1 / 42

Chapter 3 Introduction to Visual Basic Environment

Chapter 3 Introduction to Visual Basic Environment. A Visual Basic Application. Application – another name for a program. Interface – is what appears on the screen when the application is running. Program Code – is instructions that tells an application’s objects how to behave.

jovan
Download Presentation

Chapter 3 Introduction to Visual Basic Environment

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 3Introduction to Visual Basic Environment

  2. A Visual Basic Application • Application – another name for a program. • Interface – is what appears on the screen when the application is running. • Program Code – is instructions that tells an application’s objects how to behave. • Object Oriented Programming - Uses classes, which are program code and data, to create objects. • Objects- can have visual representation such as a dialog box, button, Label etc. • Event-driven program – when a program runs due to an object being selected by the user.

  3. The Visual Basic IDE • IDE – Integrated Development Environment. • Used to create a Visual Basic application • The Visual Basic IDE consists of: • Menu Bar • Tool Bar • Tool Box • Project Window • Project Explorer Window • Properties Window • Form Layout Window

  4. The Visual Basic IDE

  5. Visual Basic Environment • Menu Bar • Tool Bar • Project Window • Project Explorer Window • Properties Window • Form Layout Window

  6. Adding Objects to a Form • Form – is a container object for other objects

  7. Design Time • Objects are added during design time • The time during which the applications interface is being created. • Label object is used to display information. • Command Button object is something a user can click on. • Objects are added by clicking and moving your mouse over to the screen and dragging it across the form.

  8. Object Property Values • Properties – defines its appearance, behavior, position, and other attributes. • Each type of objects have many different types of properties.

  9. Label Properties • Name – identifies an object all names should start with the prefix “lbl”. • Caption – changes the text displayed in the label • Font – used to change font style, and size. • Alignment – Changes the alignment of text in a label’s caption (left & right justify and center)

  10. Command Button Properties • Name – identifies the object. Prefix “cmd”. Cannot be change at runtime. • Caption – Changes the text displayed in the command button. • Example: cmdCancelorDone.Caption = “Done”. Form Properties • Name – identifies an object. Prefix “frm”. Cannot change during runtime. • Caption – changes the text displayed in the title bar. • Example: frmUserApp.Caption = “My Application”

  11. Programming Style • When naming an object, it should start with the appropriate prefix and then be descriptive of the object’s purpose.

  12. Resizing and Moving Objects • Selecting an object is done by simply clicking on it. • Resizing by using the drag handle • Marquee Selection – Selecting the pointer control and create a dash box around several objects at one time.

  13. Saving a Project • File menu and select the “Save Project” command or clicking on disk icon shortcut key. • First saved – both form and project must be given descriptive names. • Save the form using the same name as its Name Property and then save the project using a descriptive name of the application.

  14. Running a Visual Basic Application • F5 – start command • Run Menu and select run • Run icon on the toolbar Run Time • Refers to the time during which application is being executed. • A VB program can be run at any time of its development.

  15. End Command • Run Menu – select “End” command. • Click the End icon on the Tool Bar.

  16. Application • Also refer to as Program • Contains set of instructions that tells the computer how to perform specific task. • Each line of code is referred to as a statement. Event Procedures • Is a block of code that executes in response to an event. • Event (User Event) – is a way in which the user can interact with an object, such as clicking a button. • Specific actions will be taken when the user clicks on the button.

  17. Form Module • Container for program code. • Code Editor – is the area displaying the form module View Code button View Object button

  18. Code Editor Window • Display by double-clicking on the form. • Display by clicking on the View Code Button in the Project Explorer. • Clicking the button beside the view code button returns you back to the form.

  19. Unload Statement • Removes a form from memory and ends the application. • Unload statement requires a form name to be unloaded. • If the form to be unloaded is the current form, then you could use Me • Example: • Unload Me or Unload Form1

  20. Examples of Unload Statement

  21. Adding Event Procedures • Select object name from Object list and then a corresponding event is selected from the Event name.

  22. Private • Indicates that the procedure cannot be accessed outside of the form module. • Sub declares the procedures • End Sub – ends the Sub statement. • Body is between Sub and End Sub statements.

  23. Printing A Project • The interface and program code of an application are printed by selecting the print command from the file menu • CTRL + P Removing a Project from the IDE • File menu – Select the Remove Project command.

  24. Using Assignment to Change Property Values • Assignment – is used to change the value of an object property at run time. • Assignment Statement changes property values using the equal sign (=). • Each Object property can only be assigned a valid property values.

  25. AutoList • Is displayed when typing an object’s name and a dot operator notation mark.

  26. Valid Values of the label object properties • Name – Cannot be change during run time by an assignment statement • Caption – Text in double Quote • lblMessage.Caption = “Adios” • Font – has several Subproperties • Size – 0 – 2048 • Example: lblMessage.Font.Size = 10 • Bold & Italic are True or False • Example: lblMessage.Font.Bold = True • Name – enclosed in double quote • lblMessage.Font.Name = “Arial” • Alignment – 0 – left, 1 – right, 2 – center

  27. The Form_Load Event Procedure • Event procedures can also be written for form events. • The Form_Load event procedure is executed when the form is loaded into memory.(Application is started or run) • Examples Private Sub Form_Load() lblSample.Caption = “This text is centered.” lblSample.Alignment = 2 End Sub

  28. Form_Load • Changing object property values in the Form_Load event procedure is alternative to setting property values in the Properties window. • Initializing the form – Setting object properties through the Form_Load event.

  29. Commenting Code • Comments – are used to explain and clarify program code for a human reader. • No effect on how the application runs. • Single quotation mark (‘) begins a comment • Mark code that is ambiguous or misleading. • Example: lblSample.Alignment = 0 ‘left justify • All programs should state the following: • ‘ Author: Your Name • ‘ Date: Current Date • ‘ Chapter and Exercises

  30. Opening a Project • File menu – Open Project • CTRL + O • Open Project Button on the Tool Bar

  31. Graphics • Makes programs more interesting • Makes it easier to interact with.

  32. Image Control • Located in the Tool Box • Used to create Images

  33. Properties of an Image • Name – Use the img prefix when naming and image. • Picture – is used to display a dialog box for selecting the graphic to display in the image area. • Stretch – True or False – True if it has been resized. False otherwise. • Visible – True or False – To display at run time Visible = True. To hide Visible = False.

  34. Image Object • Displays as a box, when added to a form.

  35. Selecting an Image • Go to Property box and select Picture. Click on box on ellipsis. • Stretch should be set to true so image will fit in the image box. Click event • Is when the user clicks on an image object to perform an action.

  36. Operators and Expressions • Built-in arithmetic operators • “^” - exponential • “*” - multiplication • “/” – division • “\” – Integer division • “Mod” - Modulus • “+” - addition • “-” - subtraction

  37. Expression • Arithmetic operators are used to form expressions. • Expression can be anywhere a numeric value is allowed • Example: lblAnswer.Caption = 3.14 * 10^2 • Expressions are NOT enclosed in quotes.

  38. Order of Precedence • Exponentiation • Multiplication and Division Left to Right • Addition and Subtraction Left to Right • You can change order of precedence by using parentheses.

  39. Programming Style • Always use parentheses when any ambiguity or maybe questions about the expression.

  40. Compiler & Interpreter • Visual Basic also has a compiler that translate the program code into separate executable file. • Executable file can be run on any Computer that uses Windows 95 or later. • Visual Basic acts as an interpreter that reads each line of program code as it is entered. • Visual Basic will highlight any errors immediately. • Interpreter executes the code line-by-line and displays the output in the IDE.

  41. Exiting Visual Basic • ALT + Q • File menu – Exit

  42. Visual Basic Programming Guidelines • Create the program interface first • Name all objects before writing and code. • Use Object list in Code Editor window to select the object event procedure.

More Related