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.Component; import java.awt.Rectangle; import java.lang.annotation.Native; /** * A low-level event which indicates that a component moved, changed * size, or changed visibility (also, the root class for the other * component-level events). * <P> * Component events are provided for notification purposes ONLY; * The AWT will automatically handle component moves and resizes * internally so that GUI layout works properly regardless of * whether a program is receiving these events or not. * <P> * In addition to serving as the base class for other component-related * events (InputEvent, FocusEvent, WindowEvent, ContainerEvent), * this class defines the events that indicate changes in * a component's size, position, or visibility. * <P> * This low-level event is generated by a component object (such as a * List) when the component is moved, resized, rendered invisible, or made * visible again. The event is passed to every {@code ComponentListener} * or {@code ComponentAdapter} object which registered to receive such * events using the component's {@code addComponentListener} method. * ({@code ComponentAdapter} objects implement the * {@code ComponentListener} interface.) Each such listener object * gets this {@code ComponentEvent} when the event occurs. * <p> * An unspecified behavior will be caused if the {@code id} parameter * of any particular {@code ComponentEvent} instance is not * in the range from {@code COMPONENT_FIRST} to {@code COMPONENT_LAST}. * * @see ComponentAdapter * @see ComponentListener * @see <a href="https://docs.oracle.com/javase/tutorial/uiswing/events/componentlistener.html">Tutorial: Writing a Component Listener</a> * * @author Carl Quinn * @since 1.1 */ public class ComponentEvent extends AWTEvent { /** * The first number in the range of ids used for component events. */ public static final int COMPONENT_FIRST = 100; /** * The last number in the range of ids used for component events. */ public static final int COMPONENT_LAST = 103; /** * This event indicates that the component's position changed. */ @Native public static final int COMPONENT_MOVED = COMPONENT_FIRST; /** * This event indicates that the component's size changed. */ @Native public static final int COMPONENT_RESIZED = 1 + COMPONENT_FIRST; /** * This event indicates that the component was made visible. */ @Native public static final int COMPONENT_SHOWN = 2 + COMPONENT_FIRST; /** * This event indicates that the component was rendered invisible. */ @Native public static final int COMPONENT_HIDDEN = 3 + COMPONENT_FIRST; /* * JDK 1.1 serialVersionUID */ private static final long serialVersionUID = 8101406823902992965L; /** * Constructs a {@code ComponentEvent} object. * <p> This method throws an * {@code IllegalArgumentException} if {@code source} * is {@code null}. * * @param source The {@code Component} that originated the event * @param id An integer indicating the type of event. * For information on allowable values, see * the class description for {@link ComponentEvent} * @throws IllegalArgumentException if {@code source} is null * @see #getComponent() * @see #getID() */ public ComponentEvent(Component source, int id) { super(source, id); } /** * Returns the originator of the event. * * @return the {@code Component} object that originated * the event, or {@code null} if the object is not a * {@code Component}. */ public Component getComponent() { return (source instanceof Component) ? (Component) source : null; } /** * Returns a parameter string identifying this 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; Rectangle b = (source != null ? ((Component) source).getBounds() : null); switch (id) { case COMPONENT_SHOWN: typeStr = "COMPONENT_SHOWN"; break; case COMPONENT_HIDDEN: typeStr = "COMPONENT_HIDDEN"; break; case COMPONENT_MOVED: typeStr = "COMPONENT_MOVED (" + b.x + "," + b.y + " " + b.width + "x" + b.height + ")"; break; case COMPONENT_RESIZED: typeStr = "COMPONENT_RESIZED (" + b.x + "," + b.y + " " + b.width + "x" + b.height + ")"; break; default: typeStr = "unknown type"; } return typeStr; } }