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/* * @(#)ContainerEvent.java 1.20 06/04/13 * * Copyright 2006 Sun Microsystems, Inc. All rights reserved. * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. */ package java.awt.event; import java.awt.AWTEvent; import java.awt.Container; import java.awt.Component; /** * A low-level event which indicates that a container's contents * changed because a component was added or removed. * <P> * Container events are provided for notification purposes ONLY; * The AWT will automatically handle changes to the containers * contents internally so that the program works properly regardless of * whether the program is receiving these events or not. * <P> * This low-level event is generated by a container object (such as a * Panel) when a component is added to it or removed from it. * The event is passed to every <code>ContainerListener</code> * or <code>ContainerAdapter</code> object which registered to receive such * events using the component's <code>addContainerListener</code> method. * (<code>ContainerAdapter</code> objects implement the * <code>ContainerListener</code> interface.) Each such listener object * gets this <code>ContainerEvent</code> when the event occurs. * * @see ContainerAdapter * @see ContainerListener * @see <a href="http://java.sun.com/docs/books/tutorial/post1.0/ui/containerlistener.html">Tutorial: Writing a Container Listener</a> * * @author Tim Prinzing * @author Amy Fowler * @version 1.20 04/13/06 * @since 1.1 */ public class ContainerEvent extends ComponentEvent { /** * The first number in the range of ids used for container events. */ public static final int CONTAINER_FIRST = 300; /** * The last number in the range of ids used for container events. */ public static final int CONTAINER_LAST = 301; /** * This event indicates that a component was added to the container. */ public static final int COMPONENT_ADDED = CONTAINER_FIRST; /** * This event indicates that a component was removed from the container. */ public static final int COMPONENT_REMOVED = 1 + CONTAINER_FIRST; /** * The non-null component that is being added or * removed from the Container. * * @serial * @see #getChild() */ Component child; /* * JDK 1.1 serialVersionUID */ private static final long serialVersionUID = -4114942250539772041L; /** * Constructs a <code>ContainerEvent</code> object. * <p>Note that passing in an invalid <code>id</code> results in * unspecified behavior. This method throws an * <code>IllegalArgumentException</code> if <code>source</code> * is <code>null</code>. * * @param source the <code>Component</code> object (container) * that originated the event * @param id an integer indicating the type of event * @param child the component that was added or removed * @throws IllegalArgumentException if <code>source</code> is null */ public ContainerEvent(Component source, int id, Component child) { super(source, id); this.child = child; } /** * Returns the originator of the event. * * @return the <code>Container</code> object that originated * the event, or <code>null</code> if the object is not a * <code>Container</code>. */ public Container getContainer() { return (source instanceof Container) ? (Container)source : null; } /** * Returns the component that was affected by the event. * * @return the Component object that was added or removed */ public Component getChild() { return child; } /** * 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; switch(id) { case COMPONENT_ADDED: typeStr = "COMPONENT_ADDED"; break; case COMPONENT_REMOVED: typeStr = "COMPONENT_REMOVED"; break; default: typeStr = "unknown type"; } return typeStr + ",child="+child.getName(); } }