001/* ===========================================================
002 * JFreeChart : a free chart library for the Java(tm) platform
003 * ===========================================================
004 *
005 * (C) Copyright 2000-2020, 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 * [Oracle and Java are registered trademarks of Oracle and/or its affiliates. 
025 * Other names may be trademarks of their respective owners.]
026 *
027 * --------------------
028 * AbstractOverlay.java
029 * --------------------
030 * (C) Copyright 2009-2020, by Object Refinery Limited.
031 *
032 * Original Author:  David Gilbert (for Object Refinery Limited);
033 * Contributor(s):   -;
034 *
035 */
036
037package org.jfree.chart.panel;
038
039import javax.swing.event.EventListenerList;
040import org.jfree.chart.ChartPanel;
041import org.jfree.chart.event.ChartChangeEvent;
042import org.jfree.chart.event.OverlayChangeEvent;
043import org.jfree.chart.event.OverlayChangeListener;
044import org.jfree.chart.util.Args;
045
046/**
047 * A base class for implementing overlays for a {@link ChartPanel}.
048 *
049 * @since 1.0.13
050 */
051public class AbstractOverlay {
052
053    /** Storage for registered change listeners. */
054    private transient EventListenerList changeListeners;
055
056    /**
057     * Default constructor.
058     */
059    public AbstractOverlay() {
060        this.changeListeners = new EventListenerList();
061    }
062
063    /**
064     * Registers an object for notification of changes to the overlay.
065     *
066     * @param listener  the listener ({@code null} not permitted).
067     *
068     * @see #removeChangeListener(OverlayChangeListener)
069     */
070    public void addChangeListener(OverlayChangeListener listener) {
071        Args.nullNotPermitted(listener, "listener");
072        this.changeListeners.add(OverlayChangeListener.class, listener);
073    }
074
075    /**
076     * Deregisters an object for notification of changes to the overlay.
077     *
078     * @param listener  the listener ({@code null} not permitted)
079     *
080     * @see #addChangeListener(OverlayChangeListener)
081     */
082    public void removeChangeListener(OverlayChangeListener listener) {
083        Args.nullNotPermitted(listener, "listener");
084        this.changeListeners.remove(OverlayChangeListener.class, listener);
085    }
086
087    /**
088     * Sends a default {@link ChartChangeEvent} to all registered listeners.
089     * <P>
090     * This method is for convenience only.
091     */
092    public void fireOverlayChanged() {
093        OverlayChangeEvent event = new OverlayChangeEvent(this);
094        notifyListeners(event);
095    }
096
097    /**
098     * Sends a {@link ChartChangeEvent} to all registered listeners.
099     *
100     * @param event  information about the event that triggered the
101     *               notification.
102     */
103    protected void notifyListeners(OverlayChangeEvent event) {
104       Object[] listeners = this.changeListeners.getListenerList();
105        for (int i = listeners.length - 2; i >= 0; i -= 2) {
106            if (listeners[i] == OverlayChangeListener.class) {
107                ((OverlayChangeListener) listeners[i + 1]).overlayChanged(
108                        event);
109            }
110        }
111    }
112
113}
114