BEngBEng Hons Electronics

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BEng/BEng (Hons)Electronics Computing

• Module EEE342M1
• Visual Programming
• Lecture 2
• Creating applications in VB -
• Working with controls

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• Lecturer Anthony McCourt
• Room MG223
• Tele 5556 (internal)
• 028 7137 5556 (external)
• E-mail a.mccourt_at_ulst.ac.uk
• Web http//www.infm.ulst.ac.uk/anthony

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Recap
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The VB Desktop
Properties window
Project window
Toolbox
Form
Pull-down menus
Tool bar
Immediate window
Form layout window
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VB Toolbox

• This is something that you must be familiar with
  since you will use the objects on the toolbox to
  draw every interface that you create. The figure
  on the next slide indicates what is available to
  you

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The Toolbox Control
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VB Toolbox

• Pointer Used to select and edit objects
• Picture box A display device which can contain
  bit-mapped pictures, text and line drawings
• Label Used to display text that the user cannot
  change
• Text box A text input device which accepts
  keyboard input and allows editing. It can format
  and display single or multiple lines of text.

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VB Toolbox

• Frame This is an object which allows other
  controls to be arranged in logical groups. It
  has no behavior on its own.
• Command button Operates like a push button,
  which is pressed by clicking the mouse on it.
• Check box Displays an on or off value. It is
  used to display or enter data that can only be
  one thing or another.

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VB Toolbox

• Option button Is usually used in a group of
  similar controls, and is used to select between a
  number of mutually exclusive options. It is also
  referred to as a radio button.
• Combo box A device that can be used to enter or
  select data. It is essentially a single text box
  attached to a list. An entry can be typed into
  the text box or an existing entry can be
  selected.
• List box Just like the list part of a combo box.

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VB Toolbox

• Horizontal Scroll bar A control which can be
  used to set a level or position of a quantity.
• Vertical Scroll bar As above
• Timer Operates by running a piece of program
  code at pre-set intervals

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Displaying the time

• Specification Display the time to the nearest
  second on a form

1. Open a new project and place two labels on the
form. Caption of left label is The time is.
Delete caption of the right label, set its name
to lblTime and its style property to 1- Fixed
Single 2. Place a timer control on the form. Set
its name to tmrTimer and its Interval property
to 1000. 3. Double click the timer to bring up
the code template for its Timer event and add
the following code,
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Time program continued

• Private Sub tmrTimer_Timer()
• lblTime.Caption Time
• display current time in the label
• End Sub

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Time program continued

• 4. Run the program. Notice you do not see the
  timer that you placed on the form but you do
  see the time ticking away to the nearest second

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VB Toolbox

• Drive List box A very specialized form of
  control which is used to select and display from
  a range of disk drives
• Directory List box Similar to the drive list
  box, but is used to display files in a specific
  directory. In general, the three file selection
  tools - Drive, Directory, and File Lists - are
  used together to allow the user to select an
  existing file from a disk, or to specify the name
  of a new file.
• File List box Use this control to display a list
  of files selected by their file attributes.

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VB Toolbox

• Shape Graphical objects, such as circles,
  rectangles and rounded boxes can be added to a
  visual basic form.
• Line Lines, like graphics, can be used to
  embellish a form.
• Image An image box is similar to a picture box,
  but has fewer events to deal with, and so is more
  efficient. Image controls are a better choice
  for displaying straight-forward bitmaps, and
  automatically stretches the bit map to fit the
  size of the control, if required.

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VB Toolbox

• Data Control Used to access databases. This
  control represents a means of linked your VB
  application to an existing database.
• OLE Stands for Object Linking Embedding. By
  adding an OLE control, you can provide the user
  with a means to access other Windows applications.

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Creating Applications

• A VB user interface consists of forms and
  objects.
• Most VB programs have at least one form.
• Objects are items that appear on a form, such as
  command buttons, scroll bars, option buttons,
  text boxes, check boxes, etc.
• An object enables your program to interact with
  the user.

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Creating Applications

• The Visual Basic Application that you create is
  composed of several components
• Project - the name for a single VB application or
  program, stored as .VBP files
• Form - a window in the application (a project can
  have multiple forms), stored as .FRM files.
  Forms contain various objects (from the Toolbox)
• Custom Controls - special VB code objects, stored
  as .VBX files
• Code Modules - programs without any graphics,
  stored as .BAS files

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Main Menu Options for Managing Projects

• Running an ApplicationThe first form in a
  project (often Form1) is called the startup form.
• Ending a ProgramThe statement that stops a
  program when it is running is just the End
  statement.
• Use the Exit caption e.g.Sub
  CommandExit_Click EndEnd Sub

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Defining Properties

• After you create a form and draw some objects on
  it, the next step is to define the properties of
  each form and object.
• An objects properties determine the objects
  general appearance on the screen.
• Different objects have different properties.
• You should always alter the properties to suit
  your current application before you start to add
  the code that makes the objects work.

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The Properties Window
Object Box - Displays the name of the object for
which you can set the properties
Properties List - The left column displays all
the properties for the selected object the right
column displays the current setting for each
property
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Naming Conventions

• Default name
• e.g. Form1, Picture1
• Change to something more meaningful descriptive
• e.g. frmShape, picMagee, txtFirstName
• Naming convention introduced by Microsoft
• Reduce confusion
• Promote standardization
• Makes maintenance easier

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Naming Conventions for VB
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• For more information on naming conventions and
  VBA Programming Standards see

Programming Standards
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Summary

• The text box is used for entering displaying
  data
• The list box combo box are used for displaying
  a list of items from which the user can select an
  item.
• Two or more option buttons allow the user to
  select an option. The Value property holds True
  if the button is selected and False otherwise

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Summary

• Any number of check boxes can be selected at the
  same time. The Value property holds 1 if the box
  is selected and 0 otherwise
• A frame is often used to hold groups of option
  buttons or check boxes
• A timer has a Timer event that is called after an
  elapse of time equivalent to its Interval
  property
• A Visual Basic function returns a value