Visual Basic: Week 5

1
Visual Basic Week 5

• Review
• User defined functions
• Busy wait versus Timers
• Homework read chapter 4. Acquire images for
  cards. Will work on Memory in class.

2
Review

• Visual Basic development includes
• Placing controls on the form
• Textbox, label, command button, list box, image
  control
• Control arrays of any type control
• Writing code for event procedures
• Form_Load, command button Click, list box Click

3
Code

• Assignment statements
• target expression
• If/Then/Else
• Select Case
• For/Next

4
Built-in functions

• Int
• Randomize, Rnd
• Str
• Val
• Format

5
Event procedures

• Also known as event handlers
• Visual Basic defines them.
• Defines the header.
• Visual Basic invokes them when an event happens.
• You write the code to do somethingwhat you want
  to happen when a specific event occurs.
• You write the code in the code window, which you
  get to by double clicking on the specific
  control.

6
Controls

• Each control type has its own set of properties
• All control types have (name)
• Many have position properties
• Left, Top
• Form, command button and Label have Caption
• Textbox has Text (can be changed by player)
• Command button (also Timer) has Enabled.
• Many have Visible.
• Image has Picture.
• Properties can be changed at Design time and by
  code during Run time.

7
Control array event procedure

• Suppose lblCards is an array of label controls
• The event procedure for clicking on any of the
  elements of the control array is
• Sub lblCards_Click(Index as Integer)
• Where Index will hold the index for the specific
  element clicked. You use Index in your code.
  For example, you will use this in Memory.

8
Creating a User-Defined Procedure

• A user defined procedure is one in which you
  define (author) the header as well as write the
  code.
• User defined procedures can be functions or
  subroutines, meaning they can return values or
  not.
• Call setupcards
• If hittarget(x,y) then
• You write the user defined procedure in the code
  window.