1. Microsoft Visual Basic 2008 CHAPTER FIVE Mobile Applications Using Decision Structures

2. 5 Chapter 5: Mobile Applications Using Decision Structures2 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. 5 Chapter 5: Mobile Applications Using Decision Structures3 Objectives ►Display a message box ►Make decisions using If…Then statements ►Make decisions using If…Then…Else statements ►Make decisions using nested If statements

4. 5 Chapter 5: Mobile Applications Using Decision Structures4 Objectives ►Make decisions using logical operators ►Make decisions using Case statements ►Insert code snippets ►Test input to ensure a value is numeric

5. 5 Chapter 5: Mobile Applications Using Decision Structures5 Chapter Project

6. 5 Chapter 5: Mobile Applications Using Decision Structures6 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. 5 Chapter 5: Mobile Applications Using Decision Structures7 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. 5 Chapter 5: Mobile Applications Using Decision Structures8 Create a Smart Device Application

9. 5 Chapter 5: Mobile Applications Using Decision Structures9 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. 5 Chapter 5: Mobile Applications Using Decision Structures10 Placing Objects on the PocketPC Form Object

11. 5 Chapter 5: Mobile Applications Using Decision Structures11 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 --- > pnlWoodType

12. 5 Chapter 5: Mobile Applications Using Decision Structures12 Using the Panel Object

13. 5 Chapter 5: Mobile Applications Using Decision Structures13 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. 5 Chapter 5: Mobile Applications Using Decision Structures14 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. 5 Chapter 5: Mobile Applications Using Decision Structures15 Adding the RadioButton Objects

16. 5 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 Chapter 5: Mobile Applications Using Decision Structures16

17. 5 Chapter 5: Mobile Applications Using Decision Structures17 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. 5 GroupBox versus Panel Chapter 5: Mobile Applications Using Decision Structures18

19. 5 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 Chapter 5: Mobile Applications Using Decision Structures19

20. 5 MsgBox [ Message only ] ►MsgBox( “Message” ) ►-------------------------------------------------------------- ►MsgBox(“Enter the Linear Feet of the Cabinet”) Chapter 5: Mobile Applications Using Decision Structures20

21. 5 Chapter 5: Mobile Applications Using Decision Structures21 Displaying a Message Box

22. 5 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 ) Chapter 5: Mobile Applications Using Decision Structures22

23. 5 Chapter 5: Mobile Applications Using Decision Structures23 Displaying a Message Box

24. 5 MsgBox [ with Caption and Button ] ►MsgBox( “Message”,, ”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”) Chapter 5: Mobile Applications Using Decision Structures24

25. 5 Chapter 5: Mobile Applications Using Decision Structures25 Displaying a Message Box

26. 5 MsgBoxStyle Button(s) Enumeration Chapter 5: Mobile Applications Using Decision Structures26 MsgBoxButtons Arguments ValueUsage MsgBoxStyle.OKOnly 0 Displays an OK button [default setting] MsgBoxStyle.OKCancel 1 Displayhs an OK and Ca ncel button MsgBoxStyle.AbortRetryIgnore 2 After a failing situation, the user can choose to Abort, Retry, or Ignore MsgBoxStyle.YesNoCancel 3 Displays Yes, No, and Cancel buttons MsgBoxStyle.YesNo 4 Displays Yes and No buttons MsgBoxStyle.RetryCancel 5 After an error occurs, the user can choose to Retry or Cancel

27. 5 MsgBox [ with Caption, Button, and Icon ] ►MsgBox( “Message”,, ”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”) Chapter 5: Mobile Applications Using Decision Structures27

28. 5 Displaying a Message Box Chapter 5: Mobile Applications Using Decision Structures28

29. 5 MsgBoxStyle Icon Enumeration Chapter 5: Mobile Applications Using Decision Structures29 Icon NameValueIcon PictureUsage MsgBoxStyle.Critical 16 Alerts the user to an error MsgBoxStyle.Question 32 Displays a question mark MsgBoxStyle.Exclamation 48 Alerts the user to a possible problem MsgBoxStyle.Information 64 Displays an information icon

30. 5 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 … Chapter 5: Mobile Applications Using Decision Structures30

31. 5 Chapter 5: Mobile Applications Using Decision Structures31 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. 5 Values Returned by a MessageBox [ returns a value of type DialogResult ] Chapter 5: Mobile Applications Using Decision Structures32 DialogResult Enumeration Specifies identifiers to indicate the return value of a dialog box. Member nameDescription AbortThe dialog box return value is Abort (usually sent from a button labeled Abort). CancelThe dialog box return value is Cancel (usually sent from a button labeled Cancel). IgnoreThe dialog box return value is Ignore (usually sent from a button labeled Ignore). NoThe dialog box return value is No (usually sent from a button labeled No). None Nothing is returned from the dialog box. This means that the modal dialog continues running. OKThe dialog box return value is OK (usually sent from a button labeled OK). RetryThe dialog box return value is Retry (usually sent from a button labeled Retry). YesThe dialog box return value is Yes (usually sent from a button labeled Yes).

33. 5 Chapter 5: Mobile Applications Using Decision Structures33 Displaying a Message Box [ 1 Argument ] [ The Show method takes up to 4 arguments ]

34. 5 Chapter 5: Mobile Applications Using Decision Structures34 Displaying a Message Box

35. 5 Chapter 5: Mobile Applications Using Decision Structures35 Displaying a Message Box [ 2 Arguments ]

36. 5 Chapter 5: Mobile Applications Using Decision Structures36 Displaying a Message Box

37. 5 Chapter 5: Mobile Applications Using Decision Structures37 Displaying a Message Box [ 3 Arguments ]

38. 5 Chapter 5: Mobile Applications Using Decision Structures38 Displaying a Message Box

39. 5 MessageBoxButtons Enumeration Chapter 5: Mobile Applications Using Decision Structures39 MessageBoxButtons Specifies constants defining which buttons to display on a MessageBox.MessageBox These are defined as an enumeration Member nameDescription OKThe message box contains an OK button. [ default ] OKCancelThe message box contains OK and Cancel buttons. AbortRetryIgnoreThe message box contains Abort, Retry, and Ignore buttons. YesNoCancelThe message box contains Yes, No, and Cancel buttons. YesNoThe message box contains Yes and No buttons. RetryCancelThe message box contains Retry and Cancel buttons.

40. 5 Chapter 5: Mobile Applications Using Decision Structures40 Displaying a Message Box [ 4 Arguments ]

41. 5 Displaying a Message Box Chapter 5: Mobile Applications Using Decision Structures41

42. 5 Chapter 5: Mobile Applications Using Decision Structures42 MessageBoxIcon Enumeration There is also the member name None for which no icon is displayed

43. 5 Chapter 5: Mobile Applications Using Decision Structures43 Message Box IntelliSense ►In the code editing window, inside the event handler you are coding, press CTRL+SPACEBAR. 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. 5 Chapter 5: Mobile Applications Using Decision Structures44 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. 5 Chapter 5: Mobile Applications Using Decision Structures45 Displaying a Message Box

46. 5 Chapter 5: Mobile Applications Using Decision Structures46 Displaying a Message Box [ 2 arguments ]

47. 5 Chapter 5: Mobile Applications Using Decision Structures47 Making Decisions with Conditional Statements Using an If…Then 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. 5 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 Chapter 5: Mobile Applications Using Decision Structures48

49. 5 Chapter 5: Mobile Applications Using Decision Structures49 Relational Operators [ used to create expressions (conditions) ]

50. 5 Chapter 5: Mobile Applications Using Decision Structures50 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. 5 Chapter 5: Mobile Applications Using Decision Structures51 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, “a”C is a Char…

52. 5 Using the If…Then…Else Statement Chapter 5: Mobile Applications Using Decision Structures52

53. 5 Chapter 5: Mobile Applications Using Decision Structures53 Using the If…Then…ElseIf Statement

54. 5 Nested If Statements Chapter 5: Mobile Applications Using Decision Structures54

55. 5 Nested If Statements Chapter 5: Mobile Applications Using Decision Structures55

56. 5 Chapter 5: Mobile Applications Using Decision Structures56 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. 5 Chapter 5: Mobile Applications Using Decision Structures57 Testing the Status of a RadioButton Object in Code Checked is a Boolean variable. You do not need to write: If Me.radPine.Checked = True then

58. 5 Chapter 5: Mobile Applications Using Decision Structures58 Block-Level Scope ►Scope is defined by where the variable is declared within a program ►Within an event handler, an If…Then…Else 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. 5 Chapter 5: Mobile Applications Using Decision Structures59 Using Logical Operators ►When more than one condition is included in an If...Then...Else statement, the conditions are called a compound condition

60. 5 Chapter 5: Mobile Applications Using Decision Structures60 Using the And Logical Operator

61. 5 Chapter 5: Mobile Applications Using Decision Structures61 Using the Or Logical Operator

62. 5 Chapter 5: Mobile Applications Using Decision Structures62 Using the Not Logical Operator

63. 5 Chapter 5: Mobile Applications Using Decision Structures63 Other Logical Operators AndAlso / OrElse do short-circuit boolean evaluation

64. 5 Chapter 5: Mobile Applications Using Decision Structures64 Order of Operations for Logical Operators

65. 5 Chapter 5: Mobile Applications Using Decision Structures65 Using the Not Logical Operator

66. 5 Chapter 5: Mobile Applications Using Decision Structures66 Select Case Statement ►In some programming applications, different operations can occur based upon the value in a single field

67. 5 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 Chapter 5: Mobile Applications Using Decision Structures67

68. 5 Chapter 5: Mobile Applications Using Decision Structures68 Select Case Statement

69. 5 Chapter 5: Mobile Applications Using Decision Structures69 Select Case Test Expressions

70. 5 Chapter 5: Mobile Applications Using Decision Structures70 Using Relational Operators in a Select Case Statement

71. 5 Chapter 5: Mobile Applications Using Decision Structures71 Using Ranges in Select Case Statements

72. 5 Chapter 5: Mobile Applications Using Decision Structures72 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. 5 Chapter 5: Mobile Applications Using Decision Structures73 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

74. 5 Chapter 5: Mobile Applications Using Decision Structures74 Code Snippets

75. 5 Chapter 5: Mobile Applications Using Decision Structures75 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. 5 Chapter 5: Mobile Applications Using Decision Structures76 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. 5 Chapter 5: Mobile Applications Using Decision Structures77 Checking for a Positive Number

78. 5 Chapter 5: Mobile Applications Using Decision Structures78 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. 5 Chapter 5: Mobile Applications Using Decision Structures79 Deploying the Application

80. 5 Chapter 5: Mobile Applications Using Decision Structures80 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. 5 Chapter 5: Mobile Applications Using Decision Structures81 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. 5 Chapter 5: Mobile Applications Using Decision Structures82 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. 5 Chapter 5: Mobile Applications Using Decision Structures83 Summary ►Display a message box ►Make decisions using If…Then statements ►Make decisions using If…Then…Else statements ►Make decisions using nested If statements

84. 5 Chapter 5: Mobile Applications Using Decision Structures84 Summary ►Make decisions using logical operators ►Make decisions using Case statements ►Insert code snippets ►Test input to ensure a value is numeric

85. Microsoft Visual Basic 2008 CHAPTER FIVE COMPLETE Mobile Applications Using Decision Structures