ArcGIS Runtime100.3 加载离线tpk不显示

                Map myMap = new Map();

                var FilePath = Path.Combine(Android.OS.Environment.ExternalStorageDirectory.ToString(), "FieldSurvey", "JY-H-22.tpk");

                ArcGISTiledLayer tileLayer = new ArcGISTiledLayer(new Uri(FilePath));

                //TileCache tpkcache = new TileCache(FilePath);

                // await tpkcache.LoadAsync();//看到有人加了这一句报错，我加上了后也报错no data

                //ArcGISTiledLayer tileLayer = new ArcGISTiledLayer(tpkcache);

                myMap.Basemap.BaseLayers.Add(tileLayer);

                _myMapView.Map = myMap;

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