Tutorial 11 Introduction to Visual Basic zLanguage developed for special-purpose Windows...
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Transcript of Tutorial 11 Introduction to Visual Basic zLanguage developed for special-purpose Windows...
Tutorial 1 1
Introduction to Visual Basic
Language developed for special-purpose Windows applications – 1991
Uses IDE – Integrated Development Environment
Code based on Q-BasicEvent DrivenPrebuilt graphical components
(controls)
Tutorial 1 2
Two Time Frames
Design Time – when application is being built
Run Time – when application is actually functioning
Tutorial 1 3
Steps in building a VB Application
1. Create the GUI
2. Set the properties for all controls
3. Write the code
Tutorial 1 4
1. Creating the GUI
Form – container for different components of the interface Becomes window on desktop at Run time Shows grid for aligning controls at Design
time – measured in TWIPS (1/1440 in) Graphical elements placed on Form called
Objects or Controls Controls can be added (& properties
changed) during Design & during Run times
Tutorial 1 5
Opening a Project
To open a new project, use the File menu’s New Project command.
To open an existing project, click the Open Project button on the Standard toolbar. You also can use the Open Project command on the File menu, or the Ctrl+O key combination.
Tutorial 1 6
Five windows included in the Visual Basic Startup Screen
Main
Form
Toolbox
Project Explorer (Project)
Properties
Tutorial 1 7
Visual Basic startup screen
Toolbox
Form
Tutorial 1 8
Default-size label control added to the form
Tutorial 1 9
Classes and Objects
Each tool in the toolbox represents a class, which is a pattern from which one or more objects, called controls, are created
Each control you create is an instance of the class from which it was created
Tutorial 1 10
Sizing, Moving, and Deleting Controls
You can size, move, and delete a control, as well as set its properties Before you can delete a control, the
control must be selected and the form must be the active window
Tutorial 1 11
Selecting More Than One Control
You can change a property for more than one control at a time Click the first control you want to
select, then Ctrl-Click the remaining controls
Use the mouse pointer selection method
Tutorial 1 12
2. Setting the properties
Properties – attributes of a control (size, color, caption, etc.) Properties Window Default values Form is actually a control itself with
properties
Tutorial 1 13
Project and Properties Windows
Tutorial 1 14
Caption vs Name Property
Caption property the text seen by the user
Name property assigns a name to an object used by the programmer to refer to an
object in code
Tutorial 1 15
Name Property
Must begin with a letterCan contain letters, numbers, and
the underscore character onlyMust not contain punctuation
characters or spacesMust not exceed 40 charactersUse the three-character IDs shown in
Figure 1-10 (lbl, cmd, txt, frm,…etc.)
Tutorial 1 16
3. Writing the Code
Event – action that can occur at run time
Code written in code window – can double click a control at Design time & write code or click on View Code button & select control
Event procedure – the code that tells computer what to do if an event happens
Tutorial 1 17
Open Code Window
Tutorial 1 18
Listing of Properties and Methods
Tutorial 1 19
Editor Tab in the Options Dialog Box
Tutorial 1 20
Saving a Project
Click the Save Project button on the Standard toolbar. Provide a name for the form and the project.
You also can use the Save <filename> As and Save Project As commands on the File menu. However, be sure to save the form before saving the project.
Tutorial 1 21
Starting and Ending a Project
To start a project: Click the Start button on the Standard toolbar. You also can press F5 or use the Start command on the Run menu.
To end a project: Click the End button on the Standard toolbar. You also can use the End command on the Run menu.
Tutorial 1 22
Printing an Application
Tutorial 1 23
Getting Help
Use the Help menu’s Contents, Index, or Search commands.
Click the object, window, property, and so on for which you want help, then press the F1 key.
Tutorial 1 24
MSDN Library Visual Studio 6.0
Tutorial 1 25
Caption Property’s Help Screen
Tutorial 1 26
Making an Executable File
Visual Basic’s compiler translates the application’s code into machine code
The machine code is stored in a file with a .exe extension on its name
Not in working model of VB!
Tutorial 1 27
Debugging Technique
Print the application’s properties (Form As Text) and code.
In the properties printout, look for a property that is not set correctly.
In the code printout, look for an instruction that is either in the wrong object’s Code window or in the wrong event procedure.