Event Listener Object

When a GUI program is running, the user generates an event by interacting with a GUI component. The following are some ways to generate an event:

• Moving the mouse.
• Clicking the mouse.
• Clicking a button.
• Typing some text into a text area.

For a program to respond to an event there must be an event listener object in the GUI program. The event listener contains listener methods that are specialized to various types of events.

A program can ignore events. For example the programs of the previous chapter ignored nearly all events. If there is no listener for an event, the Java system ignores it.