/*

 * Copyright 1997-2005 Sun Microsystems, Inc.  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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package javax.swing;

import java.awt.event.*;

import java.util.Vector;

import java.util.Enumeration;

import java.io.Serializable;

/**

 * This class is used to create a multiple-exclusion scope for

 * a set of buttons. Creating a set of buttons with the

 * same <code>ButtonGroup</code> object means that

 * turning "on" one of those buttons

 * turns off all other buttons in the group.

 * <p>

 * A <code>ButtonGroup</code> can be used with

 * any set of objects that inherit from <code>AbstractButton</code>.

 * Typically a button group contains instances of

 * <code>JRadioButton</code>,

 * <code>JRadioButtonMenuItem</code>,

 * or <code>JToggleButton</code>.

 * It wouldn't make sense to put an instance of

 * <code>JButton</code> or <code>JMenuItem</code>

 * in a button group

 * because <code>JButton</code> and <code>JMenuItem</code>

 * don't implement the selected state.

 * <p>

 * Initially, all buttons in the group are unselected.

 * <p>

 * For examples and further information on using button groups see

 * <a href="http://java.sun.com/docs/books/tutorial/uiswing/components/button.html#radiobutton">How to Use Radio Buttons</a>,

 * a section in <em>The Java Tutorial</em>.

 * <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}.

 *

 * @author Jeff Dinkins

 */

public class ButtonGroup implements Serializable {

    // the list of buttons participating in this group

    protected Vector<AbstractButton> buttons = new Vector();

    /**

     * The current selection.

     */

    ButtonModel selection = null;

    /**

     * Creates a new <code>ButtonGroup</code>.

     */

    public ButtonGroup() {}

    /**

     * Adds the button to the group.

     * @param b the button to be added

     */

    public void add(AbstractButton b) {

        if(b == null) {

            return;

        }

        buttons.addElement(b);

        if (b.isSelected()) {

            if (selection == null) {

                selection = b.getModel();

            } else {

                b.setSelected(false);

            }

        }

        b.getModel().setGroup(this);

    }

    /**

     * Removes the button from the group.

     * @param b the button to be removed

     */

    public void remove(AbstractButton b) {

        if(b == null) {

            return;

        }

        buttons.removeElement(b);

        if(b.getModel() == selection) {

            selection = null;

        }

        b.getModel().setGroup(null);

    }

    /**

     * Clears the selection such that none of the buttons

     * in the <code>ButtonGroup</code> are selected.

     *

     * @since 1.6

     */

    public void clearSelection() {

        if (selection != null) {

            ButtonModel oldSelection = selection;

            selection = null;

            oldSelection.setSelected(false);

        }

    }

    /**

     * Returns all the buttons that are participating in

     * this group.

     * @return an <code>Enumeration</code> of the buttons in this group

     */

    public Enumeration<AbstractButton> getElements() {

        return buttons.elements();

    }

    /**

     * Returns the model of the selected button.

     * @return the selected button model

     */

    public ButtonModel getSelection() {

        return selection;

    }

    /**

     * Sets the selected value for the <code>ButtonModel</code>.

     * Only one button in the group may be selected at a time.

     * @param m the <code>ButtonModel</code>

     * @param b <code>true</code> if this button is to be

     *   selected, otherwise <code>false</code>

     */

    public void setSelected(ButtonModel m, boolean b) {

        if (b && m != null && m != selection) {

            ButtonModel oldSelection = selection;

            selection = m;

            if (oldSelection != null) {

                oldSelection.setSelected(false);

            }

            m.setSelected(true);

        }

    }

    /**

     * Returns whether a <code>ButtonModel</code> is selected.

     * @return <code>true</code> if the button is selected,

     *   otherwise returns <code>false</code>

     */

    public boolean isSelected(ButtonModel m) {

        return (m == selection);

    }

    /**

     * Returns the number of buttons in the group.

     * @return the button count

     * @since 1.3

     */

    public int getButtonCount() {

        if (buttons == null) {

            return 0;

        } else {

            return buttons.size();

        }

    }

}