Chapter 19
java.awt Reference

AWTEventMulticaster

Name

AWTEventMulticaster (New)

[Graphic: Figure from the text]

Description

This class multicasts events to event listeners. Each multicaster has two listeners, cunningly named a and b. When an event source calls one of the listener methods of the multicaster, the multicaster calls the same listener method on both a and b. Multicasters are built into trees using the static add() and remove() methods. In this way a single event can be sent to many listeners.

Static methods make it easy to implement event multicasting in component subclasses. Each time an add<type>Listener() function is called in the component subclass, call the corresponding AWTEventMulticaster.add() method to chain together (or "tree up") listeners. Similarly, when a remove<type>Listener() function is called, AWTEventMulticaster.remove() can be called to remove a chained listener.

Class Definition

public class java.awt.AWTEventMulticaster
  extends java.lang.Object
  implements java.awt.event.ActionListener, java.awt.event.AdjustmentListener,
             java.awt.event.ComponentListener, java.awt.event.ContainerListener,
             java.awt.event.FocusListener, java.awt.event.ItemListener,
             java.awt.event.KeyListener, java.awt.event.MouseListener,
             java.awt.event.MouseMotionListener, java.awt.event.TextListener,
             java.awt.event.WindowListener {
  // Variables
  protected EventListener a;
  protected EventListener b;
  // Constructors
  protected AWTEventMulticaster(EventListener a, EventListener b);
  // Class Methods
  public static ActionListener add(ActionListener a, ActionListener b);
  public static AdjustmentListener add(AdjustmentListener a, 
      AdjustmentListener b);
  public static ComponentListener add(ComponentListener a, 
      ComponentListener b);
  public static ContainerListener add(ContainerListener a, 
      ContainerListener b);
  public static FocusListener add(FocusListener a, FocusListener b);
  public static ItemListener add(ItemListener a, ItemListener b);
  public static KeyListener add(KeyListener a, KeyListener b);
  public static MouseListener add(MouseListener a, MouseListener b);
  public static MouseMotionListener add(MouseMotionListener a, 
      MouseMotionListener b);
  public static TextListener add(TextListener a, TextListener b);
  public static WindowListener add(WindowListener a, WindowListener b);
  protected static EventListener addInternal(EventListener a, EventListener b);
  public static ActionListener remove(ActionListener l, ActionListener oldl);
  public static AdjustmentListener remove(AdjustmentListener l, 
      AdjustmentListener oldl);
  public static ComponentListener remove(ComponentListener l, 
      ComponentListener oldl);
  public static ContainerListener remove(ContainerListener l, 
      ContainerListener oldl);
  public static FocusListener remove(FocusListener l, FocusListener oldl);
  public static ItemListener remove(ItemListener l, ItemListener oldl);
  public static KeyListener remove(KeyListener l, KeyListener oldl);
  public static MouseListener remove(MouseListener l, MouseListener oldl);
  public static MouseMotionListener remove(MouseMotionListener l, 
      MouseMotionListener oldl);
  public static TextListener remove(TextListener l, TextListener oldl);
  public static WindowListener remove(WindowListener l, WindowListener;
  protected static EventListener removeInternal(EventListener l, 
      EventListener oldl);
  // Instance Methods
  public void actionPerformed(ActionEvent e);
  public void adjustmentValueChanged(AdjustmentEvent e);
  public void componentAdded(ContainerEvent e);
  public void componentHidden(ComponentEvent e);
  public void componentMoved(ComponentEvent e);
  public void componentRemoved(ContainerEvent e);
  public void componentResized(ComponentEvent e);
  public void componentShown(ComponentEvent e);
  public void focusGained(FocusEvent e);
  public void focusLost(FocusEvent e);
  public void itemStateChanged(ItemEvent e);
  public void keyPressed(KeyEvent e);
  public void keyReleased(KeyEvent e);
  public void keyTyped(KeyEvent e);
  public void mouseClicked(MouseEvent e);
  public void mouseDragged(MouseEvent e);
  public void mouseEntered(MouseEvent e);
  public void mouseExited(MouseEvent e);
  public void mouseMoved(MouseEvent e);
  public void mousePressed(MouseEvent e);
  public void mouseReleased(MouseEvent e);
  public void textValueChanged(TextEvent e);
  public void windowActivated(WindowEvent e);
  public void windowClosed(WindowEvent e);
  public void windowClosing(WindowEvent e);
  public void windowDeactivated(WindowEvent e);
  public void windowDeiconified(WindowEvent e);
  public void windowIconified(WindowEvent e);
  public void windowOpened(WindowEvent e);
  // Protected Instance Methods
  protected EventListener remove(EventListener oldl);
  protected void saveInternal(ObjectOutputStream s, String k) throws IOException;
}

Variables

a

protected EventListener a

One of the EventListeners this AWTEventMulticaster sends events to.

b

protected EventListener b

One of the EventListeners this AWTEventMulticaster sends events to.

Constructors

AWTEventMulticaster

protected AWTEventMulticaster (EventListener a, EventListener b)

Parameters

a

A listener that receives events.

b

A listener that receives events.

Description

Constructs an AWTEventMulticaster that sends events it receives to the supplied listeners. The constructor is protected because it is only the class methods of AWTEventMulticaster that ever instantiate this class.

An event listener.

b

An event listener.

Returns

A listener object that passes events to a and b.

public static AdjustmentListener add (AdjustmentListener a, AdjustmentListener b)

Parameters

a

An event listener.

b

An event listener.

Returns

A listener object that passes events to a and b.

public static ComponentListener add (ComponentListener a, ComponentListener b)

Parameters

a

An event listener.

b

An event listener.

Returns

A listener object that passes events to a and b.

public static ContainerListener add (ContainerListener a, ContainerListener b)

Parameters

a

An event listener.

b

An event listener.

Returns

A listener object that passes events to a and b.

public static FocusListener add (FocusListener a, FocusListener b)

Parameters

a

An event listener.

b

An event listener.

Returns

A listener object that passes events to a and b.

public static ItemListener add (ItemListener a, ItemListener b)

Parameters

a

An event listener.

b

An event listener.

Returns

A listener object that passes events to a and b.

public static KeyListener add (KeyListener a, KeyListener b)

Parameters

a

An event listener.

b

An event listener.

Returns

A listener object that passes events to a and b.

public static MouseListener add (MouseListener a, MouseListener b)

Parameters

a

An event listener.

b

An event listener.

Returns

A listener object that passes events to a and b.

public static MouseMotionListener add (MouseMotionListener a, MouseMotionListener b)

Parameters

a

An event listener.

b

An event listener.

Returns

A listener object that passes events to a and b.

public static TextListener add (TextListener a, TextListener b)

Parameters

a

An event listener.

b

An event listener.

Returns

A listener object that passes events to a and b.

public static WindowListener add (WindowListener a, WindowListener b)

Parameters

a

An event listener.

b

An event listener.

Returns

A listener object that passes events to a and b.

addInternal

public static EventListener addInternal (EventListener a, EventListener b)

Parameters

a

An event listener.

public static EventListener removeInternal (EventListener l, EventListener oldl)

Parameters

l

An event listener.

oldl

An event listener.

Returns

A listener object that multicasts to l but not oldl.

Description

This method is a helper for the remove() methods.

e: The action event that occurred.

Description