Lesson 3

1
Lesson 3 Menus, MDIs, and Simple Loops

• Microsoft Visual Basic .NET, Introduction to
  Programming

2
Objectives

• Design a menu bar with menus and submenus.
• Plan and document an application.
• Use MDI forms.
• Use For loops to write programs.

3
Vocabulary

• Access keys
• Cascade
• Definite loop
• Indefinite loop
• Loop
• MainMenu tool
• Multiple document interface (MDI)
• Separator bar
• Shortcut key
• Tile

4
Menus

• Menus are a common Windows tool that make it
  easy to access commonly used commands. It is not
  hard to imagine a Windows application with no
  menu bar all of your applications to this point
  have used buttons. Menus are a more natural
  interface than buttons because they allow you to
  group related actions. Therefore, menus are an
  important part of most Windows applications. The
  menu bar is found at the top of the application
  window directly under the title bar.
• Visual Basic lets you create menus quickly and
  easily.

5
Planning a Menu

• To what commands and options do users need
  access?
• In what order should the commands and options
  appear?
• What forms are required?
• What information needs to be included on each
  form?
• From where will this information come?
• Do the forms need to transfer information
  elsewhere?

6
Basic Elements of a Menu

• Menus are made up of the menu bar, menu titles,
  menu commands, submenu titles, and submenu
  commands.
• Menu titles appear on the menu bar at the top of
  the form. When you click a menu title, its menu
  opens and displays a list of menu commands or
  submenu titles.
• Menu items usually have associated access keys
  that allow the user to quickly access them
  through the keyboard.
• Often, menu items also have shortcut key
  combinations that let the user execute the
  command without using the mouse.

7
Basic Conventions

• Start all menu titles and menu commands with a
  capital letter.
• File and Edit are usually the first menu titles
  on a menu bar, and Help is usually the last one.
• Use short, specific captions, preferably no more
  than two words each.
• Start the names of all menu items with the
  three-letter prefix "mnu."

8
The MainMenu Tool
9
Did You Know?

• In the early days of computers, the industry
  almost died because of a lack of programmers. In
  the late 1950s and early 1960s, programmers used
  assembly language, which is the obscure code-like
  language one level above machine language, or
  binary. It quickly became apparent that if
  something did not happen to make programming
  easier, the industry was doomed. To fill this
  need, high-level languages, more easily
  understood by humans than computers, were
  developed. The computers helped themselves
  interpret these new languages.

10
Creating a Menu in a Windows Application
11
Note

• There are a number of properties of the menu
  item shown in the Properties window
• The Checked property, when True, displays a check
  mark in front of the menu item. This is often
  used to show that the menu item has already been
  selected. This property can be set to True or
  False by program code.
• The Enabled property, when False, displays the
  item grayed out, so the user cannot select it.
• The Visible property, when False, makes the menu
  item invisible to the user.
• The Text property reflects the text entered in
  the Type Here box on the form.

12
Menu Building in Progress
13
Tip

• To reorder a menu, click and drag the item to a
  new position. The other items will make room as
  you drag.

14
Access Keys

• You are probably familiar with access keys and
  shortcut keys. Access keys allow you to open a
  menu by pressing the Alt key and then the
  designated letter. Access keys also allow the
  user to access a menu command once the menu is
  open by continuing to hold the Alt key and
  pressing its designated letter.

15
Shortcuts

• Shortcut keys are different. They run a menu
  command immediately after the shortcut key
  sequence is pressed. Shortcut keys with which you
  may be familiar are CtrlC for Copy and CtrlV
  for Paste. You cannot assign a shortcut key to a
  menu title.

16
Step-by-Step 3.3

• Select the Open entry by clicking it. Click again
  to edit the entry. Position the cursor with the
  arrows and key an ampersand in front of the word
  Open. This makes the letter O the special access
  key.

17
Step-by-Step 3.3

• In the Properties window, click the Shortcut
  property. Click the list arrow to the right of
  the entry and select CtrlO from the list. This
  sets the shortcut for this menu command to
  CtrlO. With the shortcut set, the user can
  execute this command from the keyboard without
  using the mouse or the access keys to select and
  open the menu.

18
Menu Changes in Progress
19
Tip

• Remember to name your objects as you create them.
  Use short meaningful names that start with the
  correct prefix. For menu items, use the mnu
  prefix.

20
Adding Code to a Menu

• When a user clicks a menu control, a Click event
  occurs. All menu controls, with the exception of
  the separator bar, recognize the Click event.
  Coding for a menu Click event works the same as
  coding for any other event procedure. You open
  the Code window, choose the menu control from the
  Class Name box on the left, and enter the code
  between the Protected Sub and End Sub statements.
  
• Another way to open a menu items Code window is
  to double-click the menu item in the MainMenu
  tool.

21
Step-by-Step 3.4

• 'Change the color of the text in txtMenuTest to
  Black
• Dim NewColor As New Color()
• txtMenuTest.ForeColor NewColor.Black()
• 'Check the Black submenu control
• mnuEditColorBlack.Checked True
• 'Uncheck the Blue submenu control
• mnuEditColorBlue.Checked False
• 'Uncheck the Red submenu control
• mnuEditColorRed.Checked False

22
Step-by-Step 3.4

• 'Change the color of the text in txtMenuTest to
  Blue
• Dim NewColor As New Color()
• txtMenuTest.ForeColor NewColor.Blue
• 'UnCheck the Black submenu control
• mnuEditColorBlack.Checked False
• 'Check the Blue submenu control
• mnuEditColorBlue.Checked True
• 'Uncheck the Red submenu control
• mnuEditColorRed.Checked False

23
Step-by-Step 3.4

• 'Change the color of the text in txtMenuTest to
  Red
• Dim NewColor As New Color()
• txtMenuTest.ForeColor NewColor.Red
• 'Uncheck the Black submenu control
• mnuEditColorBlack.Checked False
• 'Uncheck the Blue submenu control
• mnuEditColorBlue.Checked False
• 'Check the Red submenu control
• mnuEditColorRed.Checked True

24
Running a Program

• Run the program by selecting Debug Start
  Without Debugging or pressing CtrlF5.

25
Colors

• Visual Basics handling of colors is very
  convenient for the programmer. When you click the
  list arrow in the ForeColor property in the
  Properties window, you get to choose between
  three different color management systems you may
  select a color from among System Colors, custom
  colors from a palette of colors, or one of many
  predefined Web colors.

26
Multiple Document Interface (MDI)

• The multiple document interface (MDI) is another
  common item found in Windows applications. The
  MDI allows you to create an application that has
  many forms that are contained within one main
  form. Applications like Microsoft Word, where you
  can open several different documents within the
  main Word program, are MDIs.
• The forms that make up an MDI (em-dee-eye)
  project are referred to as parent and child
  forms. The main application is referred to as the
  parent, and all of the forms contained within the
  application are called the children.

27
Parents and Children

• There can be only one MDI parent form per
  application. This cuts down on the possible
  confusion that could result from having more than
  one form in charge of the rest. You create an MDI
  parent form by setting the appropriate property
  of the form in the Properties window. When you
  create an MDI form, the Properties window refers
  to it specifically as an MDI form rather than
  just a form. To have the application recognize
  that the other forms are children of the MDI
  form, you set their MDIChild property to True.

28
Programming Skills

• A major problem that programmers run into is
  that they tend to design for their own use. It
  may seem obvious to you or another programmer how
  a program should process data and how a user
  accesses and enters that data. However, the
  end-user typically does not have the same
  perspective. Therefore, when designing a program,
  it is essential that you plan for alternate
  approaches. Murphy's law here is, If there is
  one thing that would crash a program, users will
  find it."

29
Creating an MDI Application

• In order to create an MDI application, you must
  create an MDI form. Creating an MDI form is
  similar to creating any other new form. You
  populate the form with controls from the Toolbox
  and build a menu. Then change the forms
  IsMDIContainer property to True.
• After the MDI container or parent form is
  created, you create a template from which child
  forms are created. You add a second form to the
  project and populate it with controls from the
  Toolbox and provide a menu. This second form is
  the template used to create child forms while the
  application is running.

30
Me

• While the application is running, the parent form
  can be referred to by the name Me. This is a
  special variable in Visual Basic. Me holds the
  name of the form that is currently active. Thus,
  the Me takes different values depending on the
  active form.

31
Step-by-Step 3.5

• 'Create a new instance (copy) of Form2
• Dim NewMDIChild As New Form2()
• 'Designate the Child form's parent
• NewMDIChild.MDIParent Me
• 'Display the new form.
• NewMDIChild.Show()

32
Cascaded Child Forms
33
Child Forms Tiled Horizontally
34
Child Forms Tiled Vertically
35
Child Form Icons Arranged on the Parent Form
36
Step-by-Step 3.6

• Form1.LayoutMDI(MDILayout.Cascade)
• Form1.LayoutMDI(MDILayout.TileHorizontal)
• Form1.LayoutMDI(MDILayout.TileVertical)
• Form1.LayoutMDI(MDILayout.ArrangeIcons)

37
Adding a Form

• A unique form is created in the design phase of
  the project. Even though you work with the form
  in the design phase, the form must be called into
  existence by program code. If the name of the
  added form is About.vb, the code to create a new
  instance of the form is
• Dim NewAbout As New About().

38
The New Form

• Once a new form is added, the Show method of the
  form is called to display it. The Hide method
  hides the form without unloading it from memory.
  If necessary, the forms Unload method is used to
  unload the form from memory. Unlike the child
  forms that appear wholly contained within the
  parent form, the new form is displayed
  independently.

39
Simple Loops

• Executing the same statements over and over at
  almost inconceivable speeds is what makes
  computers so powerful. Visual Basic has a number
  of statements designed to control this
  repetition.
• The first is the For loop. A loop is any program
  statement that causes the repetition of a group
  of statements. This is called a definite loop
  because its starting value, the upper limit, and
  the number of repetitions is generally known
  before the loop begins.

40
For loop

• The syntax of the For loop is
• For control variable starting value To upper
  limit Step increment
• body of the loop
• Next
• An example is
• For x 1 To 100 Step 2
• 'The statements that make up the body of the
  loop go here.
• Next x

41
Examples

• For x LowerLimit To 5 LowerLimit
• Next x
• For Item 1 to 25
• Next Item

42
Examples

• For x -5 To 5 Step 0.01
• Next x
• For Pounds 8 to 24
• Time Pounds 17
• Next Pounds

43
Backward

• Loops can count forward or backward.
• For x 10 To 1 Step -1
• Next x

44
Important

• The value of the control variable should not be
  changed in the body of a For loop. The value is
  controlled by the For loop itself.

45
Step-by-Step 3.8

• 'Declare the necessary variables.
• Dim StartingValue, UpperLimit, Increment As
  Integer
• Dim ControlVariable As Integer
• Dim DirectCost, FixedCost, TotalCost As Decimal
• 'Collect information from the TextBoxes.
• DirectCost txtDirectCost.Text.ToDecimal
• FixedCost txtFixedCost.Text.ToDecimal

46
Step-by-Step 3.8

• 'Collect information from the user.
• StartingValue CInt(InputBox("Enter the starting
  value"))
• UpperLimit CInt(InputBox("Enter the upper
  limit"))
• Increment CInt(InputBox("Enter the
  increment"))
• For ControlVariable StartingValue To UpperLimit
  Step Increment
• TotalCost DirectCost ControlVariable
  FixedCost
• MessageBox.Show("The cost at "
  ControlVariable.ToString _
• " items
  is" CrLf TotalCost.ToString)
• Next ControlVariable

47
Communication Skills

• In creating and editing programs, you will often
  forget why you did things a certain way or why a
  particular "fix" was used. That is why it is
  essential that you document your programs with
  explanations and dates for later reference. You
  may have already noticed that you have been using
  internal comments. This helps later when
  revisions are made and when the final
  documentation is done.

48
Summary

• Menus make it easier for users to execute
  commands in their programs.
• The MainMenu tool makes creating
  professional-looking menus easy.
• Shortcut keys and access keys help speed up
  access to commonly used menu commands.
• The multiple document interface is made up of one
  parent form that contains many child forms.

49
Summary

• Previously created forms can be added from other
  projects.
• The MDILayout method provides flexibility to the
  user to display child forms in different ways.
• The For statement is used to build definite loops
  that repeat statements a fixed number of times.