001/*
002 * This library is part of OpenCms -
003 * the Open Source Content Management System
004 *
005 * Copyright (c) Alkacon Software GmbH & Co. KG (http://www.alkacon.com)
006 *
007 * This library is free software; you can redistribute it and/or
008 * modify it under the terms of the GNU Lesser General Public
009 * License as published by the Free Software Foundation; either
010 * version 2.1 of the License, or (at your option) any later version.
011 *
012 * This library is distributed in the hope that it will be useful,
013 * but WITHOUT ANY WARRANTY; without even the implied warranty of
014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
015 * Lesser General Public License for more details.
016 *
017 * For further information about Alkacon Software, please see the
018 * company website: http://www.alkacon.com
019 *
020 * For further information about OpenCms, please see the
021 * project website: http://www.opencms.org
022 *
023 * You should have received a copy of the GNU Lesser General Public
024 * License along with this library; if not, write to the Free Software
025 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
026 */
027
028package org.opencms.gwt.client.util;
029
030/**
031 * Container which contains at most one {@link org.opencms.gwt.client.util.I_CmsUniqueActiveItem}.<p>
032 *
033 * If a new value is set while this container already contains an item, the previous item is removed and notified of that removal.<p>
034 */
035public class CmsUniqueActiveItemContainer {
036
037    /** The current item. */
038    private I_CmsUniqueActiveItem m_activeItem;
039
040    /**
041     * Removes the current item.
042     */
043    public void clear() {
044
045        if (m_activeItem != null) {
046            m_activeItem.onDeactivate();
047            m_activeItem = null;
048        }
049    }
050
051    /**
052     * Removes the current item only if it is the same object as the given parameter.<p>
053     *
054     * @param item the item to match
055     */
056    public void clearIfMatches(I_CmsUniqueActiveItem item) {
057
058        if (item == m_activeItem) {
059            clear();
060        }
061    }
062
063    /**
064     * Sets the active item.<p>
065     *
066     * If this container already contains an item, it is replaced with the given item, and its onDeactivate() method is called.<p>
067     *
068     * @param item the new item
069     */
070    public void setActiveItem(I_CmsUniqueActiveItem item) {
071
072        clear();
073        if (item != null) {
074            m_activeItem = item;
075        }
076    }
077
078}