Unit-4: Visual programming lecture notes (Controls ) P.R.Engineering college

Unit-4: Visual programming lecture notes (Controls ) in Visual programming uploaded at P.R.Engineering college

Unit-4: Visual programming lecture notes (Controls ) in Visual programming at P.R.Engineering college P.R.Engineering college Staff uploaded in lecturenotes.net

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INTRODUCTION
 
This unit explores the most common types of dialog window applications: the modal dialog and modeless dialog based applications. It also provides an overview of the various controls and their usage in windows applications.

Almost every Windows-based program uses a dialog window to interact with the user. The dialog might be a simple OK message box, or it might be a complex data entry form. A dialog is truly a window that receives messages, that can be moved and closed, and that can even accept drawing instructions in its client area.

LEARNING OBJECTIVES

1. Understand the fundamentals of Dialog based applications and program dialog windows
2. Know the various controls and their usage in dialog based applications
3. Learn to program Modeless dialogs and the fundamentals of windows common dialogs.

DIALOG BASED APPLICATIONS

Applications for Windows frequently communicate with the user through dialog boxes. Class CDialog provides an interface for managing dialog boxes, the Visual C++ dialog editor makes it easy to design dialog boxes and create their dialog-template resources, and Code wizards simplify the process of initializing and validating the controls in a dialog box and of gathering the values entered by the user.

Dialog boxes contain controls, including:

• Windows common controls such as edit boxes, pushbuttons, list boxes, combo boxes, tree controls, list controls, and progress indicators.
• ActiveX controls.
• Owner-drawn controls: controls that you are responsible for drawing in the dialog box.
 
There are two kinds of dialogs: Modal and Modeless. Most dialog boxes are modal, which require the user to close the dialog box before using any other part of the program. But it is possible to create modeless dialog boxes, which let users work with other windows while the dialog box is open. MFC supports both kinds of dialog box with class CDialog. The controls are arranged and managed using a dialog-template resource, created with the dialog editor.

Property sheets, also known as tab dialog boxes, are dialog boxes that contain “pages” of distinct dialog-box controls. Each page has a file folder “tab” at the top. Clicking a tab brings that page to the front of the dialog box.

You can use class CDialog to manage two kinds of dialog boxes:

• Modal dialog boxes, which require the user to respond before continuing the program
• Modeless dialog boxes, which stay on the screen and are available for use at any time but permit other user activities

The resource editing and procedures for creating a dialog template are the same for modal and modeless dialog boxes.

Steps in creating a dialog box

Creating a dialog box for your program requires the following steps:

1. Use the dialog editor to design the dialog box and create its dialog-template resource.
2. Create a dialog class.
3. Connect the dialog resource’s controls to message handlers in the dialog class.
4. Add data members associated with the dialog box’s controls and to specify dialog data exchange and dialog data validations for the controls.

During the life cycle of a dialog box, the user invokes the dialog box, typically inside a command handler that creates and initializes the dialog object, the user interacts with the dialog box, and the dialog box closes.

For modal dialog boxes, your handler gathers any data the user entered once the dialog box closes. Since the dialog object exists after its dialog window has closed, you can simply use the member variables of your dialog class to extract the data.

For modeless dialog boxes, you may often extract data from the dialog object while the dialog box is still visible. At some point, the dialog object is destroyed; when this happens depends on your code.
 
Modal dialog

With a modal dialog, such as the Open File dialog, the user cannot work elsewhere in the same application (more correctly, in the same user interface thread) until the dialog is closed. Lets examine the program 4.1 and understand the steps involved in creating a modal dialog.

Program 4.1: Program to create a new Dialog based Project

1. To create a new project, start by clicking on File in the menu of the Visual C++ 6 window then on New.
2. Write Dialog1 in the project name and choose an MFC AppWizard (exe) from the list of the available Wizards, then click OK. The MFCApplication Wizard will start.
3. In Step 1 of the Wizard, click on Dialog based option, then click Next.
4. In Steps 2 and 3 accept the default settings, just click Next to do this.
5. In Step 4 click Finish, then you will get the project information. Click OK.
6. Designing the Dialog: Click on the text TODO : Place dialog controls here, then press Delete. This will remove the unwanted text label
 
Figure 4.1 An empty dialog window during design phase

7. Click on bottom right edge of the dialog box. A rectangle appears around the edges of the box itself. Resize the dialog box using the sizing points as shown below.
8. Click on the sizing point on the bottom-right corner, keeping the mouse button pressed. Move the mouse, keeping the button pressed. An outline of the new dialog box size is shown as the mouse is moved. Release the mouse button when the dialog box size is 230 x 126.
9. Click on the Cancel button and press Delete to remove the Cancel button, then right click the mouse on the OK button and a context menu will appear as shown in figure 4.2.
10. Select Properties from the context menu.
11. The Push Button Properties dialog box appears. Select the General tab; then in Caption box replace the word OK with Close as shown in figure

Figure 4.2 Context menu
 
Figure 4.3 Push button properties

12. On the controls toolbar, select the static text control. Click the dialog box near the upper left corner. A static text control appears on the dialog box, with the default text Static.
 
13. Static text controls can be used to display some information (we going to use few of them as labels). You need three static text controls. Therefore, you need to repeat the process of dropping static text control on to the dialog box make sure to drop each control next to each other.
14. On the controls toolbar, select the edit control and as you did before with text control. Drop two edit controls. Select Combo Box from the controls toolbar and drop it into the dialog box. Then select List Box control and drop it to the dialog box. Select button control from the controls toolbar and drop it into the dialog box.
15. Change the Caption of the new button to Add and its ID to IDC_ADD, then arrange the controls on the dialog box as show below. Right click static text control and change its properties change Caption to Title as shown in figure 4.4.
 
Figure 4.4 Text Properties

16. Change the Caption for each static text control as shown in figure 4.5. Change the  ID in Edit Properties for first Edit Box control to IDC_FIRSTNAME and the second edit control to IDC_LASTNAME.
 
Figure 4.5 Changing the Caption for each static text control
 
17. Change the ID in List Box Properties to IDC_NAMELIST and the ID Combo Box Properties to IDC_TITLE.
18. Click on Data in Combo Box Properties and populate the Data as shown in figure 4.6. After each entry is added in the list remember to press Ctrl + Enter to go to a new line.
 
Figure 4.6 Combo Box Properties

19. On the Styles tab, change the Combo Box’s Type to Drop List. Position your mouse over the Combo Box dropdown button then left-click. Another rectangle will appear (see figure 4.7) that allows you to specify the size of the open Combo Box’s List.
 
Figure 4.7 Dialog box in between the design

20.  Assigning Member variables to Controls: Press Ctrl + W to start ClassWizard, or from the View menu select ClassWizard. The MFC ClassWizard dialog box appears as shown below. Select the Member Variables tab, then select the dialog class in the Class name : combo box; use CDialog1Dlg. Select

Title:
Unit-4: Visual programming lecture notes (Controls )

Subject:
Visual programming

Institute:
P.R.Engineering college

Unit-4: Visual programming lecture notes (Controls ) P.R.Engineering college

Unit-4: Visual programming lecture notes (Controls ) in Visual programming uploaded at P.R.Engineering college

Summary / document preview text:

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