Las Vegas, Nevada, December 3 6, Kevin Vandecar. Speaker Name:

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1 Las Vegas, Nevada, December 3 6, 2002 Speaker Name: Kevin Vandecar Course Title: Introduction to Visual Basic Course ID: CP11-3 Session Overview: Introduction to Visual Basic programming is a beginning programming course. It will cover basic programming constructs and show you how to make efficient use of the Interactive Developer Environment (IDE) and other tools. We will cover topics pertaining to VB and touch on the area of ActiveX Automation to show how to use VB to drive other products such as AutoCAD, Inventor, and Autodesk Architectural Desktop.

2 VB What is it? Visual Basic What s the difference between VB and VBA? VBA IDE Form Designer Project Toolbox Properties Form Layout Components References Object Browser HELP VBA IDE 2 Visual Basic Code Editor Auto complete Syntax errors Navigating Book marks Splitter Automatic pop-up List box for properties, methods, constants, etc. 2

3 Lab VB IDE Create a simple form and explore the Visual Basic IDE characteristics. 1. Start Visual Basic From the New Project Dialog (that should display automatically), notice the different types of VB projects that can be created. 3. Choose Standard EXE 4. Display the Toolbox if it s not already displayed (from the View Menu pick Toolbox) 5. Select the CommandButton Object 6. Draw a button onto the default Form 7. Display the Properties Windows if it is not already displayed (from the View menu pick Properties Window) 8. Select the Form (not the button) by single clicking. Notice the Form properties in the Properties Window. 9. Change the Form Caption to Lab 01 (this changes the Window title) 10. Select the Button by single clicking it. Notice the the button properties in the Properties Window. 11. Change the caption to Click Me. 12. Double-Click the button. This will place you into the Code Editor and automatically create a Button handler for your button (more on this later). 13. Add the following code within the procedure: MsgBox "Hello VB World" 14. Click the Start Button from the Standard Toolbar, or from the Run menu click Start. 15. Click the Click Me button and you should have a pop-up Message Box dialog saying Hello VB World. 16. Click OK to dismiss this dialog, then dismiss the form window by clicking the X in the upper right corner. 17. Display the Project Explorer if it is not already displayed (from the View menu, select Project Explorer) 18. Right-Click on the Form1 item (you may need to expand the project tree branches) notice how you can easily switch between the code window and the form window. 19. Display the Form Layout window if it is not already displayed (from the View menu, select Form Layout) 20. Move the Form s default startup position, then run the program again to see how the startup position can be set. 21. Notice how moving the Form in the Form Layout Window changes the Top and Left properties of the form. 3

4 Programming structure VB language hierarchy Project Module Procedure» Statements Modules To Add a new module Click the insert button on the standard toolbar Right-click the project explorer Choose Insert-> Module Modules should contain: Declarations of variables, constants, and user-defined data types Compiler Options Sub Procedures, Functions, Events, Properties, or Classes Procedures Sub Function Classes Objects Can Contain both variables and functions Programming Structure Scope Public vs. Private Declarations Defines a named item Assignments Store a value in a variable Executable statements Program flow! Compiler options Tells compiler how to handle code Naming Rules must start with a letter no punctuation except for _ no spaces 255 characters max (40 for forms/controls) no VB keywords no duplicates within scope 4

5 variable names ignore case Conventions What about Application specific types/objects? Formatting Code Indenting Automatic indenting Changing tabs Blank lines Spaces Line continuation _ Comments Variables An ID for a storage location Declaration Where Scope Why When Static Multiples in same statement DO: Dim a As Integer, b As Integer NO: Dim a, b As Integer Data types Boolean Byte Integer 16 bit number Long 32 bit number Single Single precision floating point value (32-bit) Double double precision floating point value (64 bit) Data types Currency Decimal 112 bits / 14 bytes (huge!) Date Object VBA object reference String Variant - 22 bytes can be a huge storage overhead User-defined Const never changes 5

6 Lab 02 Program Structure Create a new Function of type Double which takes two double arguments. Return the multiplication of the two input values to the caller. Create a new sub procedure to call the function and pass two double values. Test subprocudure. Use msgbox to output returned answer. In all code follow naming convention rules. Also make sure code formatting is correct. Pay attention to how VB automatically formats code. 1. In the code you created for Lab 01, rename the caption for the Button to Program Structure. 2. Within the Code window add a new function by typing the following code immediately above the existing procedure (place the entire statement on a single line): Function Multiply(dblA As Double, dblb As Double) As Double 3. After you press enter, if the code was typed correctly, the End Function code will automatically be added for you. 4. Within the function block, add the following code: Multiply = dbla * dblb 5. By assigning the function name to the calculation, it acts like a return of a value to the caller (in many other languages you would simply return a * b). Your new function should now appear as follows: Function Multiply(dblA As Double, dblb As Double) As Double Multiply = dbla * dblb End Function 6. Now we need to call the function with some arguments. Withing the existing procedure (the button handler that has the MsgBox code), add the following variable declaration: Dim dblresult As Double 7. Now add code to actually call the function and receive the result: dblresult = Multiply(10, 5) 8. Finally output the result to the user by changing the old MsgBox call to be: MsgBox dblresult The Updated Procedure should now appear something like: 6

7 Private Sub Command1_Click() Dim dblresult As Double dblresult = Multiply(10, 5) MsgBox dblresult End Sub 9. Run the code and make sure you get the correct value. You can change the values to ensure the code is working. 7

8 Operators Precedence ^ - *,/ \ Mod +,- String Concatenation: & Comparison: =,<>,<,>,<=,>=,Like,Is Logical: Not, And, Or, Xor,Eqv,Imp Program Flow Conditional Branch If then Select Case Conditional Loops Do loop For Next For Each Next Bad Idea GoTo 8

9 Lab 03 Program Flow Write a function that accepts an integer and returns a color string. It should use If then elseif logic for 3 colors and handle unknown values. 1=red, 2=blue, 3=yellow. Write a Sub Procedure to call the function and print the return value in a msgbox. 1. Add a new button to your existing code. Change the caption for the button to be IF LOGIC. 2. Double click the button to create a new handler procedure. 3. Create a new function immediately above this new handler procedure by adding the following code: Function getcolor(intindex As Integer) As String If (intindex = 1) Then getcolor = "RED" ElseIf (inindex = 2) Then getcolor = "BLUE" ElseIf (intindex = 3) Then getcolor = "YELLOW" Else getcolor = "UNKNOWN" End If End Function 4. Add code in the procedure handler to test this new function. For example: Private Sub Command2_Click() MsgBox getcolor(1) MsgBox getcolor(3) MsgBox getcolor(10) End Sub 5. Test the code. 9

10 Write a new function that does the same as the function above, only use a select case conditional logic. Test with a new sub procedure. 1. Add a new button to your existing code. Change the caption for the button to be CASE LOGIC. 2. Double click the button to create a new handler procedure. 3. Create a new function immediately above this new handler procedure by adding the following code: Function getcolor2(intindex As Integer) As String Select Case intindex Case 1 getcolor2 = "RED" Case 2 getcolor2 = "BLUE" Case 3 getcolor2 = "YELLOW" Case Else getcolor2 = "UNKNOWN" End Select End Function 4. Add code in the procedure handler to test this new function. For example: Private Sub Command3_Click() MsgBox getcolor2(1) MsgBox getcolor2(3) MsgBox getcolor2(10) End Sub 5. Test the code. Write a procedure to exercise loop logic. 1. Add a new button to your existing code. Change the caption for the button to be LOOP LOGIC. 2. Double click the button to create a new handler procedure. 3. Add the following for-loop code: Dim i As Integer Dim intresult As Integer For i = 0 To 5 intresult = intresult + i Next MsgBox intresult 4. Test your code. Play with different values. Try one of the other loop structures (examples can be found in the help). 10

11 Arrays An Array is simply a variable that references multiple values through an indexing system Single Dimension Multiple Dimension Dynamic Collections A Collection is simply a variable that allows access to a set of values or objects Can store any type of value or object Must be created with New 11

12 Lab 04 Arrays and Collections Load a two dimensional array with doubles. The dimensions should be 10,3. Output the array values by using a nested for each statement. 1. Add a new button to your existing code. Change the caption for the button to be STATIC ARRAYS. 2. Double click the button to create a new handler procedure. 3. Add the following array code to populate the array: Dim dblpts(10, 3) As Double Dim i As Integer, j As Integer For i = 1 To 10 If i = 1 Then dblpts(i, 1) = 1.2 dblpts(i, 2) = 2.4 dblpts(i, 3) = 3.6 Else dblpts(i, 1) = 1.2 * dblpts(i - 1, 1) dblpts(i, 2) = 2.4 * dblpts(i - 1, 1) dblpts(i, 3) = 3.6 * dblpts(i - 1, 1) End If Next i 4. Add the following array code to access the array: For i = 1 To 10 For j = 1 To 3 Debug.Print i & "," & j & " " & dblpts(i, j) Next j Next i 5. Test the code. Notice how this code uses an if structure within a for-loop to populate the array. After the array is loaded, then we can access it by referencing a specific index within the array. This example also shows the use of the Debug.Print method which will output the values to the Immediate window rather than needing a MsgBox. This makes it easy to provide a lot of output without having to respond to a message box. Create a dynamic array and redimension it twice. Cut the end off and notice the loss of data! 1. Add a new button to your existing code. Change the caption for the button to be DYNAMIC ARRAYS. 2. Double click the button to create a new handler procedure. 12

13 3. Add the following array code to populate the array and then access the array with only three items: Debug.Print "Start Run" Dim arraytest() As String Dim i As Integer ReDim arraytest(3) For i = 1 To 3 arraytest(i) = "Number = " & i Next i For i = 1 To 3 Debug.Print arraytest(i) Next i 4. Add the following array code to resize the dynamic array to now hold six items, add some additional items, and then access the whole array again: ReDim Preserve arraytest(6) ' Must use Preserve! For i = 4 To 6 arraytest(i) = "Number = " & i Next i For i = 1 To 6 Debug.Print arraytest(i) Next i 5. Add the following array code to truncate the dynamic array to now hold only five items, and then try to access the array again (including the truncated item; test your code): ReDim Preserve arraytest(5) ' Looses last value For i = 1 To 6 'error is generated when we try and 'access the last value that was truncated! Debug.Print arraytest(i) Next i Debug.Print "End Run" 6. Fix the code so that it doesn t generate the error. 7. Test the Code again. 13

14 Built-in VB Functions, Statements, and Methods VBA as a language provides built-in functionality that can be easily used. Math Formatting Conditional Math Abs Function Atn Function Cos Function Formatting Allows value formatting based on region settings Format FormatNumber FormatDateTime FormatCurrency FormatPercent IIf Short form If statement Hex and Octal &O = Octal value follows &H = Hexadecimal value follows Conversion CBool,CByte,CCur,CDate,CDbl,CDec,CInt, CLng,CSng,CStr,CVar based on reginal settings Str based on US standards Val back to string Chr ASCII values to character Asc ASCII values from character Text Manipulation Filter Join Left Len Lcase LSet Ltrim Mid Replace Exp Function Fix Function Int Function 14

15 Lab 05 Built-ins Write a function to accept a low and high number. Use these numbers to find a random number in between and return the random number to calling sub procedure. 1. Add a new button to your existing code. Change the caption for the button to be BUILT-INS-TEST. 2. Double click the button to create a new handler procedure. 3. Add a new function to calculate the random number: Function funcrand(intupper As Integer, intlower As Integer) As Integer funcrand = Int((intUpper - intlower + 1) * Rnd + intlower) End Function 4. Add code in the button handler procedure to execute the function with a range of : MsgBox funcrand(50, 100) 5. Test the code. Note that we used two built-in functions to handle the calculation. The first was the Int function that wil remove the fractional part of a number. The second function Rnd, generates the random number. Write a simple sub procedure that exercises some date and time formatting functions. 1. Add a new button to your existing code. Change the caption for the button to be BUILT-INS- FORMATDATE. 2. Double click the button to create a new handler procedure. 3. Add the following code to format the raw date value: Debug.Print "Start Run" Dim dateval As Date dateval = #12/25/2001 1:58:24 AM# ' Santa's visit from last year Debug.Print Format(dateVal, "General Date") Debug.Print Format(dateVal, "Medium Date") Debug.Print Format(dateVal, "Short Date") Debug.Print FormatDateTime(dateVal, vblongtime) Debug.Print "End Run" 4. Test the code. Note that the formatting functions took a raw date value and was easily able to extract just portions that might be needed for certain tasks. 15

16 Write a simple sub procedure that exercises some various number formatting functions. 1. Add a new button to your existing code. Change the caption for the button to be BUILT-INS- FORMATNUMBER. 2. Double click the button to create a new handler procedure. 3. Add the following code to exercise number formatting: Debug.Print "Start Run" Dim flt As Single flt = Debug.Print Format(flt, "General Number") Debug.Print Format(flt, "Currency") Debug.Print Format(flt, "Fixed") Debug.Print Format(flt, "Percent") Debug.Print Format(flt, "Scientific") Debug.Print FormatNumber(flt, 1) Debug.Print FormatCurrency(flt, 2) Debug.Print "End Run" 4. Test the code. Write a simple sub procedure that exercises the IIf built-in function. 1. Add a new button to your existing code. Change the caption for the button to be BUILT-INS-IIF. 2. Double click the button to create a new handler procedure. 3. Add the following code to exercise IIf: Debug.Print IIf(Format(Now, "a/p") = "a", "AM", "PM") 4. Test the code. Note that we used three built-ins to determine and output whether the current time is AM or PM. The Now function returns the Date, the Format used in this manner returns whether it s a (for AM) or p (for PM). Then we use the IIf function to match the return value and Print either AM (when the value is a, or PM (when the value is p ). 16

17 UI -- Simple Interactions MsgBox InputBox UI -- Forms Forms and Controls are objects and must be programmed Plan the Form before hand and try to plan functionality up front. Use the Form Toolbox to design the form. Select the Control to add, then draw it on the form Double-Click the control to add a control handler Forms Controls Label TextBox ComboBox ListBox CheckBox OptionButton (Radio Button) ToggleButton Labels and Text Boxes Labels used mostly for labels to TextBoxes, but can also be handy for messages to the user, etc. TextBox (aka Edit Box) is used for entering alpha-numeric data ListBoxes ListBox ComboBox Buttons and Check Boxes Check Boxes work independently of each other Radio Buttons work together. CommandButtons trigger an action when pushed Tab Strip A TabStrip is a control that contains a collection of one or more tabs. Each Tab of a TabStrip is a separate object that users can select. Visually, a TabStrip also includes a client area that all the tabs in the TabStrip share. 17

18 MultiPage MultiPage = A MultiPage is a control that contains a collection of one or more pages. Each Page of a MultiPage is a form that contains its own controls, and as such, can have a unique layout. MultiPage vs. TabStrip? If you use a single layout for data, use a TabStrip and map each set of data to its own Tab. If you need several layouts for data, use a MultiPage and assign each layout to its own Page. Unlike a Page of a MultiPage, the client region of a TabStrip is not a separate form, but a portion of the form that contains the TabStrip. The border of a TabStrip defines a region of the form that you can associate with the tabs. When you place a control in the client region of a TabStrip, you are adding a control to the form that contains the TabStrip. Scroll Bar Control A ScrollBar is a stand-alone control you can place on a form. It is visually like the scroll bar you see in certain objects such as a ListBox or the drop-down portion of a ComboBox. However, unlike the scroll bars in these examples, the stand-alone ScrollBar is not an integral part of any other control. To use the ScrollBar to set or read the value of another control, you must write code for the ScrollBar's events and methods. For example, to use the ScrollBar to update the value of a TextBox, you can write code that reads the Value property of the ScrollBar and then sets the Value property of the TextBox. SpinButton Control Clicking a SpinButton changes only the value of the SpinButton. You can write code that uses the SpinButton to update the displayed value of another control. For example, you can use a SpinButton to change the month, the day, or the year shown on a date. To display a value updated by a SpinButton, you must assign the value of the SpinButton to the displayed portion of a control, such as the Caption property of a Label or the Text property of a TextBox. To create a horizontal or vertical SpinButton, drag the sizing handles of the SpinButton horizontally or vertically on the form. ActiveX Controls Tools, References Shows on the Form Designer Create like any other control Accessing Windows APIs from VB The Windows API procedures are available to most Windows applications. These procedures allow you to expand the capabilities of your application. 18

19 Lab 06 Forms We have already been working with forms and buttons, but now let s expand it a little more. We will start a new project with a new form. Then we will add two edit boxes and a button. The user will enter two numbers in the edit boxes and then when the button is pressed we will calculate the division of the two numbers and display the output in a static text control. First let s setup the form layout. 1. Save any changes to the existing project. 2. From the File Menu, choose New Project and select a standard EXE. 3. On the new form, add two TextBox controls, each with a Label control. (see the dialog image below for an example layout). 4. Change the caption on each label to be First Number and Second Number. 5. For the first TextBox, change its name property to be txtboxnumber1 and for the second TextBox, change its name property to be txtboxnumber2. 6. For each TextBox make its Text property contain Add a new button and change its name property to be btncalc. Make the caption value be Calculate. 8. Add a Label control and change its name to be lblresult and the Caption to read Result =. 9. At this point, the form layout should resemble this image: Now let s add some handling code to perform the calculation. 1. Double click the Calculate button to create the button handler procedure. 2. Add the following code to access the textbox values and store into variables: Dim dbl1 As Double Dim dbl2 As Double dbl1 = txtboxnumber1.text dbl2 = txtboxnumber2.text 3. Add the following code to perform the calculation and store the value into a new variable: Dim dblresult As Double dblresult = dbl1 * dbl2 19

20 4. Add the following code to display the result in the Result Label: lblresult.caption = "Result = " & dblresult 5. Test your code with different values. Note that this sample is very simple. In more complex problems, you will be accessing the controls from a variety of procedures. This is why it is important to name the controls adequately so that it doesn t get confusing between the time you design the layout and when you try accessing the controls on the form. Debugging Syntax errors are easy The VBA compiler will complain Runtime errors will be shown at runtime. Logic Errors are harder Use Break Points Lab 07 Debugging Now let s take a look at debugging concepts. Understanding debugging is essential to writing error free code. 1. Within the previous lab s button handler procedure (probably named btncalc_click() ), right-click on the following line of code: dblresult = dbl1 * dbl2 2. From this context menu, select Toggle, Breakpoint. 3. Run the code and press the Calculate button. The debugger will kick in and flip the code window forward. You can now step through the code line-by-line. 20

21 Object Oriented Programming An Object is simply a definition that contains the properties and action that the object can perform or handle. For Example and AutoCAD Circle is an Object It contains Properties and Methods that are dervied from parent objects (such as AcadEntity) and also things that are specific such as center point and radius Autodesk products provide interfaces to Objects through ActiveX Automation ActiveX Automation COM, OLE, and all other names MS comes up with! ActiveX uses COM to communicate Registry Autodesk ActiveX Automation Support 21

22 Lab 08 Active X Automation Finally, let s make the form we already created, add an AutoCAD entity through ActiveX Automation. First, we need a reference to the AutoCAD type library. 1. From the Project menu, select References. 2. Select AutoCAD 2000 Object Library. 3. Select OK 4. From the View menu, select Object Browser. 5. In the Project/Library pull-down list, select AutoCAD. 6. Browse the AutoCAD Type library. Now, we can add some code to deal with AutoCAD through ActiveX Automation (out-of-process) communication. If we were using VBA, then we would be using the same Active Automation interfaces, but in an in-process state. This code will use the calculation from the previous lab to create a circle at 0,0,0 with a radius of the calculated value. 1. Open the code window for the button handler procedure used in the previous lab. 2. At the end of the existing code, add the following code to get access to the AutoCAD application object: Dim acad As AcadApplication Set acad = GetObject(, "AutoCAD.Application") Note that this code assumes that AutoCAD is already running. 3. Add the code to setup a fixed center point for the circle: Dim ctrpnt(0 To 2) As Double ' Define the circle center as 0,0,0 ctrpnt(0) = 0#: ctrpnt(1) = 0#: ctrpnt(2) = 0# 4. Add the code to create the circle in Model Space and then to zoom extents: acad.activedocument.modelspace.addcircle ctrpnt, dblresult acad.zoomextents 5. Test the code. Make sure to startup AutoCAD before executing the code. Try different values. 22