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Chapter 6

Chapter 6. Multiple Forms. Multiple Forms. Multiple forms Show and Hide methods for forms Standard code modules Variable scope in multiform projects An About Box form Splash screen Set the startup form. Multiple Forms. Creating new forms Adding and removing forms

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Chapter 6

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  1. Chapter 6 Multiple Forms

  2. Multiple Forms • Multiple forms • Show and Hide methods for forms • Standard code modules • Variable scope in multiform projects • An AboutBox form • Splash screen • Set the startup form

  3. Multiple Forms • Creating new forms • Adding and removing forms • Hide & Show methods • Load & Unload statements • Referring to objects in other forms • code in one form cannot “see” obj. in other forms • reference: FormName!ObjectName.property

  4. Multiple Forms • First form is startup form. • By default, it is the first one created • You can set startup form in Project, Properties • Create form: • Project, Add Form • Select form type • You can add a form to project from existing form

  5. Adding/Removing Forms • All the information in a form resides with the form: controls, properties, code, variables • Add existing form: Project, Add Form and then click the existing tab • Remove a form: Project, Remove File

  6. Hide and Show methods • You display a form with the show method: frmAbout.Show • General form is formname.Show <style> • where style can be 1 (modal) or the default value 0 (nonmodal) • User must respond to Modal form & cannot click another form in same project • Hide a form: frmAbout.Hide

  7. Form Load & Activate Events • The first time a form is displayed, it triggers a form load event followed by a form activate event • Load calls the module into memory • Activate occurs when the form receives control • Subsequently, activate but not load events trigger when form is shown

  8. Unload/Load Statements (cont'd) • Only time you might want to load a form is when you want to load a form but display it later. • The Me keyword refers, always, to the currently active form: Unload Me Me.Hide

  9. Referring to Other Forms’ Objects • You can refer to txtName in another form called frmSummary this way: frmSummary!txtName = … or frmSummary!txtName.Font.Name = ... • This implies that control names are unique within a form but need not be unique across forms.

  10. Standard Code Modules • Public procedures are“visible” to all forms • Public variables are visible to all forms • SCM (Standard Code Module) has the extension .BAS • Create SCM: Project, Add Module • DIM variables in the code module are visible to all procedures in the module, but not to procedures in the form modules.

  11. Variables & Constants in Multi-form Projects • Scope of variables: • Local: available inside a procedure • Static: inside procedure, but remembered • Module level: available anywhere in a form • Global: available across forms--anywhere • Global variables declared with Public • Variable prefix naming conventions: m for module, g for global • Scope a variable as narrowly as possible

  12. An About Box • Acts like a Windows Help|About box • Often displays information about the programmers, designers, and so on • An about box is simply a modal form with an OK button and label boxes displaying information • You can use VB’s About Dialog template

  13. A Splash Screen • Splash screen displays while product loads • Create: Project, Add Form, then select Splash Screen • Splash screen loads first instead of main form • Place splash screen load statement in Sub Main procedure in Standard Code Module

  14. Setting the Startup Form/Proc. • By default, the first form you create in a project is the startup form • You can set the startup form in the Project Properties menu (Project menu)

  15. Hands on Programming Example • Programming example is a multi-form Coffee Sales example with these forms: • Splash screen • Main form • Summary form • About box • Main form called from splash screen

  16. Programming Hints • Make form run maximized window by setting the WindowState form property to 2-Maximized • In design time, close extra windows to maximize your view of form • Clicking a form's Close button halts execution

  17. Summary (1) • Projects can have unlimited # forms • First form displayed is the startup form • You can use forms from one project in another one • Show/Hide are form methods • Modal form requires a response; and, execution halts until response received

  18. Summary (2) • Load statement loads forms but does not display them • Me refers to currently active form • Refer to object in another form with form name as prefix • SCM contains public variables and public sub procedures that are global to project

  19. Summary (3) • Public can appear only in the General Declarations section of a module—place it in Standard Code Module only by convention • Static variables are local but with “memory” • Program execution can begin in a sub procedure called Main located in Standard Code Module

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