1. Microsoft Visual Basic 2010: Reloaded Fourth Edition Chapter Seven More on the Repetition Structure

2. Objectives After studying this chapter, you should be able to: Code a counter-controlled loop using the For…Next statement Nest repetition structures Calculate a periodic payment using the Financial.Pmt method Select the existing text in a text box Code the TextChanged event procedure for a text box Microsoft Visual Basic 2010: Reloaded, Fourth Edition2

3. Objectives (cont'd.) Code a list box’s SelectedValueChanged and SelectedIndexChanged event procedures Include a combo box in an interface Code the TextChanged event procedure for a combo box Store images in an image list control Display an image stored in an image list control Microsoft Visual Basic 2010: Reloaded, Fourth Edition3

4. The For...Next Statement For...Next statement: processes a set of instructions a known number of times –Is a pretest loop Counter-controlled loop: a loop whose processing is controlled by a counter Counter variable: used to keep track of the number of times the loop has been processed Startvalue, endvalue, and stepvalue items –Control the number of times the loop is processed –Must evaluate to numeric values –Can be positive or negative 4

5. Microsoft Visual Basic 2010: Reloaded, Fourth Edition The For...Next Statement (cont'd.) A negative stepvalue causes the loop counter to count down Decrementing: adding increments of a negative number Flowchart symbol for the For...Next loop is a hexagon Values for the counter variable, startvalue, stepvalue, and endvalue are shown within the hexagon 5

6. Microsoft Visual Basic 2010: Reloaded, Fourth Edition 6 Figure 7-1: How to use the For…Next statement

7. Microsoft Visual Basic 2010: Reloaded, Fourth Edition 7 Figure 7-1: How to use the For…Next statement (cont’d.)

8. Microsoft Visual Basic 2010: Reloaded, Fourth Edition The For...Next Statement (cont'd.) 8 Figure 7-2: Processing steps for Example 1 in Figure 7-1

9. Microsoft Visual Basic 2010: Reloaded, Fourth Edition The For...Next Statement (cont'd.) 9 Figure 7-2: Processing steps for Example 1 in Figure 7-1 (cont’d.)

10. Microsoft Visual Basic 2010: Reloaded, Fourth Edition10 Figure 7-3: Problem specification for the Savings Account application The For...Next Statement (cont'd.)

11. Microsoft Visual Basic 2010: Reloaded, Fourth Edition11 Figure 7-4: Sample run of the Savings Account application The For...Next Statement (cont'd.)

12. Microsoft Visual Basic 2010: Reloaded, Fourth Edition12 Figure 7-5: Pseudocode and flowchart for the Calculate button’s Click event procedure

13. Microsoft Visual Basic 2010: Reloaded, Fourth Edition13 Figure 7-6: Calculate button’s Click event procedure The For...Next Statement (cont'd.)

14. Can use For…Next or Do…Loop for a counter- controlled loop With Do…Loop, you must: –Declare and initialize the counter variable –Update the counter variable –Include an appropriate comparison in the Do clause For…Next statement handles the declaration, initialization, update, and comparison tasks –Is more convenient to use Microsoft Visual Basic 2010: Reloaded, Fourth Edition

15. 15 Figure 7-7: Comparison of the For…Next and Do…Loop statements The For...Next Statement (cont'd.)

16. Nested Repetition Structures Repetition structures can be nested –Can use pretest or posttest loops for outer loop and for inner (nested) loop A clock with minute and second hands demonstrates nested loops –Minute hand moves 1 position, then the second hand moves 60 positions Microsoft Visual Basic 2010: Reloaded, Fourth Edition

17. Figure 7-8: Three versions of the logic used by a clock’s minute and second hands

18. Nested Repetition Structures (cont’d.) Microsoft Visual Basic 2010: Reloaded, Fourth Edition Figure 7-9: Modified problem specification for the Savings Account application Figure 7-9: Sample run of the Savings Account application

19. Nested Repetition Structures (cont’d.) Microsoft Visual Basic 2010: Reloaded, Fourth Edition Figure 7-11: Two versions of the Calculate button’s Click event procedure

20. Microsoft Visual Basic 2010: Reloaded, Fourth Edition Figure 7-11: Two versions of the Calculate button’s Click event procedure (cont’d.)

21. The Payment Calculator Application Microsoft Visual Basic 2010: Reloaded, Fourth Edition Figure 7-12: Problem specification for the Payment Calculator application

22. The Payment Calculator Application (cont’d.) Microsoft Visual Basic 2010: Reloaded, Fourth Edition Figure 7-13: Sample run of the Payment Calculator application

23. Microsoft Visual Basic 2010: Reloaded, Fourth Edition The Financial.Pmt Method Financial.Pmt method –Calculates a periodic payment on a loan or investment –Returns the periodic payment as a Double type value Rate and number of periods arguments must be expressed in the same units (monthly, annual, etc.) 23

24. Microsoft Visual Basic 2010: Reloaded, Fourth Edition24 Figure 7-14: How to use the Financial.Pmt method

25. The Financial.Pmt Method (cont’d.) Microsoft Visual Basic 2010: Reloaded, Fourth Edition Figure 7-15: Pseudocode and code for the Calculate button’s Click event procedure

26. Microsoft Visual Basic 2010: Reloaded, Fourth Edition Figure 7-15: Pseudocode and code for the Calculate button’s Click event procedure

27. Selecting the Existing Text in a Text Box SelectAll method: selects all text in a text box for replacement typing –User only needs to type the new value Enter event: occurs when the text box receives the focus –When the user tabs to the control – When the user uses the control’s access key –When the Focus method sends the focus to the control –When the user clicks in the text box Microsoft Visual Basic 2010: Reloaded, Fourth Edition27

28. Selecting the Existing Text in a Text Box (cont'd.) Microsoft Visual Basic 2010: Reloaded, Fourth Edition28 Figure 7-16: How to use the SelectAll method

29. Microsoft Visual Basic 2010: Reloaded, Fourth Edition29 Figure 7-17: Loan text box’s Enter event procedure Selecting the Existing Text in a Text Box (cont'd.)

30. Microsoft Visual Basic 2010: Reloaded, Fourth Edition30 Figure 7-18: Result of processing the text box’s Enter event procedure Selecting the Existing Text in a Text Box (cont'd.)

31. Entering a new value in the Loan text box does not update the monthly payments until the user clicks the Calculate button –May cause confusion Microsoft Visual Basic 2010: Reloaded, Fourth Edition31 Figure 7-19: New loan amount entered in the Loan text box

32. Coding the TextChanged Event Procedure TextChanged event –Occurs when a change is made in a control’s Text property –Change may be made by user or the program Microsoft Visual Basic 2010: Reloaded, Fourth Edition32 Figure 7-20: New principal entered in the Principal text box

33. Microsoft Visual Basic 2010: Reloaded, Fourth Edition33 Figure 7-21: Result of processing the text box’s TextChanged event procedure Coding the TextChanged Event Procedure (cont’d.)

34. Coding the SelectedValueChanged and SelectedIndexChanged Event Procedures Microsoft Visual Basic 2010: Reloaded, Fourth Edition34 Figure 7-22: The list box’s SelectedValueChanged and SelectedIndexChanged event procedures

35. Including a Combo Box in an Interface Combo Box control: –Similar to a list box with a list of choices –List portion may be hidden –May contain a text field that allows the user to type an entry that is not on the list Three styles of combo boxes, controlled by the DropDownStyle property: –Simple –DropDown (the default) –DropDownList Microsoft Visual Basic 2010: Reloaded, Fourth Edition35

36. Using a Combo Box in an Interface Microsoft Visual Basic 2010: Reloaded, Fourth Edition36 Figure 7-23: Examples of the three styles of combo boxes

37. Microsoft Visual Basic 2010: Reloaded, Fourth Edition37 Figure 7-24: Code used to fill the combo boxes in Figure 7-23 with values

38. Using a Combo Box in an Interface (cont'd.) Items.Add method: used to add items to a combo box SelectedItem property: contains the value of the selected item in the list Text property: contains the value that appears in the text portion of the control (item selected or typed in) Items.count property: used to obtain the number of items in the combo box Sorted property: used to sort the items in the list 38Microsoft Visual Basic 2010: Reloaded, Fourth Edition

39. Using a Combo Box in an Interface (cont'd.) 39 Figure 7-25: Sample run of the Payment Calculator application using a combo box Microsoft Visual Basic 2010: Reloaded, Fourth Edition

40. 40 Figure 7-26: Code for the Payment Calculator application shown in Figure 7-25 Microsoft Visual Basic 2010: Reloaded, Fourth Edition

41. 41 Figure 7-26: Code for the Payment Calculator application shown in Figure 7-25 (cont’d.) Microsoft Visual Basic 2010: Reloaded, Fourth Edition

42. Using an Image List Control Image List control: –Stores a collection of images –Does not appear on the form; appears in the component tray Add images to the control using the Images Collection Editor window Microsoft Visual Basic 2010: Reloaded, Fourth Edition

43. Using an Image List Control (cont’d.) Figure 7-27: Image Viewer application Microsoft Visual Basic 2010: Reloaded, Fourth Edition

44. Using an Image List Control (cont’d.) Figure 7-28: How to add images to an image list control’s Images collection Microsoft Visual Basic 2010: Reloaded, Fourth Edition

45. Using an Image List Control (cont’d.) Figure 7-29: Completed Images Collection Editor window in the Image Viewer application Microsoft Visual Basic 2010: Reloaded, Fourth Edition

46. Using an Image List Control (cont’d.) Figure 7-30: How to refer to an image in the Images collection Microsoft Visual Basic 2010: Reloaded, Fourth Edition

47. Using an Image List Control (cont’d.) Figure 7-31: Sample run of the Image Viewer application Microsoft Visual Basic 2010: Reloaded, Fourth Edition

48. Using an Image List Control (cont’d.) Figure 7-32: Code entered in the View button’s Click event procedure Microsoft Visual Basic 2010: Reloaded, Fourth Edition

49. Creating the Slot Machine Application Programming Tutorial 1 49 Figure 7-34: MainForm in the Slot Machine application Microsoft Visual Basic 2010: Reloaded, Fourth Edition

50. Creating the Birmingham Sales Application Programming Tutorial 2 50 Figure 7-40: MainForm for the Birmingham Sales application Microsoft Visual Basic 2010: Reloaded, Fourth Edition

51. Programming Example 51 Raise Calculator Application Figure 7-46: MainForm for the Raise Calculator application Microsoft Visual Basic 2010: Reloaded, Fourth Edition

52. Summary For...Next statement: a pretest loop that will process the instructions a fixed number of times A variable declared in a For clause has block scope Use a hexagon in a flowchart for a For…Next loop Financial.Pmt method: calculates a periodic payment on a loan or investment SelectAll method: highlights text in a text box TextChanged event: occurs when a control’s text changes 52Microsoft Visual Basic 2010: Reloaded, Fourth Edition

53. Summary (cont'd.) Combo box: similar to a list box but may not expose the list items until clicked Three styles of combo boxes: Simple, DropDown, and DropDownList Combo box’s Items.Add method: adds an item to the list Use SelectedItem, SelectedIndex, or Text property of a combo box to set the default item in a combo Combo box’s Items.Count property: used to obtain the number of items listed in the combo box 53Microsoft Visual Basic 2010: Reloaded, Fourth Edition

54. Summary (cont'd.) Combo box’s Sorted property: used to sort items listed in a combo box Combo box’s SelectedItem property: contains the value of the item selected in the list portion of the combo box Combo box’s Text property: contains the value that appears in the text portion of the combo box Combo box’s TextChanged event: occurs when the user either selects an item in the list portion or types a value in the text portion 54Microsoft Visual Basic 2010: Reloaded, Fourth Edition

55. Summary (cont'd.) Image list control: stores a set of images in its Images collection Images in an image list control belong to the Images collection Access an image in the Images collection using the Item property with the index of the desired image Image collection’s Count property contains the number of images in the collection Use a picture box control to display an image contained in an image list control 55Microsoft Visual Basic 2010: Reloaded, Fourth Edition