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Project 7
Creating ActiveX Controls and
Distributing Applications

Introduction

• In previous projects, CommonDialog control and DataBound ComboBox control ActiveX controls used
• Hundreds of these controls available from Microsoft and other venders
• VB6 allows creation of ActiveX controls which can be complied as (.ocx )files for future use in any application (control creation capability was first present in version 5 of Visual Basic)

Introduction

• In this project will create ActiveX StopWatch control
• In creating control will learn about Timer control and Resize event and how to create your own properties for controls
• Incorporate StopWatch control in the Multiplication Quiz application
• Learn about random numbers, and several new properties of Command buttons

Introduction

• Compile Multiplication Quiz application into an .EXE file
• Use Visual Basic Package and Deployment Wizard to create an installation program for distributing the application on floppy disks
• Use ActiveX Document Migration Wizard to create a version of Multiplication Quiz application that can be hosted by Microsoft Internet Explorer

Multiplication Quiz

• Five multiplication problems generated randomly and the timer begins
• Color of answer boxes changes to indicate correct and incorrect answers
• Start and Stop buttons contain graphic images and display ToolTip text

Creating ActiveX Controls

• ActiveX controls - are standardized user interface elements you assemble to create an application
• Temporally add an additional project to the desktop to test the design and run time behavior of your control
• Compile control into an .ocx file for use in other projects

3 Ways to Create Controls

1. Create control from scratch
2. Modify a single existing control
3. Assemble a new control from several existing controls

In this project, assemble a StopWatch control from existing Label, CommandButtons, and Timer controls

Creating a User Control Interface

• An ActiveX control created with VB is always composed of UserControl object, plus any controls placed on the UserControl, called constituent controls
• UserControl objects have code modules and visual designers like forms
• Add constituent controls to UserControl object’s Designer window, same way controls are added to forms

StopWatch Control

• StWatch control consists of five constituent controls - three CommandButtons controls, one Label control, and one Timer control

see (Figure 7- 13 VB 7.11)

• Timer control - is visible during design time but is not visible at run time

Timer Control

• Timer control used to update the display of elapsed time
• Timer control has only one event - the Timer event
• Timer event occurs when a preset interval for a Timer control has elapsed
• interval’s frequency stored in the control’s Interval property, specifies length of time in milliseconds

Timer Control

• Interval property can set number of milliseconds between 1 and 65,535 between calls
• Enabled property - determines whether or not the control responds to the passage of time
• set Enabled to False to turn a Timer control off and to True to turn it on

Timer Control

• When Timer control enabled, its countdown always starts from the value of its Interval property setting. When it reaches the end of the countdown, it executes whatever code you have added to the Timer event procedure
• In StWatch control, will start and stop Timer by changing value of Enabled property through code statements in CommandButton Click events

Writing UserControl Event Procedures

• TotalSeconds variable - used in StWatch control to keep track of elapsed seconds from Timer start to Timer stop
• declared in general declaration section to extend its scope to module level (used in Timer1_Timer and Command3_Click events)

Resize Event

• Resize event - occurs when a form or a UserControl first is displayed and when the size changes
• When StWatch control added to form or borders dragged, its constituent controls should adjust their sizes and positions automatically
• each of controls is a different size, but constituent controls always have the same relative size and position (table 7-3 VB 7.15)

Timer Operations

• Timer1_Timer event will execute every one second when its Enabled property is True
• The integer number minutes of elapsed time is calculated using the integer division operator ( \ )
      Minutes = Format ( TotalSeconds \ 60, "00")

• The Mod operator is used to divide two numbers and return only the remainder
      Seconds = Format ( TotalSeconds Mod 60, "00")

Writing UserControl Property Procedures

• Every ActiveX control has a default set of properties and values that display in Properties list
• Also have access to all properties of its constituent controls
• When ActiveX control is added to a project, can access only the properties of UserControl. No longer can access the properties of the constituent controls directly

Writing UserControl Property Procedures

• The way to access the internal behavior of the UserControl’s constituent controls is to create new properties at the UserControl level and then use changes in those properties to activate changes in properties of constituent controls
• Write code to accomplish this in Property procedures

Property Procedures

• Property procedures allow you to execute code when a property value is set or retrieved
  • can use to create own properties
• Typical property made up of pair of Property procedures
• Property Get procedure - retrieves value of a property
• Property Let procedure - assigns a value to a property

StWatch Control
(2 additional properties)

1. Buttons property - gives the user a choice of whether or not the 3 command buttons in StWatch are visible

• value of Buttons property is Boolean (True/False)
• these values map directly to the True/False values of the Visible property of the three command buttons

StWatch1.Buttons = False (will change Visible property of 3 constituent CommandButtons to False)

StWatch Control
(2 additional properties continued)

• If a user decides to make Buttons property False, then a way is required to start, stop, and reset StWatch control through code.

2. Action property - values of 1(Start), 2(Stop), or 3(Reset) will change the Value property of the corresponding CommandButton control to True using code

Properties or Methods ?

• Action property seems more like a method than a property
• In Project 2 used ShowColor method of CommonDialog control but action property could also have been used

CommonDialog1.ShowColor
CommonDialog1.Action = 3

• earlier versions of VB Show methods did not exist
• Implementation as a property or method is sometimes ambiguous and even arbitrary

WriteProperties Event

• WriteProperties event of UserControl occurs when an instance of an object is to be saved
• event signals to object that state of object needs to be saved, so it can be restored later

example - Borderstyle property of label set to 1-Fixed Single, when application closed and reopened property maintained

WriteProperties Method
( 3 arguments)

1. String expression - represents data value to be placed in property bag
2. Data value to save in property bag
3. Default value for data

Call PropBag.WriteProperty ("Caption",Label1.Caption,"Label 1")

WriteProperty method of PropertyBag object used to write a value of property

ReadProperties Event

• ReadProperties event - occurs when loading an old instance of an object that has a saved state
• ReadProperty method of the PropertyBag object is used to read a value for a property
• A PropertyBag object is passed into an object through the ReadProperties event

ReadProperties Method
(2 arguments)

1. String expression representing a data value in the property bag
2. Value to be returned if no value is present in the property bag

Label1.Caption = PropBag.ReadProperty ("Caption", "Label 1")

PropertyChanged Method

• PropertyChanged method notifies the object’s container (form) that a property’s value has been changed. By notifying the container that a property’s value has changed, the container can update the Property window with the new values of the object’s properties. This method notifies the container to activate the WriteProperties event to store the new value of the property.
• Properties available only at run time (Action property) do not need to call the PropertyChanged method

Saving ActiveX Project

• UserControls stored in plain text files containing source code and property values of UserControl and its constituent controls
• VB uses .ctl extension for source files
• If UserControl or its constituent controls use graphical elements, which cannot be stored as plain text, such as bitmaps, VB stores those elements in a .ctx file with same name as .ctl file (similar to .frx files to store graphical elements of forms)
• ActiveX project stored in project file (.vbp)

Adding Multiple Projects

• Version 5 was the first version of Visual Basic that allowed you to have multiple projects open in the Visual Basic IDE at the same time.
• Allows you to open a new Standard EXE project for testing your ActiveX control, while your ActiveX project is still open
• Can test and debug the StWatch control before it is compiled as an .ocx file

Compiling ActiveX Control

• Can add a .ctl file to Standard EXE project and control will be added to Toolbox
  • .ctl file can be used in project, if project it made into an .exe file it becomes part of the .exe file

2 Disadvantages to Above Method:

1. Newer version of control forces the project to be rebuilt
2. Every project using control would need the .ctl file in its .exe file

Solution - .ocx control available to all applications easy to replace with updated version

Multiplication Quiz Application
(Setting Properties CommandButton)

• Style property - set to 1- Graphical
• Picture property can be used to set a graphic (bitmap, icon, metafile, GIF, JPEG) to be displayed in command button
• ToolTipText property used to set text that appears as a ToolTip for the control
• ToolTip - is a word or short phrase that describes the function of a toolbar button or other button or tool

Writing Code

3 event procedures see (Table 7-8 VB 7.37)

1. Form_Resize - used to keep controls centered within application’s window when user resizes it
2. cmdStart_Click - resets answer text boxes BackColor property; generates 5 problems; reset StWatch control
3. cmdStop_Click - must stop StWatch control and grade the answers

Form_Resize Event
(Respond to 3 different states)

1. User minimizes form - do nothing
2. Not minimized and user drags width less than original - return to original width
3. User makes width greater than original (drags or maximizes) - reposition controls

Form_Resize Code

If frmMultQuiz.WindowState = 1 Then

‘do nothing

ElseIf frmMultQuiz.Width < 6780 Then

frmMultQuiz.Width = 6780 ‘user made form too small

Else ‘user made form bigger than original

Frame1.Left = (frmMultQuiz.ScaleWidth - _ Frame1.Width - 345 - 975) / 2

cmdStart.Left = Frame1.Left + Frame1.Width + 345

cmdStop.Left = Frame1.Left + Frame1.Width + 345

StWatch1.Left = Frame1.Left + Frame1.Width + 345

End If

Random Number Functions

• Random number functions - used in applications to model events whose outcome is uncertain
• Quiz - generates 5 sets of multipliers and multiplicands (integers between 0 and 9)
• Rnd function - returns a value between 0 and 1 (0 < Rnd < 1) example: .235431
• A large set of random numbers would have a uniform distribution, they are all equally likely to occur

Random Numbers Terms

• Scaling Random Numbers

Int ((upperbound - lowerbound + 1) * Rnd + lowerbound)

• Randomize statement - used to set the Seed equal to a function of the system clock to produce a different Seed each time you generate random numbers (else same sequence of random numbers generated each time)
• Seed value - starting value used by Rnd

cmdStop_Click Event

• StWatch control stopped by setting Action property equal to 2
• Although pairs of multipliers generated randomly, answer can be checked by comparing the value entered in answer text box to the product of the two numbers
• If these two match, BackColor property set to green, and red otherwise

Distributing Applications

• An .exe file may not run on other PC’s, because an .exe file requires additional files to be able to run if VB not installed
• At a minimum, an application requires the MSVBVM60.dll file, Visual Basic’s run time dll
• Other files that might be needed include ActiveX controls, data files, and dynamic link libraries (.dll)

Distributing Applications

• Cannot distribute application by copying files to floppy disk (reasons)

1. Requires more than one floppy - files must be transferred to hard drive
2. Need some way to tell user what folders to copy files to
3. If user copies .dll or .ocx file over a newer version used by another application, VB program will work but other application won’t
4. User will have to add program group and include it on the Start menu

Distributing Applications Solution

• Users expect to be able to install software by using user-friendly setup program
• Package and Deployment Wizard - uses a two step process to build setup application and distribution disks
• In the Package step it determines which files are needed and where they need to be installed on user’s machine. It bundles these files into one or more compressed cabinet (.cab) files. It creates a setup program for the user.
• In the Deploy step it writes all necessary files to distribution media selected (floppy disk, network server, Internet)

Packaging a Setup Program

• Package and Deployment Wizard - separate application run from Visual Basic group
• Package and Deployment Wizard - also available as an add-in when loaded using the Add-In Manager dialog box. A project must be saved and compiled before it can be packaged and deployed.
  • additional advanced features and options

Installing, Running, Applications

• When setup program run, decompresses files, copies them to appropriate folders after checking for newer versions, enters them into the system registry, creates program group and Start links
• It prompts user for installation information suggesting default values (folder where program files will be copied)

  Removing an Application

• When user runs setup program, an application removal utility is copied to user’s Windows folder
• also creates removal log file (which directories were created and which files were created where, any changes to system registry, and program groups, icons, and Start menu created)
• Removal utility and log file - allow user to uninstall application through Add/Remove Programs utility in Windows Control panel

  ActiveX Documents

• ActiveX containers - application used to view a document that did not create it
  • (Internet Explorer viewing Word document)
• When you open a Word document in a container such as Internet Explorer, the Word application becomes a server that supplies the objects that enable the ActiveX container to view and activate the document
  • Same mechanism works for ActiveX documents created with Visual Basic

  ActiveX Projects in VB

• When ActiveX document project created, it can be contained in an ActiveX container
• Compiling ActiveX document creates both a Visual Basic document file (.vbd extension) and its server, which can be an ActiveX .exe file
  • .vbd file is to the .doc file what the ActiveX .exe file is to the Winword.exe file
• Can create ActiveX documents from scratch or can convert existing Standard EXE projects

  Internet Distribution

• If you have a Web site, you can link to your ActiveX documents from any Web page
• Accomplished with a combination of HTML and VBScript
• Can create a link to ActiveX document that causes the browser to find and download automatically all components needed to run your ActiveX document

  Converting Projects to ActiveX Documents

• ActiveX Document Migration - process of converting Standard EXE VB projects into ActiveX documents
• ActiveX Document Migration Wizard - VB add-in that facilitates conversion
  • converts a form into ActiveX document object (file with .dob extension)
  • when existing project made an ActiveX server by making it an ActiveX.EXE file, VB also converts the document object into an ActiveX Document (.vbd ext)

  Startup Object Modifications

• In order to make an ActiveX.EXE file from an existing Standard EXE project, modifications need to be made to project’s Startup object
• There only can be one Sub Main in an application and must be created within a code module rather than a form
• Code module exists as a separate file which can be added and removed from applications like a form
• Startup object of ActiveX. EXE project must be Sub Main, even if the Sub Main procedure does not contain any code

  Project 7
  Creating ActiveX Controls and
  Distributing Applications

  END

  Use the Icon on the right to view the steps to convert an ActiveX document file to a HTML file using the Package and Deployment Wizard . This completes the process at the end of chapter 7 in your textbook on pages VB 7.63. 

  Creating and Using ActiveX Control Requirements

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