I am testing the virtual listview in Delphi, with the following codes:

procedure TForm1.Button1Click(Sender: TObject);
var
  Index: Integer;
begin
  for Index := 0 to 4000 do
    ListView1.Items.Count := Index;
end;

procedure TForm1.ListView1Data(Sender: TObject; Item: TListItem);
var
  DebugStr: string;
begin
  DebugStr := Format('Item.Index = %u' + #10#13, [Item.Index]);
  OutputDebugString(PChar(DebugStr));
end;

Based on my test, even if the list only shows the first several items, and do not need the data of the remaining. It will still call OnData to obtain all the data for the remaining items. Why?

Originally I think it is implemented as a lazy-load method so only when the data are required, they will be requested via OnData event.