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package java.awt.event;
import java.awt.AWTEvent;
import java.awt.Component;
import java.awt.Rectangle;
import java.lang.annotation.Native;
A low-level event which indicates that a component moved, changed
size, or changed visibility (also, the root class for the other
component-level events).
Component events are provided for notification purposes ONLY;
The AWT will automatically handle component moves and resizes
internally so that GUI layout works properly regardless of
whether a program is receiving these events or not.
In addition to serving as the base class for other component-related
events (InputEvent, FocusEvent, WindowEvent, ContainerEvent),
this class defines the events that indicate changes in
a component's size, position, or visibility.
This low-level event is generated by a component object (such as a List) when the component is moved, resized, rendered invisible, or made visible again. The event is passed to every ComponentListener or ComponentAdapter object which registered to receive such events using the component's addComponentListener method. (ComponentAdapter objects implement the ComponentListener interface.) Each such listener object gets this ComponentEvent when the event occurs.
An unspecified behavior will be caused if the id parameter of any particular ComponentEvent instance is not in the range from COMPONENT_FIRST to COMPONENT_LAST.
Author: Carl Quinn See Also: Since: 1.1
/**
* A low-level event which indicates that a component moved, changed
* size, or changed visibility (also, the root class for the other
* component-level events).
* <P>
* Component events are provided for notification purposes ONLY;
* The AWT will automatically handle component moves and resizes
* internally so that GUI layout works properly regardless of
* whether a program is receiving these events or not.
* <P>
* In addition to serving as the base class for other component-related
* events (InputEvent, FocusEvent, WindowEvent, ContainerEvent),
* this class defines the events that indicate changes in
* a component's size, position, or visibility.
* <P>
* This low-level event is generated by a component object (such as a
* List) when the component is moved, resized, rendered invisible, or made
* visible again. The event is passed to every {@code ComponentListener}
* or {@code ComponentAdapter} object which registered to receive such
* events using the component's {@code addComponentListener} method.
* ({@code ComponentAdapter} objects implement the
* {@code ComponentListener} interface.) Each such listener object
* gets this {@code ComponentEvent} when the event occurs.
* <p>
* An unspecified behavior will be caused if the {@code id} parameter
* of any particular {@code ComponentEvent} instance is not
* in the range from {@code COMPONENT_FIRST} to {@code COMPONENT_LAST}.
*
* @see ComponentAdapter
* @see ComponentListener
* @see <a href="http://docs.oracle.com/javase/tutorial/uiswing/events/componentlistener.html">Tutorial: Writing a Component Listener</a>
*
* @author Carl Quinn
* @since 1.1
*/
public class ComponentEvent extends AWTEvent {
The first number in the range of ids used for component events.
/**
* The first number in the range of ids used for component events.
*/
public static final int COMPONENT_FIRST = 100;
The last number in the range of ids used for component events.
/**
* The last number in the range of ids used for component events.
*/
public static final int COMPONENT_LAST = 103;
This event indicates that the component's position changed.
/**
* This event indicates that the component's position changed.
*/
@Native public static final int COMPONENT_MOVED = COMPONENT_FIRST;
This event indicates that the component's size changed.
/**
* This event indicates that the component's size changed.
*/
@Native public static final int COMPONENT_RESIZED = 1 + COMPONENT_FIRST;
This event indicates that the component was made visible.
/**
* This event indicates that the component was made visible.
*/
@Native public static final int COMPONENT_SHOWN = 2 + COMPONENT_FIRST;
This event indicates that the component was rendered invisible.
/**
* This event indicates that the component was rendered invisible.
*/
@Native public static final int COMPONENT_HIDDEN = 3 + COMPONENT_FIRST;
/*
* JDK 1.1 serialVersionUID
*/
private static final long serialVersionUID = 8101406823902992965L;
Constructs a ComponentEvent object. This method throws an IllegalArgumentException if source is null.
Params: - source – The
Component that originated the event - id – An integer indicating the type of event. For information on allowable values, see the class description for
ComponentEvent
Throws: - IllegalArgumentException – if
source is null
See Also:
/**
* Constructs a {@code ComponentEvent} object.
* <p> This method throws an
* {@code IllegalArgumentException} if {@code source}
* is {@code null}.
*
* @param source The {@code Component} that originated the event
* @param id An integer indicating the type of event.
* For information on allowable values, see
* the class description for {@link ComponentEvent}
* @throws IllegalArgumentException if {@code source} is null
* @see #getComponent()
* @see #getID()
*/
public ComponentEvent(Component source, int id) {
super(source, id);
}
Returns the originator of the event.
Returns: the Component object that originated the event, or null if the object is not a Component.
/**
* Returns the originator of the event.
*
* @return the {@code Component} object that originated
* the event, or {@code null} if the object is not a
* {@code Component}.
*/
public Component getComponent() {
return (source instanceof Component) ? (Component)source : null;
}
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;
Rectangle b = (source !=null
? ((Component)source).getBounds()
: null);
switch(id) {
case COMPONENT_SHOWN:
typeStr = "COMPONENT_SHOWN";
break;
case COMPONENT_HIDDEN:
typeStr = "COMPONENT_HIDDEN";
break;
case COMPONENT_MOVED:
typeStr = "COMPONENT_MOVED ("+
b.x+","+b.y+" "+b.width+"x"+b.height+")";
break;
case COMPONENT_RESIZED:
typeStr = "COMPONENT_RESIZED ("+
b.x+","+b.y+" "+b.width+"x"+b.height+")";
break;
default:
typeStr = "unknown type";
}
return typeStr;
}
}