Irwin/McGraw-Hill Copyright© 2000 by the McGraw-Hill Companies, Inc. PowerPoint® Presentation to accompany prepared by James T. Perry University of San Diego

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill Ch 7: Lists, Loops, & Printing  List Boxes & Combo Boxes  Populating list boxes and combo boxes  Do Loops, For/Next Loops  MsgBox returned values  String Functions  Send Info. to the Printer with Print method  Formatting Output

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill List Boxes & Combo Boxes  List/Combo boxes allow a list of items  Types include –simple combo boxes –dropdown combo boxes –dropdown lists  Combo box has style property; list does not  Combo box has design-time text property; list box has only run-time text property.  Combo box does not have a MaxLength property; a list box does.

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill Filling the List  You can fill the list at design- or run-time  Fill at design time if list rarely changes –Click List property, type entry, press Ctrl+Enter –Make Sorted property true to keep list in order  Fill at run time if list is volatile –Use AddItem method to add items –Form: object.AddItem value [,Index] –Example: lstFruits.AddItem "Apple"

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill List/Combo Box Methods  AddItem - Add item to list cboFruits.AddItem "Kiwi" cboFruits.AddItem cboFruits.Text  Clear - Delete all items from the list cboFruits.Clear

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill List/Combo Box Properties  Sorted maintains list in order (if true)  ListIndex holds user-selected item index number (begins at zero, -1 if none selected)  ListCount is number of items in list  List object.List(index) extracts string value of list item  Setting the ListIndex property highlights a selection in the list

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill List/Combo box Events  Change Occurs when user types text into combo box (list box does not have this)  GotFocus Occurs when control receives control  LostFocus Occurs when control loses control

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill Do Loops (1)  Allow repeated execution of instructions  Do loop terminates on a condition you specify  Do loop can test for condition at –Top of loop (pretest) –Bottom of loop (posttest)

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill Do Loops (2)  Loops can continue while a condition is either true or false –Go while True:…While condition –Go while False:…Until condition  Be sure to change the loop variable within the loop or it will loop infinitely!

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill For/Next Loops (1)  For/Next allows you to repeat series of instructions using a counter (a loop index)  Form: For loopindex = initialvalue To endvalue [Step k] …body of loop… Next [loopindex]

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill For/Next Loops (2)  You can loop “backwards” by using a negative increment  Loop testing is done before executing body  Do not change the loop control inside the body  Halt infinite loops by pressing Ctrl+Break  Exit For allows early For loop exit from within the body

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill For/Next Loops (3)  Use For/Next loop when you know the number of times a loop will run  When loop decrements, the test is for strictly less than the ending value  The For/Next ending condition may exist before entering the loop. If so, then the loop body is skipped

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill Using the MsgBox Function  MsgBox has a function form (we have used statement form until now)  MsgBox function returns which key the user pressed of those available  Use VB intrinsic constants to determine which key was pressed.

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill MsgBox Values ConstantValueButton Pressed vbOK 1OK vbCancel 2Cancel vbAbort 3Abort vbRetry 4Retry vbIgnore 5Ignore vbYes 6Yes vbNo 7No (ignore the Value column; use intrinsic constants)

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill Using String Functions  Left(str, nchars) - extract left nchars  Right(str, nchars) - extract right nchars  Mid(str,start,[nchars]) - get middle chars  str is any string, nchars is integer, and start is integer number of starting position.  Len(str) returns # chars in string

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill Using String Functions (2)  String functions and looping facilitate the “zooming” feature of many Microsoft list boxes and combo boxes.  “Zooming” causes a search of the list, refining the search with each additional keystroke the user enters.

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill Sending Info. to the Printer  Visual Basic’s Print method applies to a Form, a printer object, the Debug window, or a picture box  Printer.Print — sends output to printer  Print is a method of the Printer object  Printing is somewhat difficult, because VB is designed to use with forms, not printers

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill Formatting Lines  Printer.print x, y, z prints in three "zones"  Printer.print x;y;z ignores zones  Trailing comma or semicolon causes next print method to continue the line  Each.print starts on a new line  Printer.print (alone) prints blank line

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill Formatting Lines  Tab(20) advances to 20th position: Printer.Print Tab(20); "Name:"  Spc(17) inserts spaces (17) in line  Numbers print with one space for sign of #  Printer.NewPage sends page to printer & goes to new page  Printer.EndDoc sends page to printer & halts print job

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill Printing to Picture Box  You can use Print method with a picture box to avoid actually printing a result:  picMyPictureBox.Print "howdy" prints to a picture box

Copyright© 2000 by the McGraw-Hill Companies, Inc.Irwin/McGraw-Hill Hands-On Programming Example