Table 7-6. Property settings for the controls on the directory list form
Control | Property | Setting |
Text box | Name | txtFileSpec |
| AfterUpdate | [Event Procedure] |
List box | Name | lstDirList |
| RowSourceType | FillList |
| AfterUpdate | [Event Procedure] |
- Enter the following code in the text boxs AfterUpdate event procedure. (See the Preface for more information on creating event procedures.) This code forces the list box to requery itself when you enter a value in the text box, and then move to some other control:
Sub txtFileSpec_AfterUpdate ( )
Me.lstDirList.Requery
End Sub
- Enter the following code in the list box's AfterUpdate event. This is sample code that pops up a message box indicating which file you chose:
Sub lstDirList_AfterUpdate ( )
MsgBox "You chose: " & Me.lstDirList.Value
End Sub
- Enter the following code into a global module so that it can be called from any form. Though this code would work fine in a form's module, it's general enough that it will serve you best as part of a global module that can be copied from one database to another. This is the function that fills the array of files:
Public Function FillDirList(ByVal strFileSpec As String, _
astrFiles() As String) As Integer
' Given the file specification in strFileSpec, fill in the
' dynamic array passed in avarFiles().
Dim intNumFiles As Integer
Dim strTemp As String
On Error GoTo HandleErr
intNumFiles = 0
' Set the filespec for the dir() and get the first filename.
strTemp = Dir(strFileSpec)
Do While Len(strTemp) > 0
intNumFiles = intNumFiles +
1
astrFiles(intNumFiles - 1) = strTemp
strTemp = Dir
Loop
ExitHere:
If intNumFiles > 0 Then
ReDim Preserve astrFiles(intNumFiles - 1)
acbSortArray astrFiles()
End If
FillDirList = intNumFiles
Exit Function
HandleErr:
Select Case Err.Number
Case 9
' The array needs to be resized
' Just add room for 100 more files.
ReDim Preserve astrFiles(intNumFiles + 100)
Resume
Case Else
FillDirList = intNumFiles
Resume ExitHere
End Select
End Function
Rather than resizing the array for each matching file name, the Fill-DirList function traps the error that occurs when the array is full, and resizes it 100 slots at a time. Using the Redim Preserve statement is quite expensive in VBA, and you should consider looking for ways to call it as seldom as possible. In this example, the code resizes the array to the correct size once it's done filling in all the file names.
- Import basSortArray from 07-08.MDB. This is the same sorting code that we used in the Solution in Recipe 7.7.
Discussion
The list box in this example uses a list-filling callback function, FillList, to supply its data. (See the Solution in Recipe 7.5 for information on callback functions.) Here's the code:
Private Function FillList(ctl As Control, _
varID As Variant, lngRow As Long, lngCol As Long, _
intCode As Integer)
Static astrFiles() As String
Static intFileCount As Integer
Select Case intCode
Case acLBInitialize
If Not IsNull(Me.txtFileSpec) Then
intFileCount = FillDirList(Me.txtFileSpec, astrFiles())
End If
FillList = True
Case acLBOpen
FillList = Timer
Case acLBGetRowCount
FillList = intFileCount
Case acLBGetValue
FillList = astrFiles(lngRow)
Case acLBEnd
Erase astrFiles
End Select
End Function
In FillList's acLBInitialize case, it calls the FillDirList function to fill in the astrFiles array, based on the value in the txtFileSpec text box. FillDirList fills in the array, calling acbSortArray along the way to sort the list of files, and returns the number of files it found. Given that completed array, FillList can return the value from the array that it needs when requested in the acLBGetValue case. It uses the return value from
FillDirList, the number of files found, in response to the acLBGetRowCount case.
There's also an interesting situation you should note in the FillList and FillDirList routines. FillList declares a dynamic array, astrFiles, but doesn't give a size because it doesn't yet know the number of files that will be found. FillList passes the array off to FillDirList, which adds filenames to the array based on the file specification until it doesn't find any more matches. FillDirList returns the number of matching filenames, but it also has the side effect of having set the array's size and filled it in. Here's the code that does the work. This code fragment uses the ReDim Preserve keywords to resize the array every time it finds a matching filename:
' Set the filespec for the dir() and get the first filename.
strTemp = Dir(strFileSpec)
Do While Len(strTemp) > 0
intNumFiles = intNumFiles + 1
astrFiles(intNumFiles - 1) = strTemp
strTemp = Dir
Loop
FillDirList uses the Dir function to create the list of files. This function is unusual in that you call it multiple times. The first time you call it, you send it the file
specification you're trying to match, and Dir returns the first matching filename. If it returns a nonempty value, you continue to call it, with no parameters, until it does return an empty value. Each time you call Dir, it returns the next matching filename.
Once FillDirList has finished retrieving the list of filenames, it sorts the names in the array. Its return value is the number of files it found. The following code shows how this works:
If intNumFiles > 0 Then
ReDim Preserve astrFiles(intNumFiles - 1)
acbSortArray astrFiles()
End If
FillDirList = intNumFiles
Note that when Access calls the list-filling callback function, values for the lngRow and lngCol parameters are always zero-based. Therefore, when you use arrays within callback functions, you should always consider using zero-based arrays to hold the data you'll display in the control. If you don't, you'll always be dealing with "off by one" errors. Using a zero-based array will mean that the row values (sent to your code in lngRow) will match your array indices.
Next: 7.9 Handle Object Properties, in General >>
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