From the Main Menu select Teaching Technologies. At the login prompt enter your Teaching Theater login and password. Teaching Theater Attach window will appear listing a number of application. However, in order to run Visual Basic you need to invoke File Manager application.

Visual Basic application ver 4. is on drive K under \General\VB40.16.

Login to the NT machines using your WAM account. Then, click on Network Neighborhood. Select NetWare or Compatible Network and then Theater1or TTClass. It will ask for login and password, use your Teaching Theater login and password. The Visual Basic applications versions 3, 4, and 5 are all in the Apps\General in directories VB, VB40.16, and VB50 respectively.

1. Using VB development environment

2. Form design

1. Input / Output

 

MsgBox function basically displays a message in a dialog box and waits for the user to choose a button. The MsgBox function returns a value indicating which button the user has chosen.

 

In the below example it is used to display a simple message:

 

Sub Form_Load ()

MsgBox "Hello World!"

 

End Sub

 



 

Here in this example, Form_Load function basically executes all the statements on form load. In practice, you make initializations in this function.

 

Lets work on a more complex example. In this example we are going to use other parameters of the MsgBox function to create more than one button on the message dialog.

 

Private Sub Form_Load()

Dim I As Integer

 

I = MsgBox("Hello World!", vbOKCancel)

 

End Sub

 



 

But how can we know which button the user has pressed and take appropriate action ?

 

Private Sub Form_Load()

Dim I As Integer

 

I = MsgBox("Hello World!", vbOKCancel)

 

If I = vbOK Then

MsgBox ("OK Pressed")

End If

End Sub

 

In these examples, MsgBox function is used to display only a message. In order to capture user input in the form of text we need to use InputBox function.

 

Lets work on a simple example.

 

Private Sub Form_Load()

Dim T As String

 

T = InputBox("Your Name?")

 

MsgBox ("Hi " + T)

End Sub

 

Basically in this example a dialog is shown, with a text input box. When either of the buttons are pressed, the input text is captured and displayed in a message box.

 



 

2. Event processing

 

Visual basic uses an event-driven architecture. For example, whenever the user clicks one of the mouse buttons, or types in a key on the keyboard, a signal called an event is created. The Windows system then checks event details such as event location, where the mouse click has occurred etc. and then notifies the appropriate widget to take appropriate action.

 

Let's consider an example. Basically, let's create a simple button called MyButton and write the code that will be executed when the button is clicked. The code below simply changes the caption of the button, when the button is clicked.

 

Private Sub Mybutton_Click()

Mybutton.Caption = "Ouchh!"

End Sub

 



 

There are a number of event that we can use, for example, double-click, mouse move, mouse up and down events, got focus and lost focus events, key up and down events, drag and drop events, and many others.

 

Lets work on another example. In this example a text input box (NameIn) is shown and changes in the input box are reflected on a label item (NameOut).

 

Private Sub NameIn_Change()

NameOut.Caption = "Your name is " + NameIn.Text

 

End Sub

 



 

Let's work on a drag and drop event. In this example, three label items are created with captions as DC, MD, and VA. Dragging and dropping each item on the text item below copies the contents of the label item onto the text item.

 

Private Sub NameIn1_DragDrop(Source As Control, X As Single, Y As Single)

NameIn2.Text = Source.Caption

 

End Sub

 



 

What could go wrong here ? Simply we are assuming that the dropped object is a label. What if it is a text item would it work ? No simply because the contents a text item is stored in the Text property rather than in the Caption property as it is for the label item. The correct code should check first the type of the dragged item as follows:

 

Private Sub NameIn2_DragDrop(Source As Control, X As Single, Y As Single)

If TypeOf Source Is TextBox Then

NameIn2.Text = Source.Text

ElseIf TypeOf Source Is Label Then

NameIn2.Text = Source.Caption

End If

 

End Sub

 



 

3. Data types

 

 

 

Users can also define compound data types:

 

 

Type CustRecord

Name as string

Address1 as String

Address2 as String

City as String

State as String

Zip as String

Balance as Currency

End Type

 

Once defined, variables of this type can be declared and used as follows:

 

Dim ACustomer as CustRecord

 

ACustomer.Name = "Eser Kandogan"

ACustomer.Balance = 10000

 

 

Another data type is the Collection. A collection is basically an ordered set of items that can be referenced as one unit. There are three methods to add, remove, and reference items in a collection, Add, Remove, and Item, respectively. For example,

 

Dim Employees as New Collection

 

Employees.Add(item := "Eser")

Employees.Add(item := "Ben", before := 0)

 

Employees.Remove 4

 

MsgBox(Employees(2))

 

Object Browser is a handy utility for viewing data structures. It can be invoked from the View menu under Object Browser.

 

4. Arrays

 

Public Items(19) As Integer 'A global array of 20 integers

Private Items(49) As String 'A local array of 50 strings

Private Items(10 To 20) As Integer

Dim Algebra(1 To 20, 1 To 20) As String 'A 2-D Array of strings

 

Items(3)

 

Dynamic Arrays

 

Dim Items() As String

ReDim Items(20)

 

ReDim Preserve Items(Ubound(Items) + 10)

 

Private Function GetElement(ByRef Items() As Integer)

X = Items(3)

End Function

 

5. Program flow

 

If statement

 

If condition Then

Statements

Statements

End If

 

If condition1 Then

Statements

ElseIf condition2 Then

Statements

Else

Statements

End If

 

Select statement

 

Select Case testexpression

Case expression1

Statements

Case expression2

Statements

…

Case Else

Statements

End Select

 

Do While Loop

 

Do While condition

Statements

Loop

 

Do Until condition

Statements

Loop

 

For Next Loop

 

For counter=start To end [Step increment]

Statements

Next

 

For Each element In group

Statements

Next element

 

 

 

 

 

 

 

GoTo

 

GoTo End

End:

'I will never use GoTo

 

6. Using standard controls

 

ListBox

 

Private Sub AddButton_Click()

Call ItemList.AddItem(TextItem.Text)

 

End Sub

 

Private Sub DeleteButton_Click()

Call ItemList.RemoveItem(ItemList.ListIndex)

 

End Sub

 



 

What could go wrong here ? In Delete if none of the items is selected, the program will crash. In order to avoid that we need to check the index number.

 

Private Sub DeleteButton_Click()

If ItemList.ListIndex <> -1 Then

Call ItemList.RemoveItem(ItemList.ListIndex)

End If

 

End Sub

 

How can we include replace ?

 

Private Sub ReplaceButton_Click()

If ItemList.ListIndex <> -1 Then

Call ItemList.AddItem(TextItem.Text, ItemList.ListIndex)

Call ItemList.RemoveItem(ItemList.ListIndex)

End If

End Sub

Timer

 

Private Sub Timer1_Timer()

Static A As Integer

 

A = A Mod 8

Line1.X1 = A * 100

Line1.Refresh

 

A = A + 1

 

End Sub

 



 

 

7. File Input / Output

1. Alarm clock (Due Feb 26)

 

Design only a single mockup dialog for an alarm clock, which allows users to set an alarm by time and days of the week. The design should display the current time and date. Be creative! No coding is required.

 

2. Calendar manager (Due March 12)

• Create a directory in your account on Teaching Theaters named PROJ2
• Copy all VB files in that directory.
• Make sure it works in that directory as well.

• Create a directory in your account on Teaching Theaters named PROJ1 under Homework.
• Copy all VB files in that directory.
• Make sure it works in that directory as well.