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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*/
package java.awt.event;
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.
* <p>
* An unspecified behavior will be caused if the {@code id} parameter
* of any particular {@code ContainerEvent} instance is not
* in the range from {@code CONTAINER_FIRST} to {@code CONTAINER_LAST}.
*
* @see ContainerAdapter
* @see ContainerListener
* @see <a href="https://docs.oracle.com/javase/tutorial/uiswing/events/containerlistener.html">Tutorial: Writing a Container Listener</a>
*
* @author Tim Prinzing
* @author Amy Fowler
* @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> 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.
* For information on allowable values, see
* the class description for {@link ContainerEvent}
* @param child the component that was added or removed
* @throws IllegalArgumentException if <code>source</code> is null
* @see #getContainer()
* @see #getID()
* @see #getChild()
*/
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();
}
}