EventListeners

To respond to an event a component receives you register an event listener for the event type with the component. Event listeners are objects which implement a java.util.EventListener interface. The AWT defines eleven sub-interfaces of java.util.EventListener, one for each type of event:


            	java.awt.event.ComponentListener 

            	
java.awt.event.ContainerListener 

            	
java.awt.event.FocusListener 

            	
java.awt.event.KeyListener 

            	
java.awt.event.MouseListener 

            	
java.awt.event.MouseMotionListener 

            	
java.awt.event.WindowListener

            	
java.awt.event.ActionListener 

            	
java.awt.event.AdjustmentListener 

            	
java.awt.event.ItemListener 

            	
java.awt.event.TextListener

Each of these interfaces defines the events an event listener of that type must be prepared to respond to. For example, MouseListener declares these methods,

 public abstract void mouseClicked(MouseEvent e)
 public abstract void mousePressed(MouseEvent e)
 public abstract void mouseReleased(MouseEvent e)
 public abstract void mouseEntered(MouseEvent e)
 public abstract void mouseExited(MouseEvent e)

When a component receives a mouse event, its processMouseEvent() method checks the ID of the mouse event to determine whether this is a mouse pressed, mouse released, mouse entered, or mouse exited event. Then it calls the corresponding method in each registered MouseListener object.

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Last Modified August 7, 1997
Copyright 1997 Elliotte Rusty Harold
elharo@sunsite.unc.edu