Google Maps Web throws type error on adding polyline

[SirLink]

Adding a Polyline to the map throws a type error
errors.dart:163 Uncaught (in promise) Error: Expected a value of type 'List<LatLng>', but got one of type 'List<dynamic>'

The problem seems to be in this code on Convert.dart line 321
points: rawPolyline['points'] ?.map((rawPoint) => LatLng.fromJson(rawPoint)) ?.toList(),

I managed to fix it by adding a type to the map and i can now see the polyline painted on the map, though it has a default color and i can't seem to be able to change it

points: rawPolyline['points'] ?.map<LatLng>((rawPoint) => LatLng.fromJson(rawPoint)) ?.toList(),

[darshankawar]

Hi @SirLink,
Please provide flutter doctor -v, a minimal complete reproducible code sample along with pubspec.yaml that shows the issue.
Thanks.

[SirLink]

Hello @darshankawar , sure
You need to run this on the web

import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:quartet/quartet.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.
        primarySwatch: Colors.blue,
        // This makes the visual density adapt to the platform that you run
        // the app on. For desktop platforms, the controls will be smaller and
        // closer together (more dense) than on mobile platforms.
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);

  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  List<Polyline> polylines = List();

  @override
  void initState() {
    List<LatLng> result = decodePolyline("wezu@vcgdNf@CG_BGwACGE?GAGI?IMQYQaAS");
    final PolylineId polylineId = PolylineId("1");
    final Polyline polyline = Polyline(
      polylineId: polylineId,
      consumeTapEvents: true,
      color: Colors.blue,
      width: 5,
      points: result,
    );
    polylines.add(polyline);
    super.initState();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          // Here we take the value from the MyHomePage object that was created by
          // the App.build method, and use it to set our appbar title.
          title: Text(widget.title),
        ),
        body: GoogleMap(
            polylines: polylines.toSet(),
            initialCameraPosition:
                CameraPosition(target: LatLng(8.98668, -79.50412),zoom: 18)));
  }
}

List<LatLng> decodePolyline(String encoded){
  List<LatLng> poly = [];
  int index = 0, len = encoded.length;
  int lat = 0, lng = 0;


  while (index < len) {
    int b, shift = 0, result = 0;
    do {
      b = codePointAt(encoded, index++) - 63;
      result |= (b & 0x1f) << shift;
      shift += 5;
    } while (b >= 0x20);
    int dlat = ((result & 1) != 0 ? -(result >> 1) : (result >> 1));
    lat += dlat;

    shift = 0;
    result = 0;
    do {
      b = codePointAt(encoded, index++) - 63;
      result |= (b & 0x1f) << shift;
      shift += 5;

    } while (b >= 0x20);

    int dlng = ((result & 1) != 0 ? -(result >> 1) : (result >> 1));

    lng += dlng;

    LatLng p =
    new LatLng((lat / 1E5).toDouble(), (lng / 1E5).toDouble());
    poly.add(p);
  }
  return poly;
}

[√] Flutter (Channel beta, 1.21.0-9.2.pre, on Microsoft Windows [Versión 10.0.19041.450], locale es-PE)
    • Flutter version 1.21.0-9.2.pre at C:\src\flutter
    • Framework revision 81a45ec2e5 (8 days ago), 2020-08-27 14:14:33 -0700
    • Engine revision 20a9531835
    • Dart version 2.10.0 (build 2.10.0-7.3.beta)


[√] Android toolchain - develop for Android devices (Android SDK version 30.0.0)
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    • Platform android-30, build-tools 30.0.0
    • Java binary at: C:\Program Files\Android\Android Studio\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)
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[√] Android Studio (version 4.0)
    • Android Studio at C:\Program Files\Android\Android Studio
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    • Dart plugin version 193.7547
    • Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b01)

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[√] Connected device (3 available)
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• No issues found!

[darshankawar]

H @SirLink,
There's similar open issue related to adding polyline, 65152.
Please follow-up there for updates and any questions.
Closing this as duplicate. If you disagree, write in comments and I'll reopen.
Thanks.

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