Thanks to your support, examples, info and code that you suggested, I was able to sort my listboxes using RowComparision. However, I noticed that in lists where there are several hundred rows the sorting is slow, it takes even several seconds to sort. Can the code be improved or some trick used to speed up the execution?
I also tried with this, but the substance does not change.
Select Case column
Case 3 'colonne con il tipo DATA
Var n1 As DateTime
Var n2 As DateTime
Var olds As String
Var lc As New locale("it-IT")
if Me.CellTextAt(row1,column)<>"" then
olds = Me.CellTextAt(row1,column)
n1 = datetime.FromString(olds, lc)
if Me.CellTextAt(row2,column)<>"" then
olds = Me.CellTextAt(row2,column)
n2= datetime.FromString(olds, lc)
If N1 < N2 Then
result = -1
ElseIf N1 > N2 Then
result = 1
Else
result = 0
End If
end if
end if
Return True
Else 'nulla, esco
Return False
End select
I also tried with this, but the substance does not change.
if you add a row to a list you should get the row index. (all cells are currently strings, unfortunately)
if you fill the list (without datasource) put a datetime object in the celltag.
you already used the string to datetime convert.
for empty string use nil.
More like: DesktopListbox.CellTagAt(row, column) = DateTime Object taken from Source Data
Not at my Dev.Desk currently. But the comparison will then look something like this:
If Me.CellTagAt(row1,column) <> Nil Then
If Me.CellTagAt(row1,column).DateTimeValue < Me.CellTagAt(row2,column).DateTimeValue Then
result = -1
ElseIf Me.CellTagAt(row1,column).DateTimeValue > Me.CellTagAt(row2,column).DateTimeValue Then
result = 1
Else
result = 0
End If
Return True
Else
Return False
End Select
Asked ages back in the original post.
Comes from a database.
Attempts to get the data sorted at the query stage (which should surely be the fastest route?) floundered and the OP elected to continue down the RowComparison route.
Yet another solution could be to put the SQLDate formatted text into the cell, but to paint the text in the celltextpaint event using localised formatting, for that column.
Simply clicking the list header would then sort the list happily without using either RowComparison or a database requery.
Pull the Data from the Database in a Format that can be sorted by the Listbox without further handling in RowComparison.
Put the sortable Text into the ListBox.CellTexts but handle the drawing of the CellText by your Code in the PaintCellText.Event.
PaintCellText:
Select Case column
Case 0
g.DrawingColor = &c000000
g.DrawText(DateTime.FromString(Me.CellTextAt(row,column)).ToString(DateTime.FormatStyles.Long, DateTime.FormatStyles.None), x, y, g.Width, True)
Return True
End Select
But once you have the date string you can use it to create a datetime object and thus get the SecondsFrom1970 property, and store that instead in the tag. This may take more time in loading but the sorting then becomes quick.
At start the App adds 10.001 random dates and writes them into the Listbox (so, in random roder).
Then a Message Box appears just before the Listbox will be sorted, just to se how long sorting 10.0000 Lines will take with a standard Listbox.
(Disable VerticalScrollbar before adding this much lines to a Listbox on Screen, in Xojo before 2024.4.) - Look here why.
I would like to try sorting, formatting the date in PaintCellTEXt, but I get an error, again due to formatting.: date needs to be in the format of YYYY-MM-DD HH:MM or YYYY-MM-DD
I have the upload part of my listbox where I enter the data like this:
Dim DataFormattata as date
While Not Rows.AfterLastRow
......
ListBoxRicerca.AddRow(....rows2.Column("Data").DateTimeValue.SQLDate)
rows.MoveToNextRow
..............
Wend
rows.Close
And already here I don’t understand why the date is formatted as 2024-05-21 for me while in Sascha S’s example it comes out formatted as “21 May 2024”.
I noticed that, by deleting the line from the original project, everything still works. So, I also delete it from mine and it gives me the error on the line before … in g.DrawText… telling me: Parse error: date needs to be in the format of YYYY-MM-DD HH:MM or YYYY-MM-DD
May it be possible that your querry delivers data points with NIL values? That may cause the Parse errors, maybe.
My example writes YYYY-MM-DD values into the CellText properties. But in the PaintCellText event it replaces the drawing of the CellTexts as they are and replaces them with a drawing formatted as “21 May 2024”. And because the CellText is formatted as YYYY-MM-DD but just displayed formatted as “21 May 2024”, the ListBox can use the normal alphanumeric sorting algorithm.
In fact your example is fantastic and I think it can solve my problem in display speed… but unfortunately I have this problem and I can’t understand why, I try to see if there are NIL date values
Try
g.DrawText(DateTime.FromString(Me.CellTextAt(row,column)).ToString(DateTime.FormatStyles.Long, DateTime.FormatStyles.None), x, y, g.Width, True)
Catch err As RuntimeException
g.DrawText("", x, y, g.Width, True)
End Try
(Catching all RuntimeException’s is not recommended and should be handled in the UnhandledException Event of the App Object, but here it’s ok…)
