copyright © 2007 pearson education, inc. publishing as pearson addison-wesley slide 7- 1 starting...

Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Slide 7- 1

STARTING OUT WITH

Visual Basic 2008FOURTH EDITION

Tony GaddisHaywood Community College

Kip IrvineFlorida International University

Copyright © 2007 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

Chapter

Multiple Forms,Standard Modules,And Menus

7


Introduction

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


Multiple Forms7.1

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


Form Names Each form has Name property

Programs refer to a form by this name VB assigns name Form1 Name property allows us

to change form name Standard prefix is frm

Each form also has a file name (.vb extension) Forms are stored on disk using this name Right click in Solution Explorer, and select

Rename to change the file name


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 Change the default name Click the Add button New form now appears in:

Design window Solution Explorer


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

If you have two forms frmMain & frmError, youmay select these tabs: Error form design Error form code Main form design Main form code


Removing a Form

A form may also be removed from a project To remove a form and delete its file from disk:

Right-click on the form in Solution Explorer Click Delete on the pop-up menu

To remove a form but leave its file on disk: Right-click on the form in Solution Explorer Click Exclude from Project on the pop-up menu

Slide 7- 8


First form in a project becomes startup object Form displayed when application starts

Right-click project in Solution Explorer to change startup form Click Properties Click down arrow in

Startup Form box Select new startup

form from list Click Ok

Slide 7- 9

Changing the Startup Form


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


Creating an Instance of a Form Dim statement creates an instance of a 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 in RAM errorForm used to perform actions 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()


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()


Modeless Forms & Show Method

A modeless form allows the user to change focus at will to another form in the application while the modeless 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()


Closing a Form

A form may close itself using the Close method and referring to itself using the keyword "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


Hiding a Form

Closing a Form removes it from memory To retain the form in memory but remove it from

the display, use the Hide Method:

To redisplay a hidden form use the ShowDialog or Show method

Me.Hide()


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

More on Modal and Modeless Forms

statement;messageForm.ShowDialog()

' Statements below will not execute' until the Form is closed

statement;

statement;messageForm.Show()

' Statements below will execute‘ immediately after Form is displayed

statement;


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


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, each time focus shifts back to the form


Creating an Activated Event Handler

Slide 7- 19

Create an Activated event handler by selecting frmMain events from the class name drop-down list

Then select the Activated Event from the method name drop-down list


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 closedPrivate 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 Thene.Cancel = False ‘continue, close form

Elsee.Cancel = True ‘cancel form close

End IfEnd Sub


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 Form is already closed when event fires

Create the Closing and Closed events in the same way as the Activated event Click the class name drop-down list Select formname Events Click desired event from the method drop-down list


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 displayingDim greetingForm As New frmGreeting()greetingForm.lblMessage.Text = "Hello!"greetingForm.ShowDialog()


Class-level Variables in a Form

Class-level variables are Private by default Private variables are not accessible by code in

other forms To gain access to variables from other forms, a

variable must be declared as: Class level Public

Public sngTotal As Single' Instead of the declaration' Dim sngTotal As Single


Public/Private Procedures in a Form

Procedures, by default, are Public They can be accessed by code outside 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


Standard Modules7.2

A Standard Module Contains Code - Declarations and Procedures -

That Are Used by Other Files in a Project


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, functions, or variables used in one

form should be declared in that form Procedures, functions, or variables used by many

forms may be declared in a standard module


Standard Module Syntax

ModuleName is normally same as .vb file Module Contents are sub procedures and

functions which can be Private - used only by procedures or

functions in that module Public - can be called from anywhere in your

Visual Studio project If not specified, a procedure is public

Module ModuleName[Module Contents]

End Module


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 Add button A new empty module now appears in:

Code window Solution Explorer


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


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


Menus7.3

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


Components of a Menu System

Each drop-down menu has a menu name Each drop-down menu has a list of actions or menu

commands that can be performed Some commands may lead to a submenu


Components of a Menu System

Actions may be performed using a key or key combination called a shortcut key

A checked menu command toggles between the checked (if on) and unchecked (if off) states

A separator bar helps group similar commands


MenuStrip Control A MenuStrip control adds a menu to a form

Double-click on the MenuStrip icon in the Menus & Toolbars section of the Toolbox

The MenuStrip control is displayed in the component tray (bottom of Design window)

A MenuStrip can have many ToolStripMenuItem objects: Each represents a single menu command Name property - used by VB to identify it Text property – text displayed to the user


ToolStripMenuItem Object Names

Should begin with mnu Then by convention are named based on their

text property and position in the menu hierarchy mnuFile mnuFileSave mnuFilePrint mnuFileExit


ToolStripMenuItem Text Properties

The text property holds the menu item description that is displayed to the user

If an access key is assigned, that letter must be preceded with an ampersand

Object Name Access Key Text Property

mnuFileF &FilemnuFileSave S &Save

mnuFilePrint P &PrintmnuFileExit X E&xit


Menu Designer

The Menu Designer allows visual menu creation by filling in boxes with the menu text:

Enter firstcommand inthe File menu

Enter thenext menuname


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


Checked Menu Items

Some menu items just turn a feature on or off For example, an alarm for a clock

To create a checked menu item: Set CheckOnClick property to true Set Checked property to True if feature should

be on when the form is initially displayed Can test a checked menu item in code

If mnuSettingsAlarm.Checked = True Then

MessageBox.Show(“Wake UP!”)

End If

Slide 7- 39


Disabled Menu Items

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 enabledmnuEditPaste.Enabled = True

mnuEditPaste.Enabled = False


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


Submenus

When selecting a menu item in the designer, a Type Here box appears to the 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


Inserting, Deleting, & Rearranging

To insert a new menu item within the list Right-click the item to follow the new one Select Insert then MenuItem from pop-up 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 pop-up menu

The Menu Designer can rearrange items using a click and drag approach


ToolStripMenuItem Click Events Menus and submenus require no code Commands must have 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 menu item object mnuFileExit, then add a Me.Close command as shown below

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


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


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 ContextMenuStrip control in the ToolBox to add it to the component tray

Build menu system using Menu Designer Build Click event procedures as needed Use ContextMenuStrip property of form

controls to link desired control(s) to the menu


The High Adventure Travel Agency Price Quote Application

7.4

Build an application with multiple forms,

a standard module, and a menu system


High Adventure Travel Main Form

Slide 7- 48


High Adventure Travel Scuba Form

Slide 7- 49


High Adventure Travel Sky Diving Form

Slide 7- 50


High Adventure Travel Spelunking Form

Slide 7- 51

copyright © 2007 pearson education, inc. publishing as pearson addison-wesley slide 7- 1 starting...

Documents

form instance

startup form slide

windows form

form names

specific form

new startup form

form variable errorform

button new form