1. Multiple Forms, Standard Modules, And Menus
Chapter 7
Multiple Forms,
Standard Modules,
And Menus

2. Chapter 7 Introduction

3. Chapter 7 Topics How to add multiple forms to a project
How to create a standard module
Holds procedures and functions not associated with a specific form
Creating a menu system
Context menus
With commands and submenus that the user may select from

4. Section 7.1 Multiple Forms
Visual Basic Projects May Have Multiple Forms
A Form Designated as the Startup Object Is Displayed When the Project Executes
Other Forms in a Project Are Displayed by Programming Statements

5. Form Names Each form has its specific name
Programs refer to a form by this name
VB assigns a default name Form1 to forms
A form’s Name property allows us to set or change the form name
Standard prefix for form names is frm
Each form also has a file name (.vb extension)
Forms are stored on disk using this name
To change the file name:
Right click in Solution Explorer, select Rename

6. Adding a New Form to a Project
Click Add New Item on the toolbar
Or Project on menu, then Add Windows Form
Add New Item dialog box appears
Click on Windows Form under Templates
Change the default name if you wish
Click the Open button
New form now appears in:
Design window
Solution Explorer

7. Switching from Forms to Form Code
Design window has two tabs for each form
One for form design
One for the code associated with a form
For two forms named frmMain and frmError, can select from the following tabs:
frmMain.vb[Design] Main form design
frmMain.vb Main form code
frmError.vb[Design] Error form design
frmError.vb Error form code

8. Changing the Startup Form
First form created in a project becomes the startup object
The form displayed when application runs
To make another form the startup object
Right-click project name in Solution Explorer
Click Properties
Click down arrow in Startup Form box
Select new startup form from drop-down list
Click Ok

9. Classes and Instances The form design is a class
It’s only a design or description of a form
Think of it like a blueprint
A blueprint is a detailed description of a house
A blueprint is not a house
The form design can be used to create one or more instances of the form
Like building a house from the blueprint
In order to use a form in a program, we must first create an instance of it from the design

10. Creating an Instance of a Form
Dim statement used to create instance of form
To create an instance of frmError:
frmError is the form design name (the class)
New frmError creates an instance of the form
Variable errorForm refers to the form instance and is used to perform operations on the form
The form is not yet visible, but it now exists
Show or ShowDialog makes the form visible
Dim ObjectVariable As New ClassName()
Dim errorForm As New frmError()

11. Modal Forms & ShowDialog Method
A modal form prevents the user from changing focus to another form in the application as long as it remains open
For example:
Variable errorForm represents an instance of frmError as shown in the previous slide
The ShowDialog method displays the form instance named errorForm as a modal form
Must close errorForm in order to change focus to another form in the application
errorForm.ShowDialog()

12. Modeless Forms & Show Method
A modeless form allows the user to change focus at will to another form in the application while that form remains open
For example:
Variable errorForm represents an instance of frmError as shown previously
The Show method displays the form instance named errorForm as a modeless form
Can change focus to other forms in the application while errorForm remains open
errorForm.Show()

13. Closing a Form
A form may close itself using the Close method and referring to itself as "Me":
As in
Me.Close()
Private Sub btnClose_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) _
Handles btnClose.Click
Me.Close()
End Sub

14. Hiding a Form Closing a Form eliminates it from memory
To retain the form in memory but remove it from the display, use the Hide Method:
To redisplay the form use the ShowDialog or Show method
Me.Hide()

15. More on Modal and Modeless Forms
Display of a modal form causes execution of calling statements to halt until form is closed
Display of a modeless form allows execution to continue
Tutorial 7-1 demonstrates these differences
statement;
messageForm.ShowDialog()
' Statements below will
' not execute until the
' Form is closed
statement;
messageForm.Show()
' Statements below will
' execute right after the
' Form is displayed

16. The Form Load Event
The Load event is triggered just before the form is initially displayed
Any code needed to prepare the form prior to display should be in the Load event
If some controls should not be visible initially, set their Visible property in the Load event
Double click on a blank area of the form to set up a Load event as shown below
Private Sub frmMain_Load(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles MyBase.Load
End Sub

17. The Form Activated Event
The Activated event is triggered when focus switches to the form from another form or application
The Load event is triggered once when the form is initially displayed
The Activated event is also triggered when the form is initially displayed
Occurs immediately after the Load event
The Activated event may be triggered many more times while a form is being displayed

18. The Form Closing Event
The Closing event is triggered as the form is being closed, but before it has closed
The Closing event can be used to ask the user if they really want the form closed
Private Sub frmMain_Closing(ByVal sender As Object, _
ByVal e As System.ComponentModel.CancelEventArgs) _
Handles MyBase.Closing
If MessageBox.Show(“Are you Sure?”, “Confirm”, _
MessageBoxButtons.YesNo) = DialogResult.Yes Then
e.Cancel = False ‘continue, close form
Else
e.Cancel = True ‘cancel form close
End If
End Sub

19. The Form Closed Event Closed event triggered after a form is closed
Note that it is now too late to prevent the form from being closed (it is already)

20. Using Objects on a Different Form
When code in a form refers to an object, it is assumed that object is in that same form
You can refer to an object in another form
Simply preface the object name with the variable name associated with that form
frmGreeting has a control named lblMessage
Set Text property to Hello before displaying
Dim greetingForm As New frmGreeting()
greetingForm.lblMessage.Text = "Hello!"
greetingForm.ShowDialog()

21. Class-level Variables in a Form
Class-level variables are Private by default
This means they are not accessible by code in other forms
If you want to access from other forms, they must be declared with the Public qualifier:
Public sngTotal As Single
' Instead of the declaration
' Dim sngTotal As Single

22. Public/Private Procedures in a Form
Procedures, by default, are Public
They can be accessed by code outside of their Form
To make a procedure invisible outside its own form, declare it to be Private
Tutorial 7-2 provides an opportunity to work with a multiple form application

23. Section 7.2 Standard Modules
A Standard Module Contains Code - Declarations and Procedures - That Are Used by Other Files in a Project

24. Standard Modules A separate .vb file not associated with a form
Contains no Event Procedures
Used for code to be shared by multiple forms
Procedures or variables used by one form should be declared in that form
Procedures or variables used by many forms should be declared in a standard module

25. Standard Module Syntax
Module ModuleName
[Module Contents]
End Module
ModuleName is normally same as .vb file
Module Contents are sub procedures and functions which can be
Private - only used by functions in that module
Public - can be called from outside of the module
If not specified, a procedure is public

26. Adding a Standard Module
Click Add New Item on the toolbar
Or Project on menu, then Add Module
Add New Item dialog box appears
Click on Module under Templates
Change the default name if you choose
Click the Open button
A new empty module now appears in:
Code window
Solution Explorer

27. Module Level Variables
These are declared within a module
But outside of any functions or sub procedures in that module
If declared Dim or Private, the scope is the module (called module scope)
If declared Public, the scope is the entire application (called global scope)
Tutorial 7-3 demonstrates the use of a standard module in an application

28. Application with No Startup Form
Must change the startup form to Sub Main
Main must be a public sub procedure
It must be in a standard module
When the application starts
No Form will be displayed
Main will be given control

29. You Use the Menu Designer to Create a Menu System
Section 7.3 Menus
Visual Basic Allows You to Create a System of Drop-down Menus for Any Form in Your Application
You Use the Menu Designer to Create a Menu System

30. Components of a Menu System
Menu Name
Menu Command
Submenu
Each drop-down menu has a menu name
Each drop-down menu has a list of actions or commands that can be performed
Some commands may lead to a submenu

31. Components of a Menu System
Shortcut Key (F7)
Access Key (L)
Commands can be performed by
A key or key combination called a shortcut key
A single letter and the Alt key called an access key
Menu must be open to use an access key
Shortcut key works when menu is not displayed

32. Components of a Menu System
Checked Menu Command
Separator Bar
A disabled menu command can’t be selected at present and shows as a light color (grayed out)
A checked menu command toggles between the checked (if on) and unchecked (if off) states
A separator bar helps group similar commands

33. MainMenu Control
Add to form with double-click on MainMenu control in Toolbox Menus & Toolbars section
The MainMenu control is displayed in the component tray (bottom of Design window)
May have many MenuItem objects with the following key properties:
MenuItem name used by VB to identify it
MenuItem text displayed to the user
Actions in the form of a MenuItem click event
Submenu
Separator bar

34. MenuItem Object Names Should begin with mnu
Then by convention are spelled, specifying their hierarchical position:
mnuFile
mnuFileSave
mnuFilePrint

35. MenuItem Text Properties
The text property holds the item description displayed to the user
If an access key is assigned, that letter must be preceded with an ampersand
Object Name Text Property Access Key mnuFile &File F mnuFileSave &Save S mnuFileExit E&xit X

36. Menu Designer
The Menu Designer allows menu creation by filling in a box with the menu text:
Enter the
next menu
name
Enter first
command in
the File menu

37. Shortcut Keys
Keyboard based shortcuts that execute menu commands without using the menu system
For example, ctrl-c to Copy to the clipboard
These are set via the Shortcut property of each menu item
A shortcut is displayed to the user only if the ShowShortcut property is set to true

38. Disabled MenuItem Objects
A menu item is grayed out (disabled) with the Enabled property
Paste option is initially disabled and only enabled after something is cut or copied
Code initially disables the Paste option
Following a cut or copy, Paste is enabled
mnuEditPaste.Enabled = False
mnuEditPaste.Enabled = True

39. Adding Separator Bars Right-click menu item, select Insert Separator
Separator inserted above the menu item
Or create a menu item with one hyphen (-) as the text property

40. Submenus
When selecting a menu item in the designer, a Type Here box appears to its right
Begin a submenu by setting up this menu item
If a menu item has a submenu, a solid right-pointing arrow will be shown for this item

41. Inserting, Deleting, & Rearranging
To insert a new menu item within the list
Right-click the item to follow the new one
Choose Insert New from the shortcut menu
Use Menu Designer to add new menu items at the end by entering the text to appear
To remove a menu item
Right-click on the item
Choose Delete from the shortcut menu
The Menu Designer can rearrange items using a click and drag approach

42. MenuItem Click Event Procedures
Menus and submenus require no code
Commands require a click event procedure
Double click on the menu item
Event procedure created in the code window
Programmer supplies the code to execute
Double click the MenuItem object named mnuFileExit to create the following
Private Sub mnuFileExit_Click(ByVal sender as System.Object, _
ByVal e as System.EventArgs) Handles mnuFileExit.Click
Me.Close()
End Sub
Programmer supplied code
Click event procedure created by VB

43. Standard Menu Items
In general follow the conventions that most application menu systems use
File is leftmost item with access key Alt-F
File item has Exit command, access key Alt-X
Help is the rightmost item
Help menu has an About command
Tutorial 7-4 demonstrates how to create a menu system

44. Context Menus A pop-up menu that appears on a right-click
Context menus are designed for a particular control or set of controls
To set up a Context Menu:
Double-click ContextMenu control in the ToolBox to add it to the component tray
Build menu system using Menu Designer
Build Click event procedures as needed
Use ContextMenu property of form controls to link desired control(s) to the menu

45. Section 7.4 The High Adventure Travel Agency Price Quote Application
Build an application with multiple forms, a standard module, and a menu system