CHAPTER FIVE

1
CHAPTER FIVE

• Mobile Applications Using Decision Structures

2
Objectives

• Write programs for devices other than a personal
  computer
• Understand the use of handheld technology ( aka
  smart devices )
• Write handheld applications for a Personal
  Digital Assistant
• Use the Panel object
• Place RadioButton objects in applications

3
Objectives

• Display a message box
• Make decisions using IfThen statements
• Make decisions using IfThenElse statements
• Make decisions using nested If statements

4
Objectives

• Make decisions using logical operators
• Make decisions using Case statements
• Insert code snippets
• Test input to ensure a value is numeric

5
Chapter Project
6
Pervasive Devices

• Visual Studio has a built-in emulator that
  displays a working Pocket PC
• Pervasive devices have become important in many
  business venues

7
Create a Smart Device Application

• New Project
• if necessary, click the plus sign next to Smart
  Device in the Project types pane on the left side
  of the New Project dialog box
• Click Pocket PC 2003 under Smart Device in the
  Project types list. Windows Mobile 6
• In the Templates pane, click Device Application
• Change the Name of the Smart Device application
  from DeviceApplication1 to WoodCabinetEstimate.
  Click the OK button

8
Create a Smart Device Application
9
Placing Objects on the Pocket PC Form Object

• Many of the same objects used in a Windows
  application can be placed on the PocketPC Form
  object
• You cannot resize the Form object
• The PocketPC Form object can be named in the same
  manner as a Windows Form object using the (Name)
  property in the Properties window
• Change the Text property of the PocketPC Form
  object from Form1 to Estimate in the same manner
  used for the Windows Form object

10
Placing Objects on the PocketPC Form Object
11
Using the Panel Object

• If necessary, open the Device Containers category
  of the Toolbox by clicking the plus sign next to
  the category name.
• A Panel is used as a container for other
  controls. In this application it will be used to
  group radio buttons.
• (Name) property --- gt pnlWoodType

12
Using the Panel Object
13
Adding the 3 RadioButton Objects

• Drag and drop one RadioButton object from the
  Toolbox onto the PocketPC Form object inside the
  Panel object.
• Drag a second RadioButton object from the Toolbox
  onto the PocketPC Form object using blue snap
  lines to align and separate the RadioButton
  objects vertically
• add a third RadioButton object

14
Adding the RadioButton Objects

• Name the RadioButton objects (Name) property
• The names for the radio buttons, from top to
  bottom, should be
• radPine
• radOak
• radCherry
• Change the Text property for each RadioButton
• Pine
• Oak
• Cherry

15
Adding the RadioButton Objects
16
Windows Application Container Objects

• For Windows applications, Visual Basic provides 5
  additional container classes in addition to the
  Panel class.
• FlowLayoutPanel
• GroupBox
• SplitContainer
• TabControl
• TableLayoutPanel
• GroupBox is most popular

17
Windows Application Container Objects
GroupBox controls are typically used to group
radio buttons, but they are NOT available for
smart devices so for a smart device use a Panel
control
18
GroupBox versus Panel
19
Examples using MsgBox Function

• The following examples demonstrate displaying a
  message box using the VB 6 style MsgBox
  Function.
• Later examples will show using the .NET show
  method of the MessageBox class

20
MsgBox Message only

• MsgBox( Message )
• --------------------------------------------------
  ------------
• MsgBox(Enter the Linear Feet of the Cabinet)

21
Displaying a Message Box
22
MsgBox with Caption

• MsgBox( Message, ,Caption )
• --------------------------------------------------
  ----------------
• MsgBox(Enter the Linear Feet of the Cabinet _
  , , _ Error Missing
  a Number)
• Note the , , to indicate an optional positional
  parameter has been skipped ( will use default
  value )

23
Displaying a Message Box
24
MsgBox with Caption and Button

• MsgBox( Message, ltButton Entrygt , Caption )
• --------------------------------------------------
  --------------------
• MsgBox(User name is missing, _
  MsgBoxStyle.OKCancel, _ Entry
  Error)
• MsgBox(You have been disconnected, _
  MsgBoxStyle.RetryCancel, _
  ISP)
• MsgBox(You have been disconnected, _
  5, _ ISP)

25
Displaying a Message Box
26
MsgBoxStyle Button(s) Enumeration
27
MsgBox with Caption, Button, and Icon

• MsgBox( Message, ltButton Entry or Icon
  Picturegt , Caption )
• --------------------------------------------------
  ---------------------------------------
• MsgBox(User name is missing, _
  MsgBoxStyle.OKCancel or MsgBoxStyle.Critical, _
  or / User Name Error)
• MsgBox(User name is missing, _ 1
  or 16, _ also 1 16 or 17 User
  Name Error)
• MsgBox(You have been disconnected, _
  MsgBoxStyle.RetryCancel MsgBoxStyle.Question
  , _ / or ISP)
• MsgBox(You have been disconnected, _
  5 32, _ also 5 32 or 37
  ISP)

28
Displaying a Message Box
29
MsgBoxStyle Icon Enumeration
30
MessageBox Class Examples

• The following examples use the show method of the
  MessageBox class.
• The benefit of using this is it would available
  for use in C applications as well.
• This is the newer preferred method
• Oddly enough, this is what was used in the
  previous version of the book

31
MessageBox Class Syntax

• 1 4 Arguments ( overloaded ) common
  usage
• Message to be displayed
• Caption to display in the title bar blank
  if omitted
• MessageBoxButtons to be displayed OK if
  omitted
• MessageBoxIcon to be displayed blank if
  omitted or
• MessageBoxImage to be displayed blank if
  omitted .NET Framework V 3.0
• The Show method returns a value of type
  DialogResult

32
Values Returned by a MessageBox returns a value
of type DialogResult
33
Displaying a Message Box 1 Argument
The Show method takes up to 4 arguments
34
Displaying a Message Box
35
Displaying a Message Box 2 Arguments
36
Displaying a Message Box
37
Displaying a Message Box 3 Arguments
38
Displaying a Message Box
39
MessageBoxButtons Enumeration
40
Displaying a Message Box 4 Arguments
41
Displaying a Message Box
42
MessageBoxIcon Enumeration
There is also the member name None for which
no icon is displayed
43
Message Box IntelliSense

• In the code editing window, inside the event
  handler you are coding, press CTRLSPACEBAR.
  IntelliSense displays the allowable entries.
• Type mes to select MessageBox in the IntelliSense
  list
• Type a period ( . ) to insert the dot operator.
  IntelliSense displays a list of the allowable
  entries. Type s to select Show in the
  IntelliSense list
• Type the following text (You have been
  disconnected from the Internet, ISP,

44
Displaying a Message Box

• Here are the last two arguments for the Show
  method
• MessageBoxButtons.RetryCancel
• MessageBoxIcon.Warning
• MessageBox.Show (You have been disconnected from
  the Internet,_
• ISP,_
• MessageBoxButtons.RetryCancel,_
• MessageBoxIcon.Warning)
• Type a right parenthesis and then press the ENTER
  key

45
Displaying a Message Box
46
Displaying a Message Box 2 arguments
47
Making Decisions with Conditional Statements

• Using an IfThen Statement
• A decision structure is one of the three
  fundamental control structures used in computer
  programming. Sequence, Selection,
  Repetition
• When a condition is tested in a Visual Basic
  program, the condition either is true or false

48
If..Then..Else Statement

• If...Then...Else Statement
• Conditionally executes a group of statements,
  depending on the value of an expression.
• If condition Then
• statements
• ElseIf elseifcondition Then
• elseifstatements
• Else
• elsestatements
• End If
• -or-
• If condition Then statements Else
  elsestatements
• Anything in brackets ( ) is optional

49
Relational Operators used to create expressions
(conditions)
50
Comparing Strings

• A string value comparison compares each character
  in two strings, starting with the first character
  in each string ( using ordinal values in the
  Unicode Character Set )

If the strings are not the same size, the shorter
string is padded on the right with spaces to make
it the same length. Note spaces come earlier
in the collating sequence than do letters and
numbers.
51
Comparing Different Data Types

• Every type of data available in Visual Basic can
  be compared
• Different numeric types can be compared to each
  other numerically
• A single string character can be compared to a
  Char data type using ordinal values
• If comparing a string to a character literal and
  option strict is on, you must use the type
  character C.a is a String, aC is a Char

52
Using the IfThenElse Statement
53
Using the IfThenElseIf Statement
54
Nested If Statements
55
Nested If Statements
56
Matching If, Else, and End If Entries

• If statements must be fully contained within the
  outer If statement
• Place the correct statements with the correct If
  and Else statements within the nested If
  statement
• This illustration shows incorrect logic( this
  is a LOGIC error, not a SYNTAX error )

57
Testing the Status of a RadioButton Object in Code
Checked is a Boolean variable. You do not need
to writeIf Me.radPine.Checked True then
58
Block-Level Scope

• Scope is defined by where the variable is
  declared within a program
• Within an event handler, an IfThenElse
  statement is considered a block of code
• Variables can be declared within a block of code
• The variable can be referenced only within the
  block of code where it is declared

59
Using Logical Operators

• When more than one condition is included in an
  If...Then...Else statement, the conditions are
  called a compound condition

60
Using the And Logical Operator
61
Using the Or Logical Operator
62
Using the Not Logical Operator
63
Other Logical Operators
AndAlso / OrElse do short-circuit boolean
evaluation
64
Order of Operations for Logical Operators
65
Using the Not Logical Operator
66
Select Case Statement

• In some programming applications, different
  operations can occur based upon the value in a
  single field

67
Select Case Statement

• Select...Case Statement (Visual Basic)
• Runs one of several groups of statements,
  depending on the value of an expression.
• Select  Case  testexpression
•  Case expressionlist
•  statements 
•  Case Else
•  elsestatements 
• End Select

68
Select Case Statement
69
Select Case Test Expressions
70
Using Relational Operators in a Select Case
Statement
71
Using Ranges in Select Case Statements
72
Selecting Which Decision Structure to Use

• You might be faced with determining if you should
  use the Select Case statement or the
  If...Then...ElseIf statement to solve a problem
• Generally, the Select Case statement is most
  useful when more than two or three values must be
  tested for a given variable
• The If...Then...ElseIf statement is more flexible
• More than one variable can be used in the
  comparison
• Compound conditions with the And, Or, and Not
  logical operators can be used

73
Code Snippets

• Right-click the line in the code editing window
  where you want to insert the snippet
• Click Insert Snippet on the shortcut menu
• Double-click Common Code Patterns, which is a
  folder that contains commonly used code such as
  the If...Then...Else statement
• Double-click the Conditionals and Loops folder
  because an If...Then...Else statement is a
  conditional statement
• Double-click the If...Else...End If Statement
  code snippet

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Code Snippets
75
Validating Data

• Developers should anticipate that users will
  enter invalid data
• Developers must write code that will prevent the
  invalid data from being used in the program to
  produce invalid output
• Visual Basic Language Reference
• IsNumeric Function (Visual Basic)
• Returns a Boolean value indicating whether
  an expression can be evaluated as a number.
• Public Function IsNumeric(ByVal Expression As
  Object) As Boolean

76
Testing Input to Determine If the Value Is
Numeric

• The Visual Basic IsNumeric function can check the
  input value to determine if the value can be
  converted into a numeric value such as an Integer
  or Decimal data type

77
Checking for a Positive Number
78
Deploying the Application

• With Visual Studio open and the program you want
  to run loaded, click the Start Debugging button
  on the Standard toolbar
• If necessary, select USA Windows Mobile 5.0
  Pocket PC R2 Emulator in the Device list. Click
  the Deploy button

79
Deploying the Application
80
Using the Input Panel

• When you use the emulator, you can enter data
  directly from the keyboard
• The Pocket PC has the input panel to enter data
  into applications
• You can use a stylus to select the characters
  from the input panel.
• When you press the stylus on a character in the
  input panel, the character is entered into the
  focused object on the form

81
Closing the Emulator

• When you are finished with the application, close
  the emulator by clicking the Close button (X) in
  the upper-right corner of the Pocket PC emulator
• It is critical that you click the No button

82
Summary

• Write programs for devices other than a personal
  computer
• Understand the use of handheld technology
• Write handheld applications for a Personal
  Digital Assistant
• Use the Panel object
• Place RadioButton objects in applications

83
Summary

• Display a message box
• Make decisions using IfThen statements
• Make decisions using IfThenElse statements
• Make decisions using nested If statements

84
Summary

• Make decisions using logical operators
• Make decisions using Case statements
• Insert code snippets
• Test input to ensure a value is numeric

85
CHAPTER FIVE COMPLETE

• Mobile Applications Using Decision Structures