Using Menus, Common Dialogs, Procedures, Functions, and Arrays

1
Chapter 7

• Using Menus, Common Dialogs, Procedures,
  Functions, and Arrays

2
Objectives

• Understand menu bar, menus, shortcut menu,
• Understand the StatusBar, the PictureBox
  controls,
• Use one-dimensional and multidimensional arrays
  in code
• Passing arguments to functions and procedures.

3
Know You Dog Quiz

• The application displays a picture of a specific
  dog breed which the user must identify. User may
  navigate to the first, last, previous, or next
  question. To pass the quiz, the user must answer
  all questions correctly.

4
InterfaceDesign
5
Interface Design

• A shortcut menu provides users with an easily
  accessible menu of commands, given the context of
  the application
• A ContextMenu control is used to add the shortcut
  menu to the form
• Use a common dialog box when a shortcut is used
• A PictureBox control displays the image in
  different formats.
• A StatusBar control anchors to the bottom of the
  form, displays status information.

6
Array

• An Array holds many values. It provides a way to
  give several variables a common name and use an
  index to access each item.
• Examples
• Solution(1) 1 Solution(2) 4
• QuestionChoice(1,1) English Springer Spaniel
• QuestionChoice(1,2) Akita
• QuestionChoice(1,3) Husky

7
Arrays

• Allows programmers to represent many values with
  one variable name
• Elements in the array are distinguished by their
  subscript
• The lower-bound of a subscript is 0

For intNumber 0 To 11 dblTotal
dblMonth(intNumber) Next intNumber
8
The Dim Statement for Arrays

• Dynamic dimension A variable or expression for
  upper-bound value
• Dim intValues(intUpperBound) As Integer

9
Declaring Arrays

• The program uses gshrAnswer array to track the
  users answers.
• All values of array are initialized to -1
• If the user licks the second RadioButton, the
  corresponding element receives a value of 1

10
Declaring Arrays

• The solution to the quiz questions is stored in
  gshrSolution array, and compared to gshrAnswers
  array.
• An element with a value of 0 indicates that the
  correct answer should be the answer displayed on
  the first RadioButton control.

11
Indexes

• Elements in an array are referenced in code by
  their index

12
Multidimensional Arrays

• VB. Net allows arrays to have up to 32
  dimensions.
• Dim dblCost(2, 4) As Double

13
Multidimensional Arrays
Dim intTime() as Short _ 13, 30, 5, 17,
12, 45, _ 34, 26, 16, 26, 23, 35,
IntSum2 0 IntSum4 0 For intModel 0 TO 4
intSum2 intTime(intModel, 1) Next
intModel For intMachine 0 TO 5 intSum3
intTime(3, intMachine) Next intMachine
14
Declaring a Two-Dimensional Array

• Quiz has seven questions, each of which has four
  answer choices and one image file
• We use an array of 7 by 5.
• Each question is represented by a row, with each
  answer choice represented by a column
• The image file name is represented by the last
  column

15
Array Methods

• You may use several array methods to retrieve
  information about an array

16
Sub Procedures

• A sub procedure is a unit of code that executes
  when called from code in other procedures
• Unlike function procedures, sub procedures do not
  return values
• Like functions, sub procedures accept variables,
  constants and expressions as arguments

17
Function Procedures

• Performs tasks and returns a value back to the
  code that called it
• Similar to VB.NETs intrinsic functions

18
Returning a Value by a Function

• You return a value from a function procedure to
  the line of code that called it by
• Setting the function name to a value within the
  function before exiting.
• Using the return statement

19
Function QuizResult()

• The QuizResult() function returns True if the
  user answers all of the questions correctly.

20
Exit Menu Command and FontDialog Control

• Click the Form1.vb tab in the main work area.
  Double-click the Exit command on the File menu of
  the Form1 form and type line 345 in the code
  window
• Double-click the Font command on the Options
  menu, and type lines 349 through 355

21
Passing Arguments Between Procedures

• Passing By Value method
• ByVal keyword
• Passes the value of the variable (default method)
• CalculateTax((dblIncome),intTaxBracket)
• Passing By Reference method
• ByRef keyword
• Passes the memory location of the variable
• Allows you to modify the variable in procedure
• Private Sub CalculateTax(ByRef dblValue As Double)

22
Coding a Sub Procedure

• A sub procedure DisplayQuestion() displays a
  question to user and checks the radio buttons for
  the answer

23
Coding a Sub Procedure

• The value of the radAnswer1.Checked property is
  compared with True.