1. Chapter 8: Writing Graphical User Interfaces
Visual Basic .NET Programming:
From Problem Analysis to Program Design

2. Visual Basic .NET Programming: From Problem Analysis to Program Design
Objectives
Learn about the GUI classes in VB .NET
Understand the code generated by the Windows Form Designer
Explore GUI design principles
Review forms, buttons, and labels
Handle events
Work with additional GUI controls
Visual Basic .NET Programming: From Problem Analysis to Program Design

3. Introducing the GUI Classes in VB .NET
Form class
Member of System.Windows.Forms namespace
Used to implement a window
GUI classes take advantage of inheritance
Most are subclasses of Control class
Inheritance
Class of objects takes on characteristics of another class and extends them
Visual Basic .NET Programming: From Problem Analysis to Program Design

4. Visual Basic .NET Programming: From Problem Analysis to Program Design

5. Visual Basic .NET Programming: From Problem Analysis to Program Design

6. Visual Basic .NET Programming: From Problem Analysis to Program Design

7. Understanding the Code Generated by the Windows Form Designer
Use drag-and-drop features of Windows Form Designer to create GUIs
Visual programming consists of:
Creating a form
Setting its properties
Adding components
Setting component properties
Adding event handling code
Visual Basic .NET Programming: From Problem Analysis to Program Design

8. Visual Basic .NET Programming: From Problem Analysis to Program Design
Understanding the Code Generated by the Windows Form Designer (continued)
VB .NET generates code that handles details of form design
Called class definition
Specifies attributes and methods that make form work
Visual Basic .NET Programming: From Problem Analysis to Program Design

9. Exploring the FormDemo Program
Class definition
Begins with class header
Ends with End Class statement
Class keyword
Identifies first line of code as class header
Followed by class name
Public keyword
Class can be used by anyone
Visual Basic .NET Programming: From Problem Analysis to Program Design

10. Exploring the FormDemo Program (continued)
Inherits keyword
Indicates name of superclass
When working in IDE:
Most generated code collapsed under heading “Windows Form Designer generated code”
Begins with #Region directive
Ends with #End Region directive
View by clicking expand node
Generated code is complex
Visual Basic .NET Programming: From Problem Analysis to Program Design

11. Exploring the FormDemo Program (continued)
Constructor
Special method
Automatically invoked when instance of class is created
Windows Form Designer provides default constructor for each form
Method is named New
Visual Basic .NET Programming: From Problem Analysis to Program Design

12. Exploring the FormDemo Program (continued)
MyBase keyword
Refers to superclass of current object
MyBase.New( ) calls superclass constructor
Dispose method
Destructor
Releases system resources
Container
Object that holds other components
Visual Basic .NET Programming: From Problem Analysis to Program Design

13. Exploring the FormDemo Program (continued)
Friend keyword
Specifies that object is accessible only within files that compose application
WithEvents keyword
Control instance may be source of events
Events will be handled by methods that include Handles controlName.eventName clause
Visual Basic .NET Programming: From Problem Analysis to Program Design

14. Exploring the FormDemo Program (continued)
Private keyword
Indicates that method is accessible only within own class
Me keyword
Refers to current object
Parameter list
Identifies variables that receive values when method invoked
Visual Basic .NET Programming: From Problem Analysis to Program Design

15. Exploring GUI Design Principles
Many standards that guide creative process of user interface design
Basic principles include:
Creating consistent look and feel
Ensuring ease of use
Minimizing data entry errors
Providing feedback to users
Adhering to standard naming conventions
Visual Basic .NET Programming: From Problem Analysis to Program Design

16. Creating a Consistent Look and Feel
Style and appearance of form
Includes choice of colors and fonts for various controls
Key design goal
Provide consistent look and feel as user moves among various forms
Visual Basic .NET Programming: From Problem Analysis to Program Design

17. Ensuring Ease of Use and Minimizing Data-Entry Errors
Purpose of each control and layout of form should be intuitive
Placement and grouping of controls should be logical
Form should appear uncluttered
Good practice:
Design input forms to minimize required keystrokes
Visual Basic .NET Programming: From Problem Analysis to Program Design

18. Providing Feedback to the User
Provide feedback to user
When certain actions have been completed
To inform user when data entry errors have occurred
Present feedback in consistent manner
Visual Basic .NET Programming: From Problem Analysis to Program Design

19. Visual Basic .NET Programming: From Problem Analysis to Program Design
Naming Conventions
Adhering to set of naming conventions
Improves program readability
Facilitates program maintenance
Assign meaningful variable names
Change Name property for each control
Variable name should reflect both
Type of control
Purpose of control
Visual Basic .NET Programming: From Problem Analysis to Program Design

20. Visual Basic .NET Programming: From Problem Analysis to Program Design

21. Reviewing Forms, Buttons, and Labels
All GUI components with visual representation are subclasses of Control class
Control class is a subclass of Component class
Set many properties in Properties window
Can also manipulate properties through code in event handlers
Visual Basic .NET Programming: From Problem Analysis to Program Design

22. Visual Basic .NET Programming: From Problem Analysis to Program Design

23. Visual Basic .NET Programming: From Problem Analysis to Program Design

24. Visual Basic .NET Programming: From Problem Analysis to Program Design
Handling Events
To create event handling procedure:
Double-click control in Forms Designer window
VB .NET places method header in Code window
Add statements that handle event
Code is added to most commonly used event handler for control
Visual Basic .NET Programming: From Problem Analysis to Program Design

25. Handling Events (continued)
Alternate method for adding event-handling code:
Press F7 to open Code window
Select class name from Class Name list box
Select event from Method Name list box
Add statements that handle event
Visual Basic .NET Programming: From Problem Analysis to Program Design

26. Visual Basic .NET Programming: From Problem Analysis to Program Design

27. Visual Basic .NET Programming: From Problem Analysis to Program Design

28. Working with Additional GUI Controls
Other commonly used controls:
Text boxes
Combo boxes
Check boxes
Radio buttons
List boxes
Visual Basic .NET Programming: From Problem Analysis to Program Design

29. Using Text Boxes and Combo Boxes
Used to display textual information
Enable inputting of text from keyboard
Combo box
Extends functionality of text box
Provides ability to select item from predetermined list of values
Can also type value
Visual Basic .NET Programming: From Problem Analysis to Program Design

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31. Visual Basic .NET Programming: From Problem Analysis to Program Design

32. Visual Basic .NET Programming: From Problem Analysis to Program Design

33. Using Check Boxes and Radio Buttons
Check boxes and radio buttons provide ability to select from options
States:
Checked/Selected
Unchecked/Not selected
Check box
Appears as small white box
Usually includes label that identifies purpose
Visual Basic .NET Programming: From Problem Analysis to Program Design

34. Using Check Boxes and Radio Buttons (continued)
Appear as small white circles
Have captions that identify purpose
Group of radio buttons
Represents set of related options
Options are mutually exclusive
Visual Basic .NET Programming: From Problem Analysis to Program Design

35. Visual Basic .NET Programming: From Problem Analysis to Program Design

36. Visual Basic .NET Programming: From Problem Analysis to Program Design

37. Visual Basic .NET Programming: From Problem Analysis to Program Design

38. Using List Boxes and Checked List Boxes
Provide ability to select one or more items from predetermined list of values
List box
Select one or more items from list
Checked list boxes
Include check box to left of each item in list
Visual Basic .NET Programming: From Problem Analysis to Program Design

39. Visual Basic .NET Programming: From Problem Analysis to Program Design

40. Visual Basic .NET Programming: From Problem Analysis to Program Design

41. Example 8-5: The Fast Food Menu Program
For Each statement
Similar to For Next
Loops through a collection of items
Specifies:
Variable
Collection
Visual Basic .NET Programming: From Problem Analysis to Program Design

42. Programming Example: ABC Computers
Input
Type of processor
Operating system
Peripherals desired
State of residence
Output
Order summary
Total cost
Visual Basic .NET Programming: From Problem Analysis to Program Design

43. Visual Basic .NET Programming: From Problem Analysis to Program Design

44. Programming Example: ABC Computers (continued)
Main Algorithm
Define cost variables at the class level
Create an event handler for each control that captures data from the user
When the user selects an option from one of the GUI controls, let the event handler for that control:
Determine the price of that option
Calculate total cost and display the order summary
Visual Basic .NET Programming: From Problem Analysis to Program Design

45. Visual Basic .NET Programming: From Problem Analysis to Program Design
Summary
VB .NET generates a class definition
Specifies attributes and methods that make forms work
Generated code collapsed under heading “Windows Form Designer generated code”
Generated code is complex
Constructor
Special method automatically invoked when instance of class is created
Visual Basic .NET Programming: From Problem Analysis to Program Design

46. Visual Basic .NET Programming: From Problem Analysis to Program Design
Summary (continued)
Container
Object that holds other components
Look and feel
Style and appearance of form
Use standards to ensure consistent look and feel
Follow naming conventions for controls
Visual Basic .NET Programming: From Problem Analysis to Program Design

47. Visual Basic .NET Programming: From Problem Analysis to Program Design
Summary (continued)
Form components include:
Text box
Combo box
Check box
Radio button
List box
Checked list box
Visual Basic .NET Programming: From Problem Analysis to Program Design