programming-for-dummies

42
Making User Interfaces with Event-Driven Programming
With event-driven programming, designing a user interface involves drawing
your user interface and then customizing it by changing its properties. After
you’ve designed your user interface, it will appear to work but it won’t actually
do anything until you write an event handler.
Writing event handlers
The whole purpose of an event handler is to work as a middleman between
your actual program and your program’s user interface. To create an event
handler, you need to identify the following:
✦ A user interface item, such as a button or a check box
✦ The event, such as a click of the mouse
The combination of a user interface item and a specific event uniquely
defines an event handler, as shown in Figure 2-7.
User interface
item (button)
Event
(click)
Figure 2-7:
An event
handler tells
the user
interface
how to
behave
when the
user does
something,
such as
click the
mouse over
a button.