Saving and reloading Polygons in FNCGoogleMaps

FNC TMS FNC Maps
1

I want a user in a Delphi VCL application to be able to create a Polygon in FNCGoogleMaps, modify it and then save it to a database so that it can be reloaded at a later date. I can create, modify and save it as a string of JSONArray using the AEventData.CustomData on the OnPolyElementEditEnd event. Is there any way of loading this JSONArray straight into a FNCMapsPolygon or FNCMapsCoordinateRecArray or do i have to parse it before loading it into a FNCMapsCoordinateRecArray?

Any help would be appreciated. Tim

2

Hi,

Yes, it requires some additional class wrapping, but here is the code.

type
  TCoordinateList = class(TObjectList<TTMSFNCMapsCoordinateItem>, ITMSFNCBaseListIO, ITMSFNCBasePersistenceIO)
  private
    FOwnerInterface: IInterface;
  protected
    function GetItemClass: TClass;
    function CreateObject(const AClassName: string; const ABaseClass: TClass): TObject;

    { IInterface }
    function _AddRef: Integer; stdcall;
    function _Release: Integer; stdcall;
  public
    function QueryInterface(const IID: TGUID; out Obj): HResult; virtual; stdcall;
  end;

procedure TForm1.TMSFNCGoogleMaps1PolyElementEditEnd(Sender: TObject;
  AEventData: TTMSFNCMapsEventData);
var
  p: TTMSFNCGoogleMapsPolyline;
  a: TCoordinateList;
  I: Integer;
begin
  if Assigned(AEventData.PolyElement) then
  begin
    if (AEventData.PolyElement is TTMSFNCGoogleMapsPolyline) then
    begin
      p := (AEventData.PolyElement as TTMSFNCGoogleMapsPolyline);
      a := TCoordinateList.Create;
      a.JSON := AEventData.CustomData;

      TMSFNCGoogleMaps1.BeginUpdate;

      try
        p.Recreate := True;
        p.Coordinates.Clear;
        for I := 0 to a.Count - 1 do
          p.Coordinates.Add.Assign(a[I]);

        TTMSFNCUtils.Log(p.Coordinates.JSON);
      finally
        a.Free;
      end;

      TMSFNCGoogleMaps1.EndUpdate;
    end;
  end;
end;

{ TCoordinateList }


function TCoordinateList.CreateObject(const AClassName: string;
  const ABaseClass: TClass): TObject;
begin
  Result := TTMSFNCMapsCoordinateItem.Create(nil);
end;

function TCoordinateList.GetItemClass: TClass;
begin
  Result := TTMSFNCMapsCoordinateItem;
end;


function TCoordinateList._AddRef: Integer;
begin
  if FOwnerInterface <> nil then
    Result := FOwnerInterface._AddRef else
    Result := -1;
end;


function TCoordinateList._Release: Integer;
begin
  if FOwnerInterface <> nil then
    Result := FOwnerInterface._Release else
    Result := -1;
end;


function TCoordinateList.QueryInterface(const IID: TGUID;
  out Obj): HResult;
const
  E_NOINTERFACE = HResult($80004002);
begin
  if GetInterface(IID, Obj) then Result := 0 else Result := E_NOINTERFACE;
end;
3

Pieter

Thank you for that but I think there is something wrong. I do not believe that TCoordinateList has a JSON property as a.JSON is an error. As i could not get this to work i was not able to progress with testing but what i had hoped for was something like:

procedure TFormBoundary.TMSFNCGoogleMaps1PolyElementEditEnd(Sender: TObject;
AEventData: TTMSFNCMapsEventData);
var p: TTMSFNCGoogleMapsPolyline;
a: TCoordinateList;
I: Integer;
begin
if Assigned(AEventData.PolyElement) then
begin
try
tblData.edit;
tblData['PolygonBoundary'] := AEventData.CustomData;
tblData.Post;
finally

end;

end;
end;

procedure TFormBoundary.LoadBoundary;
var aData : String;
ca : TTMSFNCMapsCoordinateRecArray;
pg: TTMSFNCGoogleMapsPolygon;
begin
if tblData['PolygonBoundary'] <> null then
begin
aData := tblData['PolygonBoundary'];
ca.LoadJSON(aData); // To be replaced with routine
TMSFNCGoogleMaps1.BeginUpdate;
pg := TTMSFNCGoogleMapsPolygon(TMSFNCGoogleMaps1.AddPolygon(ca));
pg.Editable := true;
pg.StrokeColor := clRed;
pg.StrokeWidth := 2;
TMSFNCGoogleMaps1.EndUpdate;
end;

end;

4

My apologies for the above formatting. Something went wrong as i copied it.

5

JSON is a property that is available when FMX.TMSFNCTypes unit is added. You will also need to add FMX.TMSFNCPersistence unit.