Java tutorial
/* * Copyright (c) 1997, 2015, 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; import javax.swing.event.*; import java.io.Serializable; import java.util.EventListener; /** * A generic implementation of SingleSelectionModel. * <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™ * has been added to the <code>java.beans</code> package. * Please see {@link java.beans.XMLEncoder}. * * @author Dave Moore * @since 1.2 */ @SuppressWarnings("serial") // Same-version serialization only public class DefaultSingleSelectionModel implements SingleSelectionModel, Serializable { /** * Only one ModelChangeEvent is needed per model instance since the * event's only (read-only) state is the source property. The source * of events generated here is always "this". */ protected transient ChangeEvent changeEvent = null; /** The collection of registered listeners */ protected EventListenerList listenerList = new EventListenerList(); private int index = -1; /** * {@inheritDoc} */ public int getSelectedIndex() { return index; } /** * {@inheritDoc} */ public void setSelectedIndex(int index) { if (this.index != index) { this.index = index; fireStateChanged(); } } /** * {@inheritDoc} */ public void clearSelection() { setSelectedIndex(-1); } /** * {@inheritDoc} */ public boolean isSelected() { boolean ret = false; if (getSelectedIndex() != -1) { ret = true; } return ret; } /** * Adds a <code>ChangeListener</code> to the button. */ public void addChangeListener(ChangeListener l) { listenerList.add(ChangeListener.class, l); } /** * Removes a <code>ChangeListener</code> from the button. */ public void removeChangeListener(ChangeListener l) { listenerList.remove(ChangeListener.class, l); } /** * Returns an array of all the change listeners * registered on this <code>DefaultSingleSelectionModel</code>. * * @return all of this model's <code>ChangeListener</code>s * or an empty * array if no change listeners are currently registered * * @see #addChangeListener * @see #removeChangeListener * * @since 1.4 */ public ChangeListener[] getChangeListeners() { return listenerList.getListeners(ChangeListener.class); } /** * Notifies all listeners that have registered interest for * notification on this event type. The event instance * is created lazily. * @see EventListenerList */ protected void fireStateChanged() { // 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] == ChangeListener.class) { // Lazily create the event: if (changeEvent == null) changeEvent = new ChangeEvent(this); ((ChangeListener) listeners[i + 1]).stateChanged(changeEvent); } } } /** * Returns an array of all the objects currently registered as * <code><em>Foo</em>Listener</code>s * upon this model. * <code><em>Foo</em>Listener</code>s * are registered using the <code>add<em>Foo</em>Listener</code> method. * <p> * You can specify the <code>listenerType</code> argument * with a class literal, such as <code><em>Foo</em>Listener.class</code>. * For example, you can query a <code>DefaultSingleSelectionModel</code> * instance <code>m</code> * for its change listeners * with the following code: * * <pre>ChangeListener[] cls = (ChangeListener[])(m.getListeners(ChangeListener.class));</pre> * * If no such listeners exist, * this method returns an empty array. * * @param <T> the type of {@code EventListener} class being requested * @param listenerType the type of listeners requested; * this parameter should specify an interface * that descends from <code>java.util.EventListener</code> * @return an array of all objects registered as * <code><em>Foo</em>Listener</code>s * on this model, * or an empty array if no such * listeners have been added * @exception ClassCastException if <code>listenerType</code> doesn't * specify a class or interface that implements * <code>java.util.EventListener</code> * * @see #getChangeListeners * * @since 1.3 */ public <T extends EventListener> T[] getListeners(Class<T> listenerType) { return listenerList.getListeners(listenerType); } }