Three Parts of a GUI Program
A GUI program consists of three types of software:
- Graphical Components make up the Graphical User Interface.
- Listener methods receive the events and respond to them.
- Application methods do useful work for the user.
The graphical components are Swing objects. You may use them without change or may extend them to make your own classes. Listener methods and application methods are Java methods that you write. Listener methods respond to events by calling application methods. Application methods are ordinary Java methods that perform useful computations. They receive data from the GUI and send data to the GUI to be displayed, but are not usually themselves concerned with the user interface.
Your Web browser has components (such as the "back" and "forward" buttons), listener methods that receive events (such as a click on the "back" button) and application methods that do useful things (such as moving backward or forward one page).
To write a GUI application, keep these three types of software separated (while keeping the big picture in mind). In a big software project an entire team of programmers is assigned to each of the tasks.
