UNIT 2 ADVANCED FEATURES OF VISUAL BASIC 6.0

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1 UNT 2 ADVANCED FEATURES OF VSUAL BASC 6.0 Structure 2.0 dentification of Some Advanced Features of Visual Basic Objectives 2.2 Employment of Features and Some More Examples Simple Animation Using ActiveX Drag and Drop Linking to Database 2.4 Summary 2.0 DENTFCATON OF SOME ADVANCED FEATURES OF VSUAL BASC 6.0 More About Visual Basic Controls Here are some detailed description of some important terms and components that you will come across. Students are advised to go through them very carefully. Forms Specifies that the coiltained controls take part in a form. t is a window or dialog box. Forms are containers for controls. A multiple-document interface (MD) form can also act as a container for child forms and some controls. Following are some of the characteristics of forms: List of Parameters Constant Value Description VbModal 1 Modal form VbModeless 0 Modeless form

2 Windows Programming using Visual Hasic 6.0 Arrange Method for MD (Multi Document nterface) Forms Constant Value Description VbCascade 0 Cascade all nonminimized MD child forms VbTileHorizontal 1 Horizontally tile all nonminimized MD child forms VbTileVertical 2 Vertically tile all ~lonminimized MD child forms VbArrangecons 3 Arrange icons for minimized MD child forms Windowstate Property Constant Value Description VbNormal 0 Normal VbMinimized 1 Minimized V bmaximized 2 Maximized Tool box Pointer mage box Text box Frame + i - General "&@, Label Check box List box Timer File list box Picture box $. d Vertical scroll Horizontal scroll +-. Directory list box Drive list box + Line LE ata control Provides a set of controls/tools from which tools can be picked and placed on the form at design time. Tool bars and Menu bars t provides quick access to commomly used commands in the programming environment. Tool bar Menu Bar

3 Project Explorer L)isplays a hierarchical list of the projects and all of the items contained in a project. Advanced Features of Visual Basic 6.0 Window Elements View Code Displays the Code window so you can write and edit code associated with the selected item. View Object Displays the Object window for the selected item, an existing form, module, ActiveX object, or user control Toggle Folders Hides and shows the object folders while still showing the individual items contained within them. List window Lists the all loaded projects and the items included in each project. Project. s The project and items contained within it are: Forms b All the.frm files associated with the project. Modules 4 All the.bas modules for the project. Class Modules All the.cls files for the project.

4 Windows Programming using Visual Rasic 6.0 User All user controls for the project. User All document objects,.dob files, in the project. Property Pages ActiveX Designers All property pages,.pag files, in the project. --m All designers,.dsr files, in the project. Related Documents Lists all documents to which you want a pointer. The path to the document is stored rather than the document itself. When you click View Object, Visual Basic searches the registry for the document type and executes the appropriate open command. You can place any valid document type in the project. Resources Lists all of the resources you have in your project. Note: A check mark to the left of a filename in the Project Explorer indicates that the file is checked out of a version control project, and currently has readlwrite status. The check mark is only displayed if you are connected to a version control program, such as Microsoft Visual Sourcesafe, which is included with the Enterprise Edition of Visual Basic. Modal and Modeless dialog boxes Dialog boxes are either modal or modeless. A modal dialog box must be closed (hidden or unloaded) before you can continue working with the rest of the application. For example, a dialog box is modal if it requires you to click OK or Cancel before you can switch to another form or dialog box. The About dialog box in Visual Basic is modal. Dialog boxes that display important messages should always be modal- that is, the user should always be required to close the dialog box or respond to its message before proceeding. Modeless dialog boxes let you shift the focus between the dialog box and another form without having to close the dialog box. You can continue to work elsewhere in the current application while the dialog box is displayed. Modeless dialog boxes are rare. From the Edit menu, the Find dialog

5 box in Visual Basic is an example of a modeless dialog box. Jse nodel less dialog boxes to display AdV""C"' Fcatures of frequently used commands or information. Visual Basic 6.0 To display a form as a modal dialog box Use the Sliow method with a style argument of vbmodal (a constant for the value 1). For example: ' Display form 1 as a modal dialog. Form 1.Show vbmodal To clisplay a form as a modeless dialog box Use the Show method without a style argument. For example: ' Display form1 as a modeless dialog. Form.Show Note: f a form is displayed as modal, the code following tlie Show method is not executed until tlie dialog box is closed. However. when a form is shown as modeless, the code following the Show method is executed immediately after tlie form is displayed. The Sliow method lias ariotlier optional argument. owner tliat can be used to specify a parent-child relationship for a form. You can pass the name of a form to this argument to make that form the owner of the new form. To clisplay a form as a child of another form Use the Show method with both style and owner arguments. For example: ' Display form 1 as a modeless child of formmain. Form 1.Show vbmodeless, formmain Using the owner argument with the Sliow method ensures tliat the dialog box will be minimized when it's parent is minimized. or unloaded should the parent form be closed. SD or MD nterface Two different styles are available for the Visual Basic DE: single document interface (SD) or multiple doculnents interface (MDT). With the SD option, all of the DE windows are free to be ~iioved anywhere on screen; as long as Visual Basic is the current application. they will remain on top of any other applications. With the MDJ option, all of the DE windows are contained within a single resizable parent window. Using the Common Dialog Control The common dialog control provides a standard set of dialog boxes for operations such as opening and saving files, setting print options, and selecting colors and fonts. The control also has the ability to display Help by running the Windows Help engine.

6 Windows Programming sing Visual Basic 6.0 The colnmon dialog control provides an interface between Visual Basic and tlie routines in tlie Microsoft Windows dynamic-link library Commdlg.dl1. To create a dialog box using this control, Commdlg.dl1 must be in your Microsoft Wi~idows \System directory. You use the common dialog control in your application by adding it to a form and setting its properties. The dialog displayed by the control is determined by the methods of tlie control. At run time, a dialog box is displayed or the Help engine is executed when the appropriate method is invoked; at design time, the common dialog control is displayed as an icon on a form. This icon can't be sized. The common dialog control allows you to display these commonly used dialog boxes: Open Save As Color Font Print To use the common dialog control 1. f you haven't already done so, add tlie common dialog control to the toolbox by selecting Components from the Project menu. Locate and select the control in the Controls tabbed dialog, then click tlie OK button. 2. On the toolbox, click the CommonDialog control and draw it on a form. When you draw a common dialog control on a form, it automatically resizes itself. Like tlie timer control. tlie common dialog control is invisible at run time. 3. At run time, use the appropriate method. as listed in the following table, to display the desired dialog. Method SliowOpen SliowSave ShowColor SliowFont ShowPrinter ShowHelp Dialog displayed Open Save As Color Font Print nvokes Windows Help i Control An ob-ject you can place on a form that has its own set of recognized properties, methods, and events. You use controls to receive user input, display output, and trigger event procedures. You can manipulate most controls using methods. Some controls are interactive (responsive to user actions), while others are static (accessible only tlirough code). 32

7 Module Code in Visual Basic is stored in modules. There are three kinds of modules: form, standard, and class. Advanced Features of Visual Basic 6.0 Simple applications can consist ofjust a single form, and all of the code in the application resides in that form module. As your applications get larger and more sophisticated, you add additional forms. Eventually you might find that there is common code you want to execute in several forms. You don't want to duplicate the code in both forms, so you create a separate module containing a procedure that implements the common code. This separate module should be a standard module. Over time, you can build up a library of modules containing shared procedures. Each standard, class, and form module can contain: Declarations. You can place constant, type, variable, and dynamic-link library (DLL) procedure declarations at the module level of form, class or standard modules. Procedures. A Sub, Function, or Property procedure contains pieces of code that can be executed as a unit. These are discussed in the section "Procedures" later in this chapter. Form Modules Form modules (.FRM file name extension) are the foundation of most Visual Basic applications. They can contain procedures that handle events, general procedures, and form-level declarations of variables, constants, types, and external procedures. f you were to look at a form module in a text editor, you would also see descriptions of tlie form and its controls, including their property settings. The code that you write in a form ~rlodule is specific to the particular application to which the form belongs; it might also reference other forrns or objects within that application. Standard Modules Standard modules (.BAS file name extension) are containers for procedures and declarations commonly accessed by other modules within the application. They can contain global (available to the whole application) or module-level declarations of variables, constants, types, external procedures, and global procedures. 'The code that you write in a standard module isn't necessarily tied to a particular application; if you're careful not to reference forms or controls by name, a standard module can be reused in many different applications. Class Modules Class rnodules (.CLS file name extension) are the foundation of object-oriented programming in! Visual Basic. You can write code in class modules to create new objects. These new objects can include your own customized properties and methods. Actually, forms are just class modules that can have controls placed on them and can display form windows. i For More nformation For information about writing code in class modules, see "Programming with Objects." Note: The Professional and Enterprise editions of Visual Basic also include ActiveX Documents, ActiveX Designers, and User Controls. These introduce new types of modules with different file name extensions. From the standpoint of writing code, these modules should be considered the same as form modules.

8 Windows Programming 2.1 sing Visual Basic 6.0 OBJECTVES After going through this unit, you will be able to: Discuss the advanced features involved in Visual basic; Develop the applications using some animation techniques; Link a database to the application. 2.2 EMPLOYMENT OF FEATURES AND SOME MORE EXAMPLES Simple Animation Using ActiveX Let us learn an important feature of Windows Programming i.e., Application 1: Program for implementing a small animation clip in an application. Step 1. Start with a normal standard exe project as shown below:

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10 Windows Programming using Visual Basic 6.0 Press 'apply' button and you will get 2 new controls in the toolbox the 'up-down control' and the 'animation control' as shown below: Step 4. Now add this control to your form just by clicking over the animation icon in the toolbox and drawing a rectangle by dragging the mouse on the form. And you will get an image of the control as shown in the figure below:

11 -r : Step 5. Similarly include two command buttons in the form as shown below: Advanced Features of Visual Basic 6.0 "' 't f, _ *, 8,. :$ * 35,q i Z $,. '6 Step 6. And now, change the caption of button1 and button2 as 'play' and 'stop' respectively, as :; shown below: i :i,';

12 Windows Programming using Visual Step 7. Now add another component 'common dialog control' in your project which is used to open some common dialog boxes as open, save as and print etc. Step 8. Now add this new component to the form as shown below:

13 Step 9. Now double click on the comlnalid button1 to move to the code window and write down the following code that is written in the click event of the comlnand button 1 as sllown below: ;\clvanced Feat~~res of Vis~~al Basic 6.0 i.comondialogl.filter = "*.AVm Co~monDialoyl. ShowOpen Anlmationl. Open ComonDialogl. FlleJ~une Animationl.Play Form1 <f%rml) Step 10. Now write the code in the click event of the command button2 as shown below: 4 CommonD~alogl. ShowOpen 1 1,-' ' r Fglrrns

14 Windows Proerammlne usini Visual Ba C Step. Now run the program and you will get the following screen: Now, when you press the play Button you'll get the following screen Arrouuhit Arrowrnis Baskt Btttvn9 Blowup Choose any AV format file and press open. And you will get the same loaded form with a new running animation file which you have choosen. To stop the aninimation you can press the stop button. And close the application bypressing the close button of the form.

15 2.2.2 Drag and Drop Let us move on one step further with an important utility of windows programming muvccu Features of Visual Basic 6.0 Application 2: Create an application, that copies a file from one location to any other location by simulating windows explorer (i.e. implementing drag and drop feature). Stepl. Load VB with a standard exe option and you will get the following screen. Step 2. Now, click the DragListBox control from the toolbox as shown in the figure:

16 Windows Programming using Visual Basic 6.0 Note: The control you have just now included in your form is having a name1'drive " by default. This is important because we will be using this name in the coding. Step 3. Now, stretch the form length, and include another control named "DirListBox". Note: The control of DirListBox, which you have inserted, is having the property Name set to "Dirl " as shown in the properties colunin. P Step 4. Now, insert one more component each of the same controls (DirListBox) which you have inserted, just adjacent to it, as shown in the figure below:

17 Note: Tlie two new controls DirListBox and DriveListBox which have been inserted in this step Featul-es of are named as "Dirl" and "Drive2" respectively. Visual Basic 6.0 Step 5. Now, insert a new control named "FileListBox" from the ToolBox in the fonn as shown below in tlie figure: Note: The new co~ltrol.included in having its Name property set to "Filel" Now, our aim is to i~iiplementhe copy operation, when we drag a file from "Filel" and drop it in "Dir2". So, to do this, following steps need to be followed: Choose any available source drive from "Drivel" (from which file has to be copied) by simply clicking over it. Choose tlie source directory (from which file has to be copied) from "Dirl" by double clicking on the directory shown in the Directory Box. Repeat the first two steps exactly for "Drive2" and "Dir2" instead of "Drivel" and "Dirl" respectively, for selecting the destination (where the file is to be copied). Select a file from the FileListBox (Filel) by clicking on that file, and drag (moving the mouse with left mouse button pressed) the file to "Dir2" and drop (release the left mouse button) it there. This operation, as given above clearly indicate that we have to write code for the following events: We have to write code for the change event of drivel i.e. in case tlie drive is selected in tlie drive ~ box, changes have to be reflected in the directory box since the directory box is reflecting the directories contained in that drive. Then, we need to override the change event of dirl, since appropriate files need to be reflected in the FileListBox "Filel ".

18 Windows Programming using Visual Basic 6.0 Similarly, we need to write code for the change event of dirve2 i.e., in case the destination drive is selected in the drive box, only those files, which are in the drive need to be shown in the destination Directory Box. Hence, we have to write the code for change event of Drivel, Dirl, and Drive2 as shown below: Private Sub Dirl-Change ( ) File 1.Path = Dir 1 End Sub Private Sub Drive 1-Change ( ) Dirl.Path = Drivel Elid Sub Private Sub Drive2 Change ( ) Dir2.Path = ~rive2- End Sub Now, when we click on a file in the File1 FileListBox, and drag (i.e., an event of mouse move with left button pressed) the file, the Drag Method of the Filel should be called as shown below: Private Sub File1 - MouseMove (Button As nteger, Shift As nteger, X As Single. Y As Single) File l.dragcon = Loadpicture ("C:\Program Files\Microsoft Visual Studio\Vfp98\ - Tools\filer\Filer.ico") f Button = Then File 1.Drag 1 End f End Sub Now, once we start the drag operation from Filel, it has to be dropped at destination directory box i.e. DragDrop Event of Dir2 needs to be called. Here we call the FileCopy method which copies the source file name given as first argument to the destination given as the second argument. And, ultimately, call the source's Drag method to end the drag operation as shown below: Private Sub Dir2-DragDrop (Source As Control, X As Single, Y As Single) Dim st As String st = "\" and Source.FileName FileCopy Source.Path and st, Dir2.Path and st Source.Drag 0 End Sub The Figure shown below depicts the working of the program. As you can see that the source drive, source directory, source file, destination drive and the destination directory has been chosen. t is shown clearly, the change of shape of mouse icon as the mouse is being dragged towards the destination directory box.

19 2.2.3 Linking to Database Let us move on one step further with an important utility of windows programming. Advanced Features of Visual Basic 6.0 Step 1. First, let us take a simulated example of a batch of students studying at GNOU. We allknow, that has to be a file maintained in order to keep track of student details. Now, the structure or we may call the fields to be included in the file may be as follows: Field Data Type Width Rollno Character 5 Name Character 5 0 Age Numeric 2 Sex Character 1 So, before we start with the actual coding, we make a simulation of a database named "dbl" and create a table called "student master" in it through Access 97. So, move to Start button then to programs and then click on Microsoft Access as shown below: Step 2. What we get as the first screen of Microsoft Access is shown below:

20 \Yindows Progrs''ming using Visual Here, on choosing the "Blank Database" option and by clicking on "Ok" button, we get a dialog window as shown below: Step 3. You will get a dialog window as shown above, in which you have to give the name to your new database i.e. "dbl". And then, click on "Create" button. Step 4. We get a blank database created automatically, as shown in the figure below. Now, we have to create a table similar to what has been discussed in step 1 on this application, by clicking on the "New" button..step 5. Here, we get another dialog box in, which choose a method in which we are going to create a new table. So, choose "Design View"; that is the easiest way to create a table amongst all. And then click "Ok" button.

21 Step 6. Now what we get is a window as showing three fields: Field Name, Data Type, and Description. Advanced Features of Visual Basic 6.0 Step 7. n the above given window, fill the information about the table structure discussed in step 1, as shown below: Step 8. n this step you have to choose the rollno field by clicking over it and then make it a "Primary Key", because rollno has to unique and a non Null value. Do this as shown below:

22 Yindows Programming l~sieg Visual Hnsic 6.0 Step 9. Click on the close button as shown below: Step 10. The moment the close button is pressed, you'll get a verification dialog window as show below. Press the "Yes" button. Step 11. On pressing "yes" in the above window, you'll get the following dialogbox, where you need to give the new table a name. Type in "student master" as shown below and press 'LOK": Step 12. On pressing "ok" in the above window you'll get the following window showing the inclusion of the new table wich you have just now created.

23 So, now what you get is a database named "db.mdbm in "C:\My Documents" directory, with a table Advanced Features of named "Student Master" with no records in it. Visual Basic 6.0 Step 13. Now, fill in the records in the table and close the window as shown below in the figure: Step 14. Click the close button of the main application window now, as shown below: Now, the database is ready. Only part left is to provide a front end through Visual Basic and link it with the database. As done in the following steps: r Step 15. Open the new Standard Exe application in VB and you'll get a following screen.

24 Windows Programming using Visual Basic 6.0 Step 16. nsert Labels, TextBoxes (for input and display) and a new control. called "Data Control" as shown in the figure below: Step 17. Change the captions of the components as follows: Label 1 to Rol lno Label2 to Name Label3 to Age Label4 to Sex Delete the caption of all the Text Boxes And change the caption of data control to "student master file" as shown below:

25 i Advanced Features of Step 18. Change the "DatabaseName" property to "C:\My Documents\db.mdb directly, or choose the path where you saved the database, by pressing the ellpses button(...). As Visual Basic 6.0 shown below in the figure.! Step 19. As you have selected the database name in the previous step, its time to select the table which you will be linking your form to. To do this, click on the "RecordSource" property ' of the Data Control, and you'll get all the tables listed, which are a part of the database to which this data control is linked with. P Since only one table was created in the database, only one table is shown in the list. Step 20. Select all the text boxes and change the Datasource property to "Datal", since all the text boxes have to be linked with the database that is linked with data control 'Datal'.

26 \Yindows Programming using Visual nrsic 6.0 Step 2 1. Select the 'textl' textbox and change the DataField property. When yo11 click on the data field property,it will show you a drop downlist as shown in the figure below. All you have to do is to, choose the field with which you want this text box to be linked with. So choose 'rollno' from the list. Step 22. Again, click on the next text box i.e., text2 and change the DataField property of it. So choose 'name' from the list. MS sans Serif weooooooae Step 23. Again, click on the next text box,i.e. text3 and change the DataField property of it. So choose 'age' from the list.

27 i Step 24. Again, click on the next text box,i.e. text4 and change the DataField property of it. So Features of choose 'sex' from the list. Visual Basic 6.0 So, now every control in the form 1 is linked with some or the other component to import the data from the database dbl.mdb which we created in Microsoft Access. Now, save the project and the form at any desired location and run the application as shown in the steps given as follows. Step 25. Now, to start the application click on the start button on the toolbar as shown below:

28 Windows Programming using Visual Raaic 6.n Step 26. The figure below shows how application provides a front end, to navigate the records in the table 'student master' of database 'dbl' created Ms-Access. -+ next last You can click on the navigation buttons to navigate the records in the database. 2.3 SUMMARY This unit establishes a better understanding over some advanced components used in visual programming environment. The form works as a basic interface between the user and the application. t is to be noted that the form acts as a container for all the components that were discussed. Toolbox provides different controls, which can be used on the form for better GU's.