Fundamentals of Programming in Visual Basic (VB)：在Visual Basic编程基础（VB）.ppt

Fundamentals of Programming in Visual Basic (VB)
Visual Basic Events
Simple Statement
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Event
An event is an action, such as the user clicking on a button
Usually, nothing happens in a Visual Basic program until the user does something and generates an event.
What happens is determined by statements. Visual Basic Events
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Assignment Statements
Assign a value to a property.
General Form:
source = value
A value on the right-hand side of = is assigned to the left-hand size of =.
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Sample Statements
=
= True
= “Hello World”
General Form:
= setting
Value represented by setting is stored into
Color is a structure allowing us to specify various colors
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Lab
Refers to the examples in the Lab
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Sample Form
txtFirst
txtSecond
btnRed
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Focus
When you click on a text box, a cursor appears in the text box, and you can type into the text box.
Such a text box is said to have the focus.
If you click on another text box, the first text box loses the focus and the second text box receives the focus.
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Examples of Events



General Form:

This event occurs when a mouse is clicked on the button btnShow
This event occurs when user changes the text of txtBox
This event occurs when the input focus leaves txtBox
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The three steps in creating a Visual Basic program:
Create the interface; that is, generate, position, and size the objects.
Set properties; that is, configure the appearance of the objects.
Write the code that executes when events occur.
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Code Window
Method Name box
Class Name box
Page tab
Page tab:
1. is a code window
2. [design] is a design window (to manipulate the window appearance)
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