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ComponentEvent.javaAPI DocJava SE 5 API4937Fri Aug 26 14:56:50 BST 2005java.awt.event

ComponentEvent

public class ComponentEvent extends AWTEvent
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.

see
ComponentAdapter
see
ComponentListener
see
Tutorial: Writing a Component Listener
see
Reference: The Java Class Libraries (update file)
author
Carl Quinn
version
1.27 12/19/03
since
1.1

Fields Summary
public static final int
COMPONENT_FIRST
The first number in the range of ids used for component events.
public static final int
COMPONENT_LAST
The last number in the range of ids used for component events.
public static final int
COMPONENT_MOVED
This event indicates that the component's position changed.
public static final int
COMPONENT_RESIZED
This event indicates that the component's size changed.
public static final int
COMPONENT_SHOWN
This event indicates that the component was made visible.
public static final int
COMPONENT_HIDDEN
This event indicates that the component was rendered invisible.
private static final long
serialVersionUID
Constructors Summary
public ComponentEvent(Component source, int id)
Constructs a ComponentEvent 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 that originated the event
param
id an integer indicating the type of event
throws
IllegalArgumentException if source is null


                                                            
         
        super(source, id);
Methods Summary
public java.awt.ComponentgetComponent()
Returns the originator of the event.

return
the Component object that originated the event, or null if the object is not a Component.

        return (source instanceof Component) ? (Component)source : null;
public java.lang.StringparamString()
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

        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;