (for Object Refinery Limited);
033 * Contributor(s):   -;
034 *
035 * Changes:
036 * --------
037 * 09-Apr-2009 : Version 1 (DG);
038 *
039 */
040
041package org.jfree.chart.panel;
042
043import javax.swing.event.EventListenerList;
044import org.jfree.chart.ChartPanel;
045import org.jfree.chart.event.ChartChangeEvent;
046import org.jfree.chart.event.OverlayChangeEvent;
047import org.jfree.chart.event.OverlayChangeListener;
048
049/**
050 * A base class for implementing overlays for a {@link ChartPanel}.
051 *
052 * @since 1.0.13
053 */
054public class AbstractOverlay {
055
056    /** Storage for registered change listeners. */
057    private transient EventListenerList changeListeners;
058
059    /**
060     * Default constructor.
061     */
062    public AbstractOverlay() {
063        this.changeListeners = new EventListenerList();
064    }
065
066    /**
067     * Registers an object for notification of changes to the overlay.
068     *
069     * @param listener  the listener (<code>null</code> not permitted).
070     *
071     * @see #removeChangeListener(OverlayChangeListener)
072     */
073    public void addChangeListener(OverlayChangeListener listener) {
074        if (listener == null) {
075            throw new IllegalArgumentException("Null 'listener' argument.");
076        }
077        this.changeListeners.add(OverlayChangeListener.class, listener);
078    }
079
080    /**
081     * Deregisters an object for notification of changes to the overlay.
082     *
083     * @param listener  the listener (<code>null</code> not permitted)
084     *
085     * @see #addChangeListener(OverlayChangeListener)
086     */
087    public void removeChangeListener(OverlayChangeListener listener) {
088        if (listener == null) {
089            throw new IllegalArgumentException("Null 'listener' argument.");
090        }
091        this.changeListeners.remove(OverlayChangeListener.class, listener);
092    }
093
094    /**
095     * Sends a default {@link ChartChangeEvent} to all registered listeners.
096     * <P>
097     * This method is for convenience only.
098     */
099    public void fireOverlayChanged() {
100        OverlayChangeEvent event = new OverlayChangeEvent(this);
101        notifyListeners(event);
102    }
103
104    /**
105     * Sends a {@link ChartChangeEvent} to all registered listeners.
106     *
107     * @param event  information about the event that triggered the
108     *               notification.
109     */
110    protected void notifyListeners(OverlayChangeEvent event) {
111       Object[] listeners = this.changeListeners.getListenerList();
112        for (int i = listeners.length - 2; i >= 0; i -= 2) {
113            if (listeners[i] == OverlayChangeListener.class) {
114                ((OverlayChangeListener) listeners[i + 1]).overlayChanged(
115                        event);
116            }
117        }
118    }
119
120}
121