/* * @(#)ContainerEvent.java 1.18 03/12/19 * * Copyright 2004 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. *
* 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. *
* 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 ContainerListener
* or ContainerAdapter
object which registered to receive such
* events using the component's addContainerListener
method.
* (ContainerAdapter
objects implement the
* ContainerListener
interface.) Each such listener object
* gets this ContainerEvent
when the event occurs.
*
* @see ContainerAdapter
* @see ContainerListener
* @see Tutorial: Writing a Container Listener
* @see Reference: The Java Class Libraries (update file)
*
* @author Tim Prinzing
* @author Amy Fowler
* @version 1.18 12/19/03
* @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 ContainerEvent
object.
*
Note that passing in an invalid id
results in
* unspecified behavior. This method throws an
* IllegalArgumentException
if source
* is null
.
*
* @param source the Component
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 source
is null
*/
public ContainerEvent(Component source, int id, Component child) {
super(source, id);
this.child = child;
}
/**
* Returns the originator of the event.
*
* @return the Container
object that originated
* the event, or null
if the object is not a
* Container
.
*/
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();
}
}