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 GmbH & Co. KG, 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 030import java.util.HashMap; 031import java.util.Map; 032 033import com.google.gwt.user.client.Command; 034import com.google.gwt.user.client.Timer; 035 036/** 037 * Takes care of the burst of the same event, by skipping the first ones and executing only the last one.<p> 038 * 039 * Usage example: 040 * 041 * <pre> 042 * Window.addResizeHandler(new ResizeHandler() { 043 * public void onResize(ResizeEvent event) { 044 * CmsBurstEventManager.get().schedule("resize-window", new Command() { 045 * public void execute() { 046 * // resize 047 * } 048 * }, 200); 049 * } 050 * }); 051 * </pre> 052 * 053 * @since 8.0.0 054 * 055 * @see <a href="http://ui-programming.blogspot.com/2010/02/gwt-how-to-implement-delayedtask-in.html">Original implementation</a> 056 */ 057public final class CmsBurstEventManager { 058 059 /** 060 * The class is model of one 'burst' event that is added to the manager.<p> 061 */ 062 private static class BurstEvent { 063 064 /** The timer. */ 065 private final Timer m_timer; 066 067 /** 068 * Constructor of the 'burst' event.<p> 069 * 070 * @param name the unique name, which identifies the event 071 * @param command command to execute when the timer expires 072 */ 073 public BurstEvent(final String name, final Command command) { 074 075 m_timer = new Timer() { 076 077 /** 078 * @see com.google.gwt.user.client.Timer#run() 079 */ 080 @Override 081 public void run() { 082 083 if (command != null) { 084 command.execute(); 085 } 086 CmsBurstEventManager.get().cancel(name); 087 } 088 }; 089 } 090 091 /** 092 * Returns the timer.<p> 093 * 094 * @return the timer 095 */ 096 public Timer getTimer() { 097 098 return m_timer; 099 } 100 } 101 102 /** The singleton instance. */ 103 private static CmsBurstEventManager INSTANCE; 104 105 /** The internal memory. */ 106 private Map<String, BurstEvent> m_memory = new HashMap<String, BurstEvent>(); 107 108 /** 109 * Hidden constructor.<p> 110 */ 111 private CmsBurstEventManager() { 112 113 // emtpy 114 } 115 116 /** 117 * Returns the singleton instance.<p> 118 * 119 * @return the singleton instance 120 */ 121 protected static CmsBurstEventManager get() { 122 123 if (INSTANCE == null) { 124 INSTANCE = new CmsBurstEventManager(); 125 } 126 return INSTANCE; 127 } 128 129 /** 130 * Adds an 'burst' event to the manager.<p> 131 * 132 * @param name the unique name, which identifies the event 133 * @param command command to execute when the timer expires 134 * @param delayMsec the timer delay (it's reseted if multiple events are added) 135 */ 136 public void schedule(final String name, final Command command, final int delayMsec) { 137 138 BurstEvent e = m_memory.remove(name); 139 if (e != null) { 140 // disable the old event 141 e.getTimer().cancel(); 142 } 143 // put the new event and schedule it 144 e = new BurstEvent(name, command); 145 m_memory.put(name, e); 146 e.getTimer().schedule(delayMsec); 147 } 148 149 /** 150 * Removes the event from the manager.<p> 151 * 152 * @param eventName the name of the event that we need to remove 153 */ 154 public void cancel(final String eventName) { 155 156 BurstEvent oe = m_memory.remove(eventName); 157 if (oe != null) { 158 // disable the old event. 159 oe.getTimer().cancel(); 160 } 161 } 162}