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Microsoft Visual Basic 2010: Reloaded Fourth Edition

Microsoft Visual Basic 2010: Reloaded Fourth Edition. Chapter Seven More on the Repetition Structure. Objectives. After studying this chapter, you should be able to: Code a counter-controlled loop using the For…Next statement Nest repetition structures

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Microsoft Visual Basic 2010: Reloaded Fourth Edition

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  1. Microsoft Visual Basic 2010: ReloadedFourth 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 Edition 2

  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 Edition 3

  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 Microsoft Visual Basic 2010: Reloaded, Fourth Edition 4

  5. 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 Microsoft Visual Basic 2010: Reloaded, Fourth Edition 5

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

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

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

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

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

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

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

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

  14. The For...Next Statement (cont'd.) • 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. The For...Next Statement (cont'd.) Figure 7-7: Comparison of the For…Next and Do…Loop statements Microsoft Visual Basic 2010: Reloaded, Fourth Edition 15

  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 Microsoft Visual Basic 2010: Reloaded, Fourth Edition

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

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

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

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

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

  23. 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.) Microsoft Visual Basic 2010: Reloaded, Fourth Edition 23

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

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

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

  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 Edition 27

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

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

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

  31. Selecting the Existing Text in a Text Box (cont'd.) • 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 Figure 7-19: New loan amount entered in the Loan text box Microsoft Visual Basic 2010: Reloaded, Fourth Edition 31

  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 Figure 7-20: New principal entered in the Principal text box Microsoft Visual Basic 2010: Reloaded, Fourth Edition 32

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

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

  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 Edition 35

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

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

  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 Microsoft Visual Basic 2010: Reloaded, Fourth Edition 38

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

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

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

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

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

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