The following _CastError was thrown during paint(): Null check operator used on a null value

[SeCo89]

Hi there,

I encounter this problem using this plugin:

======== Exception caught by rendering library =====================================================
The following _CastError was thrown during paint():
Null check operator used on a null value

The relevant error-causing widget was: 
  VectorTileLayer VectorTileLayer:file:///Users/xxxx/lib/UI/screens/map_page.dart:204:13
When the exception was thrown, this was the stack: 
#0      TextApproximation.renderer (package:vector_tile_renderer/src/features/text_renderer.dart:63:76)
#1      SymbolPointRenderer._preciselyOccupyLabelSpaceAtOffset (package:vector_tile_renderer/src/features/symbol_point_renderer.dart:89:22)
#2      SymbolPointRenderer._occupyLabelSpaceAtOffset (package:vector_tile_renderer/src/features/symbol_point_renderer.dart:80:12)
#3      SymbolPointRenderer.render (package:vector_tile_renderer/src/features/symbol_point_renderer.dart:56:12)
#4      FeatureDispatcher.render (package:vector_tile_renderer/src/features/feature_renderer.dart:49:16)
#5      DefaultLayer.render.<anonymous closure> (package:vector_tile_renderer/src/themes/theme_layers.dart:49:35)
#6      TileSpaceMapper.drawInTileSpace (package:vector_tile_renderer/src/features/tile_space_mapper.dart:39:7)
#7      DefaultLayer.render (package:vector_tile_renderer/src/themes/theme_layers.dart:47:31)
#8      Renderer.render.<anonymous closure> (package:vector_tile_renderer/src/renderer.dart:61:20)
#9      Timeline.timeSync (dart:developer/timeline.dart:160:22)
#10     profileSync (package:vector_tile_renderer/src/profiling.dart:16:19)
#11     Renderer.render (package:vector_tile_renderer/src/renderer.dart:38:5)
#12     VectorTilePainter.paint (package:vector_map_tiles/src/grid/tile/tile_painter.dart:50:10)
#13     _DelayCustomPainter.paint (package:vector_map_tiles/src/grid/tile/delay_painter.dart:164:17)
#14     RenderCustomPaint._paintWithPainter (package:flutter/src/rendering/custom_paint.dart:571:13)
#15     RenderCustomPaint.paint (package:flutter/src/rendering/custom_paint.dart:613:7)
#16     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#17     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:239:13)
#18     RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:144:15)
#19     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#20     PaintingContext._repaintCompositedChild (package:flutter/src/rendering/object.dart:155:11)
#21     PaintingContext.repaintCompositedChild (package:flutter/src/rendering/object.dart:98:5)
#22     PaintingContext._compositeChild (package:flutter/src/rendering/object.dart:250:7)
#23     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:231:7)
#24     RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:144:15)
#25     RenderAnimatedOpacityMixin.paint (package:flutter/src/rendering/proxy_box.dart:1080:11)
#26     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#27     PaintingContext._repaintCompositedChild (package:flutter/src/rendering/object.dart:155:11)
#28     PaintingContext.repaintCompositedChild (package:flutter/src/rendering/object.dart:98:5)
#29     PaintingContext._compositeChild (package:flutter/src/rendering/object.dart:250:7)
#30     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:231:7)
#31     RenderBoxContainerDefaultsMixin.defaultPaint (package:flutter/src/rendering/box.dart:2900:15)
#32     RenderStack.paintStack (package:flutter/src/rendering/stack.dart:654:5)
#33     RenderStack.paint (package:flutter/src/rendering/stack.dart:670:7)
#34     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#35     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:239:13)
#36     RenderBoxContainerDefaultsMixin.defaultPaint (package:flutter/src/rendering/box.dart:2900:15)
#37     RenderStack.paintStack (package:flutter/src/rendering/stack.dart:654:5)
#38     PaintingContext.pushLayer (package:flutter/src/rendering/object.dart:460:12)
#39     PaintingContext.pushClipRect (package:flutter/src/rendering/object.dart:520:7)
#40     RenderStack.paint (package:flutter/src/rendering/stack.dart:660:38)
#41     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#42     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:239:13)
#43     RenderBoxContainerDefaultsMixin.defaultPaint (package:flutter/src/rendering/box.dart:2900:15)
#44     RenderStack.paintStack (package:flutter/src/rendering/stack.dart:654:5)
#45     RenderStack.paint (package:flutter/src/rendering/stack.dart:670:7)
#46     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#47     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:239:13)
#48     RenderBoxContainerDefaultsMixin.defaultPaint (package:flutter/src/rendering/box.dart:2900:15)
#49     RenderStack.paintStack (package:flutter/src/rendering/stack.dart:654:5)
#50     RenderStack.paint (package:flutter/src/rendering/stack.dart:670:7)
#51     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#52     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:239:13)
#53     RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:144:15)
#54     RenderTransform.paint (package:flutter/src/rendering/proxy_box.dart:2617:17)
#55     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#56     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:239:13)
#57     RenderShiftedBox.paint (package:flutter/src/rendering/shifted_box.dart:84:15)
#58     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#59     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:239:13)
#60     RenderBoxContainerDefaultsMixin.defaultPaint (package:flutter/src/rendering/box.dart:2900:15)
#61     RenderStack.paintStack (package:flutter/src/rendering/stack.dart:654:5)
#62     RenderStack.paint (package:flutter/src/rendering/stack.dart:670:7)
#63     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#64     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:239:13)
#65     RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:144:15)
#66     PaintingContext.pushLayer (package:flutter/src/rendering/object.dart:460:12)
#67     PaintingContext.pushClipRect (package:flutter/src/rendering/object.dart:520:7)
#68     RenderClipRect.paint (package:flutter/src/rendering/proxy_box.dart:1554:25)
#69     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#70     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:239:13)
#71     RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:144:15)
#72     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#73     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:239:13)
#74     RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:144:15)
#75     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#76     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:239:13)
#77     RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:144:15)
#78     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#79     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:239:13)
#80     _RenderLayoutBuilder.paint (package:flutter/src/widgets/layout_builder.dart:341:15)
#81     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#82     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:239:13)
#83     RenderBoxContainerDefaultsMixin.defaultPaint (package:flutter/src/rendering/box.dart:2900:15)
#84     RenderStack.paintStack (package:flutter/src/rendering/stack.dart:654:5)
#85     RenderStack.paint (package:flutter/src/rendering/stack.dart:670:7)
#86     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#87     PaintingContext.paintChild (package:flutter/src/rendering/object.dart:239:13)
#88     RenderProxyBoxMixin.paint (package:flutter/src/rendering/proxy_box.dart:144:15)
#89     RenderObject._paintWithContext (package:flutter/src/rendering/object.dart:2796:7)
#90     PaintingContext._repaintCompositedChild (package:flutter/src/rendering/object.dart:155:11)
#91     PaintingContext.repaintCompositedChild (package:flutter/src/rendering/object.dart:98:5)
#92     PipelineOwner.flushPaint (package:flutter/src/rendering/object.dart:1116:31)
#93     RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:515:19)
#94     WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:884:13)
#95     RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:378:5)
#96     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1175:15)
#97     SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1104:9)
#98     SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:1015:5)
#99     _invoke (dart:ui/hooks.dart:148:13)
#100    PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:318:5)
#101    _drawFrame (dart:ui/hooks.dart:115:31)
The following RenderObject was being processed when the exception was fired: RenderCustomPaint#7e45c
...  parentData: <none> (can use size)
...  constraints: BoxConstraints(w=256.5, h=256.5)
...  size: Size(256.5, 256.5)
...  painter: _DelayCustomPainter#6be28()
RenderObject: RenderCustomPaint#7e45c
  parentData: <none> (can use size)
  constraints: BoxConstraints(w=256.5, h=256.5)
  size: Size(256.5, 256.5)
  painter: _DelayCustomPainter#6be28()
==================================================================================================== 

It disappears after one second, but sometimes when I reload the app, it appears again.
I know that the error occurs when you use a ! operator on a nullable instance which wasn't initialized. But initializing styledSymbol doesn't help.

Are there any suggestions?

[MendleM]

Can you share your code? I'm guessing that the style is asynchronously fetched and so it hasn't yet initialized when the map is drawn.

[SeCo89]

Thanks for the quick response. My code is very similar to the example given. Here are the relevant methods:

@override
  void initState() {
    keepAlive = widget.isSelectLocationMode ? false : true;
    _mapController = MapController();
    _popupController = PopupController();
    super.initState();
    userLocationMarkers = [];
    markers = [];
    parkingSpaces = [];
    mapZoom = widget.isSelectLocationMode
        ? AppConstants.MAX_MAP_ZOOM
            : AppConstants.MIN_MAP_ZOOM;

    _initStyle();
  }

@override
  Widget build(BuildContext context) {
    super.build(context);
    return Stack(
      children: [
        _error != null
            ? Expanded(child: Text(_error.toString()))
            : _style == null
                ? const Center(child: CircularProgressIndicator())
                : _map(),
        Helpers.getLocationProvider(context, false).hasPermission ? _locateFloatingButton() : SizedBox(),
        isLocating ? ProcessIndicatorWidget() : SizedBox(),
      ],
    );
  }

void _initStyle() async {
    try {
      _style = await _readStyle();
    } catch (e, stack) {
      // ignore: avoid_print
      print(e);
      // ignore: avoid_print
      print(stack);
      _error = e;
    }
    setState(() {});
  }

Future<Style> _readStyle() => StyleReader(
          uri: 'https://api.maptiler.com/maps/streets-v2/style.json?key={key}',
          // ignore: undefined_identifier
          apiKey: AppConstants.MAPTILER_API_KEY,
          logger: const Logger.console())
      .read();

Widget _map() => Consumer(builder: (BuildContext context, BackendService service, child) {
        return FlutterMap(
          mapController: _mapController,
          options: MapOptions(
            onMapReady: () async {
              LocationService locationService = Helpers.getLocationProvider(context, false);
              if (!widget.isSelectLocationMode) {
                locationService.isLocationRequested = true;
                positionStreamSubscription =
                await locationService.streamCurrentPosition(context, _onLocationRequested, _onLocationUpdated);
              } else {
                isLocating = false;
                if (service.addParkingSpaceKey.currentState.parkingSpace.latitude != null &&
                    service.addParkingSpaceKey.currentState.parkingSpace.longitude != null) {
                  service.updateLocationOnMap(
                    LatLng(
                      service.addParkingSpaceKey.currentState.parkingSpace.latitude,
                      service.addParkingSpaceKey.currentState.parkingSpace.longitude,
                    ),
                    true,
                  );
                } else {
                  service.updateLocationOnMap(
                    LatLng(
                      locationService.currentPosition.latitude,
                      locationService.currentPosition.longitude,
                    ),
                    true,
                  );
                }
                setParkingSpaces([
                  ParkingSpaces(
                      latitude: service.centerLocation.latitude,
                      longitude: service.centerLocation.longitude)
                ]);
                service.addParkingSpaceKey.currentState.updateView();
              }

              print('map is ready');
            },
            minZoom: AppConstants.MIN_MAP_ZOOM,
            maxZoom: AppConstants.MAX_MAP_ZOOM,
            interactiveFlags: InteractiveFlag.all & ~InteractiveFlag.rotate,
            onTap: (event, latLong) => hidePopup(),
            onPositionChanged: (mapPosition, boolValue) async {
              widget.onMapMoved(mapPosition.center);
              if (widget.isSelectLocationMode && this.markers.length > 0) {
                this.markers[0].point.latitude = mapPosition.center.latitude;
                this.markers[0].point.longitude = mapPosition.center.longitude;
              }
            },
          ),
          children: [
            VectorTileLayer(
                theme: _style.theme,
                backgroundTheme: _style.theme.copyWith(types: {ThemeLayerType.background, ThemeLayerType.fill}),
                // tileOffset: TileOffset.mapbox, enable with mapbox
                tileProviders: _style.providers),
            CurrentLocationLayer(),
            MarkerLayer(markers: userLocationMarkers),
          ],
        );
      });

     Widget _locateFloatingButton() {
    return Align(
      alignment: Alignment.bottomRight,
      child: Consumer<BackendService>(
        builder: (context, service, child) {
          return Padding(
            padding: EdgeInsets.only(
                bottom: (!(service.parkingStatus == ParkingStatus.checkingIn) && !(service.parkingStatus == ParkingStatus.checkingOut)) &&
                        !widget.isSelectLocationMode
                    ? 100.0
                    : 16.0,
                right: 16.0),
            child: (!(service.parkingStatus == ParkingStatus.checkingIn) &&
                    !(service.parkingStatus == ParkingStatus.checkingOut) &&
                    !widget.isSelectLocationMode)
                ? _locationButton()
                : SizedBox(),
          );
        },
      ),
    );
  }

The error occurs whenever the zoom value is very high. Once the map or I think style has loaded, the error disappears. if I jump to another location, the error shows again.

[SeCo89]

Do you have any suggestions??

[greensopinion]

this is fixed in version 3.1.2 of https://pub.dev/packages/vector_tile_renderer