Can we fill color for countries in google_maps_flutter?

Question

I'm implementing the google_maps_flutter plugin in my flutter app and stucked in highlighting the country for example India by red color, Australia by blue etc. I went throught geoJson but not sure how to implement it in flutter.

Thanks in advance.

Answer 1

After spending 4 days in looking into map stuff and it's features I got most easy and feasible solution for filling any country, state, continent in flutter. We can get the geoJson data of any region from here

Extract the latLong co-ordinates of that region and draw a polygon based on it.

Following is the code for filling India with colour.

GeoJson.dart

class GeoJson
{
 static const List IN = [
   [77.83745079947457,35.494009507787766],[78.91226891471322,34.32193634697579],
   [78.81108646028574,33.50619802503242],[79.20889163606857,32.994394639613716],
   [79.17612877799553,32.48377981213771],[78.45844648632601,32.61816437431273],
   [78.73889448437401,31.515906073527063],[79.7213668151071,30.882714748654728],
   [81.11125613802932,30.183480943313402],[80.4767212259174,29.72986522065534],
   [80.08842451367627,28.79447011974014],[81.05720258985203,28.416095282499043],
   [81.99998742058497,27.925479234319994],[83.30424889519955,27.36450572357556],
   [84.6750179381738,27.234901231387536],[85.25177859898338,26.72619843190634],
   [86.02439293817918,26.63098460540857],[87.22747195836628,26.397898057556077],
   [88.06023766474982,26.41461538340249],[88.17480431514092,26.81040517832595],
   [88.04313276566123,27.445818589786825],[88.12044070836987,27.876541652939594],
   [88.73032596227856,28.086864732367516],[88.81424848832054,27.29931590423936],
   [88.83564253128938,27.098966376243762],[89.74452762243884,26.719402981059957],
   [90.37327477413407,26.87572418874288],[91.21751264848643,26.808648179628022],
   [92.03348351437509,26.83831045176356],[92.10371178585973,27.452614040633208],
   [91.69665652869668,27.77174184825166],[92.50311893104364,27.89687632904645],
   [93.41334760943268,28.640629380807226],[94.56599043170294,29.277438055939985],
   [95.40480228066464,29.03171662039213],[96.11767866413103,29.452802028922466],
   [96.58659061074749,28.830979519154344],[96.24883344928779,28.41103099213444],
   [97.32711388549004,28.26158274994634],[97.40256147663612,27.88253611908544],
   [97.0519885599681,27.69905894623315],[97.1339990580153,27.083773505149964],
   [96.41936567585097,27.264589341739224],[95.12476769407496,26.5735720891323],
   [95.1551534362626,26.001307277932085],[94.60324913938538,25.162495428970402],
   [94.55265791217164,24.675238348890332],[94.10674197792505,23.85074087167348],
   [93.3251876159428,24.078556423432204],[93.28632693885928,23.043658352139005],
   [93.06029422401463,22.70311066333557],[93.16612755734836,22.278459580977103],
   [92.67272098182556,22.041238918541254],[92.14603478390681,23.627498684172593],
   [91.86992760617132,23.624346421802784],[91.70647505083211,22.985263983649183],
   [91.15896325069971,23.50352692310439],[91.46772993364367,24.072639471934792],
   [91.91509280799443,24.13041372323711],[92.37620161333481,24.976692816664965],
   [91.79959598182207,25.147431748957317],[90.8722107279121,25.132600612889547],
   [89.92069258012185,25.26974986419218],[89.83248091019962,25.96508209889548],
   [89.35509402868729,26.014407253518073],[88.56304935094977,26.44652558034272],
   [88.2097892598025,25.76806570078271],[88.93155398962308,25.238692328384776],
   [88.30637251175602,24.866079413344206],[88.08442223506242,24.501657212821925],
   [88.69994022009092,24.23371491138856],[88.52976972855377,23.631141872649163],
   [88.87631188350309,22.879146429937826],[89.03196129756623,22.055708319582976],
   [88.88876590368542,21.690588487224748],[88.20849734899521,21.703171698487807],
   [86.97570438024027,21.49556163175521],[87.03316857294887,20.743307806882413],
   [86.49935102737378,20.151638495356607],[85.0602657409097,19.4785788029711],
   [83.94100589390001,18.302009792549725],[83.18921715691785,17.67122142177898],
   [82.19279218946592,17.016636053937813],[82.19124189649719,16.556664130107848],
   [81.69271935417748,16.310219224507904],[80.79199913933014,15.951972357644491],
   [80.32489586784388,15.899184882058348],[80.02506920768644,15.136414903214147],
   [80.2332735533904,13.835770778859981],[80.28629357292186,13.006260687710833],
   [79.8625468281285,12.056215318240888],[79.85799930208682,10.35727509199711],
   [79.340511509116,10.30885427493962],[78.88534549348918,9.546135972527722],
   [79.18971967968828,9.216543687370148],[78.2779407083305,8.933046779816934],
   [77.94116539908435,8.252959092639742],[77.53989790233794,7.965534776232333],
   [76.59297895702167,8.89927623131419],[76.13006147655108,10.299630031775521],
   [75.74646731964849,11.308250637248307],[75.39610110870957,11.781245022015824],
   [74.86481570831681,12.741935736537897],[74.61671715688354,13.99258291264968],
   [74.44385949086723,14.617221787977696],[73.5341992532334,15.99065216721496],
   [73.11990929554943,17.928570054592498],[72.82090945830865,19.208233547436166],
   [72.8244751321368,20.419503282141534],[72.6305334817454,21.356009426351008],
   [71.17527347197395,20.757441311114235],[70.4704586119451,20.877330634031384],
   [69.16413008003883,22.0892980005727],[69.64492760608239,22.450774644454338],
   [69.34959679553435,22.84317963306269],[68.1766451353734,23.69196503345671],
   [68.84259931831878,24.35913361256094],[71.04324018746823,24.3565239527302],
   [70.84469933460284,25.21510203704352],[70.28287316272558,25.72222870533983],
   [70.16892662952202,26.491871649678842],[69.51439293811312,26.940965684511372],
   [70.61649620960193,27.989196275335868],[71.77766564320032,27.913180243434525],
   [72.8237516620847,28.961591701772054],[73.45063846221743,29.97641347911987],
   [74.42138024282026,30.979814764931177],[74.40592898956501,31.69263947196528],
   [75.25864179881322,32.2711054550405],[74.45155927927871,32.7648996038055],
   [74.10429365427734,33.44147329358685],[73.74994835805195,34.31769887952785],
   [74.24020267120497,34.74888703057125],[75.75706098826834,34.50492259372132],
   [76.87172163280403,34.65354401299274],[77.83745079947457,35.494009507787766]];
}

main.dart

 @override
  void initState() {
    addPoints();
    List< Polygon > addPolygon = [
      Polygon(
        polygonId: PolygonId( 'India' ),
        points: point,
        consumeTapEvents: true,
        strokeColor: Colors.grey,
        strokeWidth: 1,
        fillColor: Colors.redAccent,
      ),
    ];
    polygon.addAll( addPolygon );

    super.initState();
  }

void addPoints()
 {
   for( var i=0 ; i < GeoJson.IN.length ; i++ )
   {
     var ltlng= LatLng( GeoJson.IN[ i ][ 1 ], GeoJson.IN[ i ][ 0 ] );
     point.add( ltlng );
   }
 }

 void _onMapCreated(GoogleMapController controller)
 {
   mapController = controller;
 }

Widget mapState()
 {
   return GoogleMap(
     onMapCreated: _onMapCreated,
     initialCameraPosition: CameraPosition(
         target: _center,
         zoom: 0.0
     ),
     scrollGesturesEnabled: true,
     zoomGesturesEnabled: true,
     myLocationButtonEnabled: false,
     gestureRecognizers: Set()
       ..add( Factory<PanGestureRecognizer>(() => PanGestureRecognizer())),
     //markers: markers,
     polygons: polygon,
   );
 }

Answer 2

For anyone wondering - here is the full main.dart code that can be copy & pasted in order to work. Make sure to add your API key for google maps under android/app/src/main/AndroidManifest.xml.

Lastly add the geojson.dart as described above.

    import 'package:flutter/foundation.dart';
    import 'package:flutter/gestures.dart';
    import 'package:flutter/material.dart';
    import 'package:google_maps_flutter/google_maps_flutter.dart';
    import 'geojson.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 {
      Set polygon = new Set();
    
      List point = [];
    
    
      GoogleMapController mapController;
    
      @override
      void initState() {
        addPoints();
        List addPolygon = [
          Polygon(
            polygonId: PolygonId( 'India' ),
            points: point,
            consumeTapEvents: true,
            strokeColor: Colors.grey,
            strokeWidth: 1,
            fillColor: Colors.redAccent,
          ),
        ];
        polygon.addAll( addPolygon );
    
        super.initState();
      }
    
      void addPoints()
      {
        for( var i=0 ; i (() => PanGestureRecognizer())),
          //markers: markers,
          polygons: polygon,
        );
      }
    
      @override
      Widget build(BuildContext context) {
        // TODO: implement build
        return mapState();
    
      }
    }