OPtimize speed in transferring data to a listview

[rickyojr]

Is there a way to speed up the transfer the records from a recordset to a list view object?

[Serge_D]

You can use LockWindowUpdate API to stop any drawings in that ListView that will definetely will speed up the loading process. Here is an example:


private Declare Function LockWindowUpdate Lib "user32" (byval hwndLock as Long) as Long

private Sub Command1_Click()
Dim rs as new ADODB.Recordset
Dim xItem as ListItem

'I'm assuming that you already have recordset object opened
'with the appropriate records

LockWindowUpdate ListView1.hWnd

Do Until rs.EOF
set xItem = ListView1.ListItems.Add(, , rs("MyField"))
rs.MoveNext
Loop
'Unlock ListView
LockWindowUpdate 0
End Sub





Serge
Programmer Analyst
[email protected]

[Ravi Kiran]

LockWindowUpdate sometimes gives a flicker on the Desktop ( 0n WIn95), when released. (ie called with NULL )!. so check it out..

There are a couple of things you could try.
If you have set the Sorted Property to TRUE, then each time you add a item, it tries to find out the correct place it fits in the list. So, if you are going to add a lot of records in one go, it would increase speed by first set the sorted property to false, a
dd all recs in one go, and then set it to true . (the list will comeout correct anyway)

II. You can try some kind of "Background" processing. Add few records, then add more with occassionally giving up control with DOEvents. set up visual indications that you are doing so. This type of programing requires that you do it correclty. when the process is still on, you will set a flag, and every where you wil check for that flag to be on before proceesing.

A little out of place here, but i am giving some code i have at hand, which does this kind of a thing. Process a big file ( >5MB on most occasions) for Jpeg markers, and fill a list box with hits and with set of bytes after the marker:

...
nBaM = CInt(txtBytesToDisp.Text) ' no. of bytes after marker.
nl = UBound(m_cFileBuf) ' array size = file length
lstJpgMarker.Clear

nl = IIf(twobytes, nl - 1, nl) ' for two byte processing case
Screen.MousePointer = vbHourglass
for ii = 0 to nl - 1
If twobytes = false then
addit = IIf(m_cFileBuf(ii) = cMarker(0), true, false)
else
addit = IIf((m_cFileBuf(ii) = cMarker(0)) And _
(m_cFileBuf(ii + 1) = cMarker(1)), true, false)
End If
If addit then
lststr = vbNullString
nBaM = IIf(ii + nBaM > nl - 1, nl - 1 - ii, nBaM)
for jj = ii to ii + nBaM
lststr = lststr & " " & Hex$(m_cFileBuf(jj)) & " "
next jj
lstJpgMarker.AddItem txtJpgMarker.Text & "@" & Str(ii) & "," & lststr

lblNMarkers.Caption = Str(ii) & "/" & Str(nl - 1)

If lstJpgMarker.NewIndex >= 30 then
Screen.MousePointer = vbArrowHourglass
If lstJpgMarker.NewIndex Mod 10 = 0 then
DoEvents
End If
else
DoEvents
If bstopfill then Exit for
End If
End If

next ii
lblNMarkers.Caption = Str(lstJpgMarker.ListCount)
Screen.MousePointer = vbDefault
Exit Sub
...



More to point: check the bold section. First i add 30 items w/o much ado, then change the cursor to Arror + Hourglass, to indicate that things are going on in the bg ( which also would be evident by scroll bar flicker and decreasing Scroll-bar tab, anyway)
While things are being added you can scroll the list and it has "stop" support too.

This section is not 100% fool-proof ( if i close the form, while the proc. is On the program will throw-up!)


RK

[rickyojr]

Thanks I'll try It