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Briefly, we are passing in the row.
If the absolute position of the recordset is not this row,
we will move to that record. We then use the column-1 to
get the field value. In our sample project, this routine
is called 16 times, as we are displaying 8 rows and 2 columns.
As we scroll down, the 'GetItemText' event is automatically
fired.
I was a little concerned by this at
first, as scrolling up and down would generate a lot of
database activity, but in practice, it works well.
Our sample gives us another option though
- we can use 'getrows'. Use the GetRows method to copy records
from a Recordset object into a two-dimensional array. So,
instead of rs.movenext, we use…
AvarTable = rs.GetRows
This gives us a 2 dimensional array
containing all the records. Again, setting the dataview
rowcount to the number of records fires the 'GetItemText'
event. This time however, the code reads...
If IsArray(AvarTable) Then
Text = CStr(AvarTable(Column - 1, Row - 1) & "")
End If
Instead of going to the database for
the records, we are reading them from our array. This will
give us some advantages we will see later, and we will use
in our other sample project.
So, we now know how to populate the
listview. If you have had problems following my garbled
explanation of how it works, do what I did - single step
through the code. It all becomes much clearer then.
The DataViewer contains more properties
and events than the listview. ‘Hands up’ all those
who want to use 'tap and hold' in a listview. The DataViewer
supports this through context menus. Simply set the contextmenu
property to 'True', and hold down the stylus. The 'showcontextmenu'
event fires.
Private Sub dvRecs_ShowContextMenu _
(ByVal X As Long, ByVal Y As Long)
Dim hWnd As Long
Dim intSelection As Long
On Error Resume Next
hWnd = GetFocus()
intSelection = ShowPopupMenu(hWnd, X, Y)
Select Case intSelection
Case 1
Edit_Record
Case 2
If bGetRows Then
MsgBox "Delete record: " _
& CStr(AvarTable(0, _
dvRecs.Selection - 1) & "")
Else
MsgBox "Delete record: " _
& GetRecordsetFieldValue _
(rs, SaveRow, SaveCol)
End If
Case 3
Total_Records
Case Else
End Select
frmMain.SetFocus
dvwRecords.SetFocus
End Sub
Public Function ShowPopupMenu(hWnd As
Long, _
Left As Integer, Top As Integer) _
As Integer
Dim hMenu As Long
Dim lOption As Long
Dim iMenuItem As Integer
hMenu = CreatePopupMenu()
' Edit menu items
lOption = MF_ENABLED
AppendMenu hMenu, lOption Or MF_STRING, 1, _
"Edit"
AppendMenu hMenu, lOption Or MF_STRING, 2, _
"Delete"
AppendMenu hMenu, lOption Or MF_STRING, 3, _
"Total Records"
ShowPopupMenu = (TrackPopupMenuEx(hMenu, _
TPM_LEFTALIGN Or TPM_TOPALIGN _
Or TPM_RETURNCMD, Left / 15, _
Top / 15, hWnd, 0))
DestroyMenu hMenu
End Function
This will give us a context menu with
3 items, Edit, Delete and Total Records on it. To demonstrate
the use of Edit, we simply move the data from our data viewer
to our text fields, and make the frame visible. The 'OK'
button simply makes the frame invisible, but could easily
write back any changes to our record.
Delete records is a dummy item, but
Total records allows us to get a total of the numeric fields
in the DataViewer. This explains why we used the 'getrows'
method earlier. To total up using the normal method of 'movenext',
we need to use the procedure GetRecordsetFieldValue, which
may (most probably will) involve reading records from the
database. If we use 'getrows', we can simply total up using
our array. Using the emulator, it takes approx 50 milliseconds.
Using 'movenext' it takes approx 850 milliseconds to total
up. This was using 1000 records.
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