starting out with programming logic & design second edition by tony gaddis
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Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley
Starting Out with Programming Logic & Design
Second Edition
by Tony Gaddis
Chapter 15: GUI Applications & Event-Driven Programming
Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 15-2
Chapter Topics
15.1 Graphical User Interfaces
15.2 Designing the User Interface for a GUI Program
15.3 Writing Event Handlers
Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 15-3
15.1 Graphical User InterfacesA Graphical User Interface (GUI) allows the user to
interact with the operating system and other programs using graphical elements such as icons, buttons, and dialog boxes– Much of the work of a GUI is done through dialog boxes,
which are small windows that display information and allow the user to perform actions
– In a command line interface, the programs determine the order in which things happen
– In a GUI, the user can determine the order – this is called event driven
Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 15-4
15.1 Graphical User Interfaces
Figure 15-3 A GUI program
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15.1 Graphical User Interfaces
Creating a GUI Program– Most of the steps are the same– But, the programmer also designs the GUI
elements that make up each window– This includes the flow from window to window
Figure 15-4 A user interface flow diagram
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15.2 Designing the User Interface for a GUI Interface
GUI development also includes the program’s windows and all the graphical components– In the past, this was a cumbersome process– Newer languages allow for easier development
• Using Microsoft Visual Studio– Visual Basic
– C++
– C#
• Using NetBeans and JBuilder– Java
Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 15-7
15.2 Designing the User Interface for a GUI Interface
Most IDE’s have a toolbox for easy development
Figure 15-5 Visually constructing a window in Visual Basic
Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 15-8
15.2 Designing the User Interface for a GUI Interface
Components are items that appear in a program’s graphical user interface– Button: causes an action to occur when clicked– Label: can display text– Text Box: Allows the user to enter a single line of input– Check Box: Allows one or more options to be selected – Radio Button: Allows only one option to be selected– Combo Box: A dropdown list of items that the user can
select an item from, or enter input– List Box: A list from which the user can select an item– Slider: Allows the user to select a value from a range
Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 15-9
15.2 Designing the User Interface for a GUI Interface
Figure 15-7 Various components in a GUI window
Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 15-10
15.2 Designing the User Interface for a GUI Interface
Component names are used to identify the components in the program, in the same way variable names are used
Figure 15-8 Components and their names
Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 15-11
15.2 Designing the User Interface for a GUI Interface
Properties can be set on components to modify how it appears on the screen– Sets things like color, size, and position
A summary of constructing a window– Sketch the window– Create the necessary components and name them– Set the components’ properties to the desired
values
Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 15-12
15.3 Writing Event Handlers
Event handlers are written to control the GUI– After the windows are designed, event handlers are
coded to respond to events when an action occurs, such as clicking a button
– Event: an action that takes place within a program– Event handlers: a module that automatically
executes when a specific event occurs
Copyright © 2010 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 15-13
15.3 Writing Event Handlers
How to write the event handler moduleModule ComponentName_EventName()
The statements that appear here
are executed when the event occurs.
End Module
//an event handler that closes a window
Module exitButton_Click()
Close
End Module
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