Computer Programming Concepts and Visual Basic David I. Schneider

290 Computer Programming Concepts and Visual Basic
hidden contents of lstBox.ItemData( ) can be used by the programmer to index records. As illustrated
in Example 2, they can also be used to set up parallel arrays that hold other data associated
with each item displayed in the list box.
EXAMPLE 2
The following program uses NewIndex and ItemData to provide data about inventions. When an item is
highlighted, its ItemData value is used to locate the appropriate entries in the inventor( ) and date( ) arrays.
Assume the file INVENTOR.TXT contains the following three lines:
“Ball-point pen”, “Lazlo and George Biro”, 1938
“Frozen food”, “Robert Birdseye”, 1929
“Bifocal lenses”, “Ben Franklin”, 1784
‘In the (Declarations) section of (General)
Dim inventor(0 To 10) As String
Dim yr(0 To 10) As Integer
Object Property Setting
frmInvent Caption Inventions
lstInvents Sorted True
lblInventor Caption Inventor
lblWho Caption (none)
lblYear Caption Year
lblWhen Caption (none)
Private Sub Form_Load()
Dim what As String, who As String, when As Integer, index As Integer
Open “INVENTOR.TXT” For Input As #1
index = 0
Do While (index [[ UBound(inventor)) And (Not EOF(1))
Input #1, what, who, when
index = index + 1
lstInvents.AddItem what
lstInvents.ItemData(lstInvents.NewIndex) = index
inventor(index) = who
yr(index) = when
Loop
Close #1
End Sub
Private Sub lstInvents_Click()
lblWho.Caption = inventor(lstInvents.ItemData(lstInvents.ListIndex))
lblWhen.Caption = Str(yr(lstInvents.ItemData(lstInvents.ListIndex)))
End Sub
[Run, and then highlight the second entry in the list.]
THE COMBO BOX CONTROL
A combo box is best thought of as a text box with a help list attached. With an ordinary text
box, the user must type information into the box. With a combo box, the user has the option of