/*
 * @(#)DefaultSingleSelectionModel.java	1.32 01/12/03
 *
 * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

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<sup><font size="-2">TM</font></sup>
 * has been added to the <code>java.beans</code> package.
 * Please see {@link java.beans.XMLEncoder}.
 *
 * @version 1.32 12/03/01
 * @author Dave Moore
 */
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;

    // implements javax.swing.SingleSelectionModel
    public int getSelectedIndex() {
        return index;
    }

    // implements javax.swing.SingleSelectionModel
    public void setSelectedIndex(int index) {
        if (this.index != index) {
            this.index = index;
	    fireStateChanged();
        }
    }

    // implements javax.swing.SingleSelectionModel
    public void clearSelection() {
        setSelectedIndex(-1);
    }

    // implements javax.swing.SingleSelectionModel
    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 (ChangeListener[])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 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 EventListener[] getListeners(Class listenerType) { 
	return listenerList.getListeners(listenerType); 
    }
}


