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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.
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.
An unspecified behavior will be caused if the id parameter of any particular ContainerEvent instance is not in the range from CONTAINER_FIRST to CONTAINER_LAST.
Author: Tim Prinzing, Amy Fowler See Also: Since: 1.1
/**
* 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}
* or {@code ContainerAdapter} object which registered to receive such
* events using the component's {@code addContainerListener} method.
* ({@code ContainerAdapter} objects implement the
* {@code ContainerListener} interface.) Each such listener object
* gets this {@code ContainerEvent} 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="http://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.
/**
* 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.
/**
* 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.
/**
* 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.
/**
* 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.
See Also: @serial
/**
* 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. This method throws an IllegalArgumentException if source is null.
Params: - source – The
Component object (container) that originated the event - id – An integer indicating the type of event. For information on allowable values, see the class description for
ContainerEvent - child – the component that was added or removed
Throws: - IllegalArgumentException – if
source is null
See Also:
/**
* Constructs a {@code ContainerEvent} object.
* <p> This method throws an
* {@code IllegalArgumentException} if {@code source}
* is {@code null}.
*
* @param source The {@code Component} 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} 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.
Returns: the Container object that originated the event, or null if the object is not a Container.
/**
* Returns the originator of the event.
*
* @return the {@code Container} object that originated
* the event, or {@code null} if the object is not a
* {@code Container}.
*/
public Container getContainer() {
return (source instanceof Container) ? (Container)source : null;
}
Returns the component that was affected by the event.
Returns: the Component object that was added or removed
/**
* 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.
Returns: a string identifying the event and its attributes
/**
* 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();
}
}