How to prevent dragging columns on a Firemonkey grid?

Question

Is there a way to prevent column header dragging (re-ordering) on a FireMonkey 2 TGrid?

The THeader instance is private to the TGrid class, and I can't find any other property that controls this. The default of THeaderItem.DragMode is dmAutomatic (for some unfathomable reason).

Short of creating a new TGrid descendant, or breaking the THeader out of the grid, I can't see how to get DragMode back to dmManual.

Answer 1

You can access the FHeader private field using the RTTI, and from here you can write a method to set the DragMode of the Headers.

Try this code

procedure SetHeaderDragMode(Grid : TGrid; DragMode:TDragMode);
Var
  LCtx  : TRttiContext;
  LType : TRttiType;
  LField: TRttiField;
  LHeader: FMX.Grid.THeader;
  i : Integer;
begin
  LCtx:=TRttiContext.Create;
  LType:=LCtx.FindType('FMX.Grid.TGrid');
  if (LType<>nil) then
   LField:=  LType.GetField('FHeader');

  if (LField<>nil) then
  begin
    LHeader:=THeader(LField.GetValue(Grid).AsObject);
    if LHeader<>nil then
      for i:=0 to  LHeader.Count-1 do
        LHeader.Items[i].DragMode:=DragMode;
  end;
end;

And use like so

 SetHeaderDragMode(Grid1,TDragMode.dmManual);