Option-Based Controls

This application is used to illustrate different ways of using or implement the check box controls, including its properties, methods, and events.

Practical Learning: Introducing Check Boxes

1. Start a new project with its default form
2. Save it in a new folder named FastFood1
3. Save the unit as Exercise and save the project as FastFood
4. Open Image Editor. Design a 32 x 32 and 16 x 16 icon as follows:
    
   
5. Save it as FastFood in the folder of the current project
6. Create a new 16 x 16 size bitmap and design it as follows:
    
   
7. Save it as Ingredients in the folder of the current project
8. In the project options (Project -> Options), access the Application tab. Set the Title to Fast Food Corner and sect the icon to the above FastFood icon
9. Change the form’s following properties:
   BorderStyle: bsDialog
   Caption: Fast Food Restaurant – Customer Menu
   Name: frmMain
   Position: poScreenCenter
10. Design the dialog box as follows:
     

    Control Name Caption Other Properties GroupBox   Bread   RadioButton rdoBun B&un Alignment: taLeftJustify RadioButton rdoRoll &Roll Alignment: taLeftJustify Checked: true Group Box   Meat   Radio Button rdoBeefPatty Bee&f Patty Alignment: taLeftJustify Checked: true Radio Button rdoGrilledChicken &Grilled Chicken Alignment: taLeftJustify Radio Button rdoChickedBreast C&hicken Breast Alignment: taLeftJustify GroupBox   Ingredients

11. Save All
12. On the Standard toolbar, click the New button . In the New Items dialog box, click Dialogs and double-click Standard Dialog (Vertical)
13. Save it as Ingredients
14. Change its Name to dlgIngredients
15. Change its Caption to Ingredients Selection
16. Design the dialog box as follows:
     

    Control Name Caption Other Properties CheckBox chkLettuce &Lettuce Alignment: taLeftJustify Checked: true CheckBox chkOnion &Onion Alignment: taLeftJustify CheckBox chkTomato &Tomato Alignment: taLeftJustify Checked: true CheckBox chkPickles &Pickles Alignment: taLeftJustify

17. Display the main form (View -> Forms… -> frmMain -> OK)
18. Complete its design as follows:
     

    Control Name Caption Other Properties CheckBox chkRegulars &Regulars Alignment: taLeftJustify AllowGrayed: true CheckBox chkSweetener &Sweetener Alignment: taLeftJustify Checked: true CheckBox chkCheese Ch&eese Alignment: taLeftJustify CheckBox chkBacon B&acon Alignment: taLeftJustify GroupBox   Options   BitBtn btnIngredients &Ingredients Glyph: Ingredients RadioButton rdoMayonnaise &Mayonnaise Alignment: taLeftJustify Checked: true RadioButton rdoKetchup &Ketchup Alignment: taLeftJustify RadioButton chkMustard Mus&tard Alignment: taLeftJustify Bevel     Shape: bsFrame BitBtn     Kind: bkClose Label   Total Price:   Edit edtTotalPrice $2.35

19. On the main form, double-click the Ingredients button and implement its OnClick() event as follows:
     

    //--------------------------------------------------------------------------- #include <vcl.h> #pragma hdrstop #include "Exercise.h" #include "Ingredients.h" //--------------------------------------------------------------------------- #pragma package(smart_init) #pragma resource "*.dfm" TfrmMain *frmMain; //--------------------------------------------------------------------------- __fastcall TfrmMain::TfrmMain(TComponent* Owner) : TForm(Owner) { } //--------------------------------------------------------------------------- void __fastcall TfrmMain::btnIngredientsClick(TObject *Sender) { dlgIngredients->ShowModal(); } //---------------------------------------------------------------------------

20. Test the application. Close it and return to Bcb
21. Save All
22. If the user completely removes the check mark on the Sweetener check box, this suggests that the customer does not want this item on the sandwich. Consequently, the radio buttons in the Options group should be disabled. When the user clicks a check box, whether the control was already checked or not, the OnClick() event fires. Therefore, in this case, the first thing you should do it to check the state of the check button and then implement a behavior accordingly.
    Display the main form and double-click the Sweetener check control
23. Implement its OnClick event as follows:
     

    //--------------------------------------------------------------------------- void __fastcall TfrmMain::chkSweetenerClick(TObject *Sender) { // If the sweetener check box is not checked if( chkSweetener->Checked == False ) { // Disable the Options radio buttons rdoMayonnaise->Enabled = False; rdoKetchup->Enabled = False; rdoMustard->Enabled = False; } else { // Otherwise, enable the Options radio buttons rdoMayonnaise->Enabled = True; rdoKetchup->Enabled = True; rdoMustard->Enabled = True; } } //---------------------------------------------------------------------------

24. To keep track of the user’s selection of ingredients, we will use four global variables that each represents a check box from the Ingredients dialog.
    In the header file of the main form, declare four private Boolean variables as follows:
     

    private: Boolean bLettuce, bOnion, bTomato, bPickles;

25. In the constructor of the main form, initialize the variables with a false value each:
     

    //--------------------------------------------------------------------------- __fastcall TfrmMain::TfrmMain(TComponent* Owner) : TForm(Owner) { bLettuce = False; bOnion = False; bTomato = False; bPickles = False; } //---------------------------------------------------------------------------

26. When the user clicks the Regulars check box, we will update the global variables appropriately.
    On the form, double-click the Regulars check box and implement its OnClick() event as follows:
     

    //--------------------------------------------------------------------------- void __fastcall TfrmMain::chkRegularsClick(TObject *Sender) { // If the Regulars check box is completely unchecked if( chkRegulars->State == cbUnchecked ) { // Set the global Boolean variables to false each bLettuce = False; bOnion = False; bTomato = False; bPickles = False; } // If the Regulars check box is completely checked else if( chkRegulars->State == cbChecked ) { // Set the global Boolean variables to true each bLettuce = True; bOnion = True; bTomato = True; bPickles = True; } // Otherwise, refer to the state of the check boxes // from the Ingredients dialog box. Whatever they are else { bLettuce = dlgIngredients->chkLettuce->Checked; bOnion = dlgIngredients->chkOnion->Checked; bTomato = dlgIngredients->chkTomato->Checked; bPickles = dlgIngredients->chkPickles->Checked; } } //---------------------------------------------------------------------------

27. When the Regulars check box is not checked at all, no basic ingredient is selected. When this control is checked, all ingredients will be added to the sandwich. If at least one ingredient is selected and at least one ingredient is not selected, the Regulars check box should appear grayed.
    When the user clicks the Ingredients button, we will display the Ingredients Selection dialog box and allow the user to select the ingredients. If the user clicks OK to dismiss the dialog box, we will apply the above scenario.
    On the form, double-click the Ingredients button and change its OnClick event as follows:
     

    //--------------------------------------------------------------------------- void __fastcall TfrmMain::btnIngredientsClick(TObject *Sender) { // Before displaying the dialog box, synchronize its // check boxes with the global variables dlgIngredients->chkLettuce->Checked = bLettuce; dlgIngredients->chkOnion->Checked = bOnion; dlgIngredients->chkTomato->Checked = bTomato; dlgIngredients->chkPickles->Checked = bPickles; // Call the Ingregients Selection dialog box for the user // If the user clicked OK when closing the dialog box, dlgIngredients->ShowModal(); if( dlgIngredients->ModalResult == mrOk ) { // If the user clicks OK, update the global values of the check boxes bLettuce = dlgIngredients->chkLettuce->Checked; bOnion = dlgIngredients->chkOnion->Checked; bTomato = dlgIngredients->chkTomato->Checked; bPickles = dlgIngredients->chkPickles->Checked; // if no check box is checked if( (bLettuce == False) && (bOnion == False) && (bTomato == False) && (bPickles == False) ) chkRegulars->State = cbUnchecked; // then uncheck this one // if all check boxes are checked else if( (bLettuce == True) && (bOnion == True) && (bTomato == True) && (bPickles == True) ) chkRegulars->State = cbChecked; // then check this one else // if at least one check box is checked and at one is unchecked chkRegulars->State = cbGrayed; // then set this one as indeterminate } // If the user clicked Cancel, don't do nothing } //---------------------------------------------------------------------------

28. Now we can calculate the price of the sandwich.
    In the header file of the main form, declare a private member function of type void __fastcall named EvaluatePrice
    
    
29. Implement the method as follows:
     

    //--------------------------------------------------------------------------- void __fastcall TfrmMain::EvaluatePrice() { //TODO: Add your source code here double PriceBread, PriceMeat, PriceCheese, PriceBacon, TotalPrice; // The price of bread is $0.85 PriceBread = 0.85; // To get the price of the meat, find out what button // is selected in the Meat group box if( rdoBeefPatty->Checked == True ) // The beef patty is $1.50 PriceMeat = 1.50; else if( rdoGrilledChicken->Checked == True || rdoChickenBreast->Checked == True ) // Cheicken breast and grilled chicken are $1.80 each PriceMeat = 1.80; else // Just in case PriceMeat = 0.00; // There is no extra cost for the Regular ingredients // and nothing to add for the sweetener // On the other hand, // if the customer wants cheese, $0.30 is added to the price if( chkCheese->Checked == True ) PriceCheese = 0.30; else // otherwise, the customer don't want no cheese PriceCheese = 0.00; // If the customer wants bacon, $0.45 is added to the price if( chkBacon->Checked == True ) PriceBacon = 0.45; else PriceBacon = 0.00; // Now, we can calculte the total price TotalPrice = PriceBread + PriceMeat + PriceCheese + PriceBacon; edtTotalPrice->Text = FloatToStrF(TotalPrice, ffCurrency, 8, 2); } //---------------------------------------------------------------------------

30. To update the price and its display live whenever the user makes a new selection, double-click the following controls: Beef Patty, Grilled Chicken, Chicken Breast, Cheese, and Bacon
31. In the body of each, simply call the above EvaluatePrice() method:
     

    //--------------------------------------------------------------------------- void __fastcall TfrmMain::rdoBeefPattyClick(TObject *Sender) { EvaluatePrice(); } //--------------------------------------------------------------------------- void __fastcall TfrmMain::rdoGrilledChickenClick(TObject *Sender) { EvaluatePrice();  } //--------------------------------------------------------------------------- void __fastcall TfrmMain::rdoChickedBreastClick(TObject *Sender) { EvaluatePrice(); } //--------------------------------------------------------------------------- void __fastcall TfrmMain::chkCheeseClick(TObject *Sender) { EvaluatePrice(); } //--------------------------------------------------------------------------- void __fastcall TfrmMain::chkBaconClick(TObject *Sender) { EvaluatePrice(); } //---------------------------------------------------------------------------

32. Test the application:
     
    
33. Close it and return to Bcb
34. Heighten the form and add the following controls to the top section
    
     
    
     

    Control	Name	Caption/Text	Other Properties
    Label		Processed By:
    Edit	edtClerk
    Label		Order Date:
    MaskEdit	edtOrderDate		EditMask: !99/99/0000;1;_

35. Save All