Die Reihenfolge passt nicht. Versuchs doch mal so:
Delphi-Quellcode:
procedure TTabbedForm.CornerButton1Click(Sender: TObject);
var Plg : TMapPolygonDescriptor;
Outline : System.TArray<TMapCoordinate>;
begin
SetLength(Outline,5);
Outline[0]:=TMapCoordinate.Create(51.35619, 12.58328);
Outline[1]:=TMapCoordinate.Create(51.35620, 12.58328);
Outline[2]:=TMapCoordinate.Create(51.35620, 12.58329);
Outline[3]:=TMapCoordinate.Create(51.35619, 12.58329);
Outline[4]:=TMapCoordinate.Create(51.35619, 12.58328);
Plg:=TMapPolygonDescriptor.Create(Outline);
MapView1.AddPolygon(Plg);
end;