Unsupported operation: _Namespace ERROR while using rootbundle.loadString()

Question

I am trying to use mapsforge plugin to use my own compiled map. I am not an experienced flutter developer and don't know so much about loading assets therefore can't figure out what the problem is.

File structure;

pubspec.yaml;

flutter:

  uses-material-design: true

  assets:
    - assets/login/
    - assets/maps/render_themes/
    - assets/maps/icons

Code;

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:mapsforge_flutter/core.dart';
import 'package:mapsforge_flutter/maps.dart';

class MapShow extends StatefulWidget {
  @override
  _MapShowState createState() => _MapShowState();
}

class _MapShowState extends State<MapShow> {
  late MapFile mapFile;
  late SymbolCache symbolCache;
  GraphicFactory graphicFactory = const FlutterGraphicFactory();
  DisplayModel displayModel = DisplayModel();
  late RenderThemeBuilder renderThemeBuilder;
  late String content;
  late RenderTheme renderTheme;
  late MapDataStoreRenderer jobRenderer;
  late MapModel mapModel;
  late ViewModel viewModel;

  void assignSymbolCache() async {}

  @override
  void initState() {
    super.initState();

    rootBundle
        .loadString("assets/maps/render_themes/defaultrender.xml")
        .then((String s) {
      content = s;
    });

    MapFile.from("assets/maps/akuzem.map", null, null).then((MapFile mf) {
      mapFile = mf;
    });
    symbolCache = FileSymbolCache(rootBundle);

    renderThemeBuilder =
        RenderThemeBuilder(graphicFactory, symbolCache, displayModel);

    renderThemeBuilder.parseXml(content);

    renderTheme = renderThemeBuilder.build();

    jobRenderer =
        MapDataStoreRenderer(mapFile, renderTheme, graphicFactory, true);
    mapModel = MapModel(
      displayModel: displayModel,
      renderer: jobRenderer,
    );

    viewModel = ViewModel(displayModel: displayModel);
  }

  @override
  Widget build(BuildContext context) {
    setState(() {});

    return FlutterMapView(
        mapModel: mapModel,
        viewModel: viewModel,
        graphicFactory: graphicFactory);
  }
}

Also i saw WidgetsFlutterBinding.ensureInitialized(); in an answer and added my void main() but didnt solved.

Error Showing;

Error in debug console;

Restarted application in 161ms.
Error: Unsupported operation: _Namespace
    at Object.throw_ [as throw] (http://localhost:60585/dart_sdk.js:5067:11)
    at Function.get _namespacePointer [as _namespacePointer] (http://localhost:60585/dart_sdk.js:56707:17)
    at Function._namespacePointer (http://localhost:60585/dart_sdk.js:54523:28)
    at Function._dispatchWithNamespace (http://localhost:60585/dart_sdk.js:54526:31)
    at io._File.new.exists (http://localhost:60585/dart_sdk.js:54530:23)
at readbufferfile.ReadbufferFile.new._openRaf (http://localhost:60585/packages/mapsforge_flutter/src/mapfile/readbufferfile.dart.lib.js:82:30)
    at _openRaf.next (<anonymous>)
    at runBody (http://localhost:60585/dart_sdk.js:40590:34)
    at Object._async [as async] (http://localhost:60585/dart_sdk.js:40621:7)
at readbufferfile.ReadbufferFile.new.[_openRaf] (http://localhost:60585/packages/mapsforge_flutter/src/mapfile/readbufferfile.dart.lib.js:77:20)
at readbufferfile.ReadbufferFile.new.length (http://localhost:60585/packages/mapsforge_flutter/src/mapfile/readbufferfile.dart.lib.js:93:29)
    at length.next (<anonymous>)
    at runBody (http://localhost:60585/dart_sdk.js:40590:34)
    at Object._async [as async] (http://localhost:60585/dart_sdk.js:40621:7)
at readbufferfile.ReadbufferFile.new.length (http://localhost:60585/packages/mapsforge_flutter/src/mapfile/readbufferfile.dart.lib.js:91:20)
at mapfile.MapFile.__._init (http://localhost:60585/packages/mapsforge_flutter/src/cache/memorytilebitmapcache.dart.lib.js:15605:75)
    at _init.next (<anonymous>)
    at runBody (http://localhost:60585/dart_sdk.js:40590:34)
    at Object._async [as async] (http://localhost:60585/dart_sdk.js:40621:7)
at mapfile.MapFile.__.[_init] (http://localhost:60585/packages/mapsforge_flutter/src/cache/memorytilebitmapcache.dart.lib.js:15602:20)
at from (http://localhost:60585/packages/mapsforge_flutter/src/cache/memorytilebitmapcache.dart.lib.js:15586:34)
    at from.next (<anonymous>)
    at runBody (http://localhost:60585/dart_sdk.js:40590:34)
    at Object._async [as async] (http://localhost:60585/dart_sdk.js:40621:7)
at Function.from (http://localhost:60585/packages/mapsforge_flutter/src/cache/memorytilebitmapcache.dart.lib.js:15584:20)
at map_show._MapShowState.new.initState (http://localhost:60585/packages/mapping_tool/pages/map/map_show.dart.lib.js:166:23)

Answer 1

in your initState method, you used then, It breaks your order of code.

Try this code :

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:mapsforge_flutter/core.dart';
import 'package:mapsforge_flutter/maps.dart';

class MapShow extends StatefulWidget {
  @override
  _MapShowState createState() => _MapShowState();
}

class _MapShowState extends State<MapShow> {
  late MapFile mapFile;
  late SymbolCache symbolCache;
  GraphicFactory graphicFactory = const FlutterGraphicFactory();
  DisplayModel displayModel = DisplayModel();
  late RenderThemeBuilder renderThemeBuilder;
  late String content;
  late RenderTheme renderTheme;
  late MapDataStoreRenderer jobRenderer;
  late MapModel mapModel;
  late ViewModel viewModel;

  void assignSymbolCache() async {}

  @override
  void initState() {
    super.initState();
    start();

  }

  start()async{

       ///use await let u place fields in right order
      content = await rootBundle
        .loadString("assets/maps/render_themes/defaultrender.xml");
   
    
      mapFile = await MapFile.from("assets/maps/akuzem.map", null, null);
    
    symbolCache = FileSymbolCache(rootBundle);

    renderThemeBuilder =
        RenderThemeBuilder(graphicFactory, symbolCache, displayModel);

    renderThemeBuilder.parseXml(content);

    renderTheme = renderThemeBuilder.build();

    jobRenderer =
        MapDataStoreRenderer(mapFile, renderTheme, graphicFactory, true);
    mapModel = MapModel(
      displayModel: displayModel,
      renderer: jobRenderer,
    );

    viewModel = ViewModel(displayModel: displayModel);

    ///never use set state before widget return, Do it in when your view is ready to load
    setState(() {});

   }

  @override
  Widget build(BuildContext context) {

    return FlutterMapView(
        mapModel: mapModel,
        viewModel: viewModel,
        graphicFactory: graphicFactory);
  }
}