Java tutorial
/* * Copyright (c) 1996, 2013, Oracle and/or its affiliates. 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. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.awt.event; import java.awt.AWTEvent; import java.awt.ItemSelectable; /** * A semantic event which indicates that an item was selected or deselected. * This high-level event is generated by an ItemSelectable object (such as a * List) when an item is selected or deselected by the user. * The event is passed to every {@code ItemListener} object which * registered to receive such events using the component's * {@code addItemListener} method. * <P> * The object that implements the {@code ItemListener} interface gets * this {@code ItemEvent} when the event occurs. The listener is * spared the details of processing individual mouse movements and mouse * clicks, and can instead process a "meaningful" (semantic) event like * "item selected" or "item deselected". * <p> * An unspecified behavior will be caused if the {@code id} parameter * of any particular {@code ItemEvent} instance is not * in the range from {@code ITEM_FIRST} to {@code ITEM_LAST}. * <p> * The {@code stateChange} of any {@code ItemEvent} instance takes one of the following * values: * <ul> * <li> {@code ItemEvent.SELECTED} * <li> {@code ItemEvent.DESELECTED} * </ul> * Assigning the value different from listed above will cause an unspecified behavior. * * @author Carl Quinn * * @see java.awt.ItemSelectable * @see ItemListener * @see <a href="https://docs.oracle.com/javase/tutorial/uiswing/events/itemlistener.html">Tutorial: Writing an Item Listener</a> * * @since 1.1 */ public class ItemEvent extends AWTEvent { /** * The first number in the range of ids used for item events. */ public static final int ITEM_FIRST = 701; /** * The last number in the range of ids used for item events. */ public static final int ITEM_LAST = 701; /** * This event id indicates that an item's state changed. */ public static final int ITEM_STATE_CHANGED = ITEM_FIRST; //Event.LIST_SELECT /** * This state-change value indicates that an item was selected. */ public static final int SELECTED = 1; /** * This state-change-value indicates that a selected item was deselected. */ public static final int DESELECTED = 2; /** * The item whose selection state has changed. * * @serial * @see #getItem() */ Object item; /** * {@code stateChange} indicates whether the {@code item} * was selected or deselected. * * @serial * @see #getStateChange() */ int stateChange; /* * JDK 1.1 serialVersionUID */ private static final long serialVersionUID = -608708132447206933L; /** * Constructs an {@code ItemEvent} object. * <p> This method throws an * {@code IllegalArgumentException} if {@code source} * is {@code null}. * * @param source The {@code ItemSelectable} object * that originated the event * @param id The integer that identifies the event type. * For information on allowable values, see * the class description for {@link ItemEvent} * @param item An object -- the item affected by the event * @param stateChange An integer that indicates whether the item was * selected or deselected. * For information on allowable values, see * the class description for {@link ItemEvent} * @throws IllegalArgumentException if {@code source} is null * @see #getItemSelectable() * @see #getID() * @see #getStateChange() */ public ItemEvent(ItemSelectable source, int id, Object item, int stateChange) { super(source, id); this.item = item; this.stateChange = stateChange; } /** * Returns the originator of the event. * * @return the ItemSelectable object that originated the event. */ public ItemSelectable getItemSelectable() { return (ItemSelectable) source; } /** * Returns the item affected by the event. * * @return the item (object) that was affected by the event */ public Object getItem() { return item; } /** * Returns the type of state change (selected or deselected). * * @return an integer that indicates whether the item was selected * or deselected * * @see #SELECTED * @see #DESELECTED */ public int getStateChange() { return stateChange; } /** * Returns a parameter string identifying this item event. * This method is useful for event-logging and for debugging. * * @return a string identifying the event and its attributes */ public String paramString() { String typeStr; switch (id) { case ITEM_STATE_CHANGED: typeStr = "ITEM_STATE_CHANGED"; break; default: typeStr = "unknown type"; } String stateStr; switch (stateChange) { case SELECTED: stateStr = "SELECTED"; break; case DESELECTED: stateStr = "DESELECTED"; break; default: stateStr = "unknown type"; } return typeStr + ",item=" + item + ",stateChange=" + stateStr; } }