CSCI 3131.01 Chapter 7 Multiple Forms, Standard Modules and Menus Instructor: Bindra Shrestha University of Houston

1. CSCI 3131.01 Chapter 7 Multiple Forms, Standard Modules and Menus Instructor: Bindra Shrestha University of Houston – Clear Lake Fall 2010

2. Acknowledgement Dr. Xinhua Chen And Starting Out with Visual Basic 2010 by Tony Gaddis and Kip Irvine

3. Topics Multiple Forms Standard Modules Menus

4. 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

5. Form Names • Each form has Name property • Programs refer to a form by this name • VB assigns name Form1 • Name property allows usto 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

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 • Change the default name • Click the Add 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 • If you have two forms frmMain & frmError, youmay select these tabs: • Error form design • Error form code • Main form design • Main form code

8. 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

9. Changing the Startup Form • 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 inStartup Form box • Select new startup form from list • Click Ok

10. 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

11. 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) • NewfrmError 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()

12. 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()

13. 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()

14. 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

15. 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()

16. 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 statements messageForm.ShowDialog() ' Statements below will not execute ' until the Form is closed statements statements messageForm.Show() ' Statements below will execute ' immediately after Form is displayed statements

17. 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

18. 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

19. Creating an Activated Event Handler • 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

20. 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

21. 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 desiredevent from the method drop-down list

22. 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()

23. 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

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, 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

25. Syntax of Standard Module Module ModuleName [Module Contents] End Module • 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

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 Add 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. 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

30. 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

31. 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

32. 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

33. 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 NameAccess KeyText PropertymnuFile F &FilemnuFileSave S &Save mnuFilePrint P &PrintmnuFileExit X E&xit

34. Menu Designer • The Menu Designer allows visual menu creation by filling in boxes with the menu text: Enter the next menu name Enter first command in the File menu

35. 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

36. 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 Then • MessageBox.Show("Wake Up!") End If

37. 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 enabled mnuEditPaste.Enabled = False mnuEditPaste.Enabled = True

38. 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

39. 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

40. 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

41. 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

42. 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

43. 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