FMX TGrid OnGetValue after column moving - delphi

Question

I have Grid with enabled columns moving, and code:
type
TRec = record
Col0,
Col1,
Col2: string;
end;
var
Data: TArray<TRec>;
procedure TFormMain.GridGetValue(Sender: TObject; const Col, Row: Integer; var Value: TValue);
begin
case Col of
0: Value := Data[Row].Col0;
1: Value := Data[Row].Col1;
2: Value := Data[Row].Col2;
end;
end;
When column is moved this OnGetValue code works incorrectly (shown columns data on the previous positions). How to fix this? Should I use OnColumnMoved event and remember new columns position manually?

Answer 1

Ok, this is my own answer:
We should add helper function to our TRec for reading fields by index:
type
TRec = record
Col0,
Col1,
Col2: string;
function GetField(AIndex: Integer): string;
end;
function TRec.GetField(AIndex: Integer): string;
begin
case AIndex of
0: Result := Col0;
1: Result := Col1;
2: Result := Col2;
else
Result := '';
end;
end;
Also 2 functions to save and restore TGrid columns using Ini file:
type
TColumnData = record
Pos: UInt8;
Visible: Boolean;
Width: UInt16;
end;
procedure LoadColumns(AGrid: TGrid; const ASection, AIdent: string);
var
I, J, ColsSize: Integer;
A: TArray<TColumnData>;
Col: TColumn;
begin
for I := 0 to AGrid.ColumnCount - 1 do
AGrid.Columns[I].Tag := I;
SetLength(A, AGrid.ColumnCount);
ColsSize := AGrid.ColumnCount*SizeOf(TColumnData);
if ReadIni(<FileName>, ASection, AIdent, (#A[0])^, ColsSize) = ColsSize then
for J := 0 to AGrid.ColumnCount - 1 do begin
for I := 0 to AGrid.ColumnCount - 1 do begin
Col := AGrid.Columns[I];
if Col.Tag = A[J].Pos then begin
Col.Index := J;
Col.Visible := A[J].Visible;
Col.Width := A[J].Width;
end;
end;
end;
end;
procedure SaveColumns(AGrid: TGrid; const ASection, AIdent: string);
var
I, ColsSize: Integer;
A: TArray<TColumnData>;
Col: TColumn;
begin
SetLength(A, AGrid.ColumnCount);
ColsSize := AGrid.ColumnCount*SizeOf(TColumnData);
for I := 0 to AGrid.ColumnCount - 1 do begin
Col := AGrid.Columns[I];
A[I].Pos := Col.Tag;
A[I].Visible := Col.Visible;
A[I].Width := Round(Col.Width);
end;
WriteIni(<FileName>, ASection, AIdent, (#A[0])^, ColsSize);
end;
Now we should call LoadColumns (which is also initialize Tag fields for Columns) from OnFormCreate and SaveColumns from OnFormDestroy. And finally OnGetValue code:
var
Data: TArray<TRec>;
procedure TFormMain.GridGetValue(Sender: TObject; const Col, Row: Integer; var Value: TValue);
begin
Value := Data[Row].GetField((Sender as TGrid).Columns[Col].Tag);
end;