Actions and Events

• Java programs respond to command parameters and file interactions
• Java applets respond to events
• Every action within the view window (keystroke, mouse button, mouse drag, etc.) may either be processed or ignored
• To handle action events, provide an overriding action method with this signature:

  public boolean action(Event evt, Object arg)

  • the Event parameter indicates which kind of action event occurred
  • the Object parameter indicates a potential parameter value associated with the action
• There are also more specific action handlers (e.g. keyDown, mouseDrag, etc.) which can have overriding methods
• To handle all events, supply an overriding handleEvent method:

  public boolean handleEvent(Event evt)

• Both of these methods should return true if the event was handled, and false if it was not; this tells the Java run-time system to look for handlers further up the class hierarchy