META-INF.modules.java.desktop.classes.java.awt.event.ContainerEvent Maven / Gradle / Ivy
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package java.awt.event;
import java.awt.Component;
import java.awt.Container;
import java.io.Serial;
/**
* 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 {@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.
*
* 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 Tutorial: Writing a Container Listener
*
* @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;
/**
* Use serialVersionUID from JDK 1.1 for interoperability.
*/
@Serial
private static final long serialVersionUID = -4114942250539772041L;
/**
* Constructs a {@code ContainerEvent} object.
*
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.
*
* @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.
*
* @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();
}
}