MandatoryCheckBoxController.java

// BlogBridge -- RSS feed reader, manager, and web based service
// Copyright (C) 2002-2006 by R. Pito Salas
//
// This program is free software; you can redistribute it and/or modify it under
// the terms of the GNU General Public License as published by the Free Software Foundation;
// either version 2 of the License, or (at your option) any later version.
//
// This program 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 for more details.
//
// You should have received a copy of the GNU General Public License along with this program;
// if not, write to the Free Software Foundation, Inc., 59 Temple Place,
// Suite 330, Boston, MA 02111-1307 USA
//
// Contact: R. Pito Salas
// mailto:pitosalas@users.sourceforge.net
// More information: about BlogBridge
// http://www.blogbridge.com
// http://sourceforge.net/projects/blogbridge
//
// $Id: MandatoryCheckBoxController.java,v 1.2 2006/01/08 05:07:31 kyank Exp $
//

package com.salas.bb.utils.uif;

import javax.swing.event.ChangeListener;
import javax.swing.event.ChangeEvent;
import javax.swing.*;

/**
 * Helper class to ensure that at least one checkmark is selected.
 */
public class MandatoryCheckBoxController implements ChangeListener
{
    private final JCheckBox box1;
    private final JCheckBox box2;

    /**
     * Creates superviser for two boxes.
     *
     * @param aBox1 first box.
     * @param aBox2 second box.
     */
    public MandatoryCheckBoxController(JCheckBox aBox1, JCheckBox aBox2)
    {
        box1 = aBox1;
        box2 = aBox2;

        box1.addChangeListener(this);
        box2.addChangeListener(this);
    }

    /**
     * Invoked when the state of one of the boxes has changed.
     *
     * @param e event object.
     */
    public void stateChanged(ChangeEvent e)
    {
        JCheckBox box = (JCheckBox)e.getSource();
        if (!box.isSelected()) theOtherBox(box).setSelected(true);
    }

    /**
     * Returns the other box.
     *
     * @param aBox this box.
     *
     * @return the other box.
     */
    private JCheckBox theOtherBox(JCheckBox aBox)
    {
        return aBox == box1 ? box2 : box1;
    }
}