How to set Dynamic Location or User's Location to Circle in Google Maps Flutter And also to show markers which is only inside the circle

Question

import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:flutter/material.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
import 'package:location/location.dart';
import 'package:rewahub/widgets/styles.dart';

class Gmap extends StatefulWidget {
  @override
  _GmapState createState() => _GmapState();
}

class _GmapState extends State<Gmap> {
  GoogleMapController mapController;

  LocationData _currentPosition;

  var lng, lat, loading;
  bool sitiosToggle = false;

  var sitios = [];
  Set<Marker> allMarkers = Set();

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

  Set<Circle> circles = Set.from([
    Circle(
        circleId: CircleId("myCircle"),
        radius: 500,
        center: _createCenter,
        fillColor: Color.fromRGBO(171, 39, 133, 0.1),
        strokeColor: Color.fromRGBO(171, 39, 133, 0.5),
        onTap: () {
          print('circle pressed');
        })
  ]);

  populateClients() {
    sitios = [];

    Firestore.instance.collection('retailers').getDocuments().then((docs) {
      if (docs.documents.isNotEmpty) {
        setState(() {
          sitiosToggle = true;
        });
        for (int i = 0; i < docs.documents.length; ++i) {
          initMarker(docs.documents[i].data);
        }
      }
    });
  }

  initMarker(afro) {
    allMarkers.add(Marker(
      markerId: MarkerId(afro['rname']),
      draggable: false,
      infoWindow: InfoWindow(title: afro['rname'], snippet: afro['raddress']),
      position: LatLng(afro['LatLng'].latitude, afro['LatLng'].longitude),
    ));
  }

  Set<Marker> marker = Set.from([
    Marker(
      markerId: MarkerId("mymarker"),
      alpha: 0.7,
      draggable: true,
      infoWindow: InfoWindow(title: "mymarker", snippet: "mymakrer"),
    )
  ]);

  @override
  initState() {
    loading = true;
    _getLocation();
    super.initState();
  }

  _getLocation() async {
    var location = new Location();
    try {
      _currentPosition = await location.getLocation();
      setState(() {
        lat = _currentPosition.latitude;
        lng = _currentPosition.longitude;
        loading = false;
        print(_currentPosition);
      }); //rebuild the widget after getting the current location of the user
    } on Exception {
      _currentPosition = null;
    }
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(
        primaryColor: reddish,
        primaryTextTheme: TextTheme(
          title: TextStyle(color: Colors.white),
        ),
      ),
      home: Scaffold(
        appBar: PreferredSize(
          preferredSize: Size.fromHeight(100.0),
          child: new AppBar(
            centerTitle: true,
            title: Text(
              'YOUR NEAREST STORES',
              textAlign: TextAlign.center,
            ),
          ),
        ),
        body: Stack(
          children: <Widget>[
            loading == false
                ? GoogleMap(
                    // circles: circles,
                    mapType: MapType.normal,
                    circles: circles,
                    myLocationButtonEnabled: true,
                    myLocationEnabled: true,
                    onMapCreated: _onMapCreated,
                    zoomGesturesEnabled: true,
                    compassEnabled: true,
                    scrollGesturesEnabled: true,
                    rotateGesturesEnabled: true,
                    tiltGesturesEnabled: true,
                    initialCameraPosition: CameraPosition(
                      target: LatLng(lat, lng),
                      zoom: 15.0,
                    ),
                    markers: allMarkers,
                  )
                : Center(
                    child: CircularProgressIndicator(),
                  ),
            Positioned(
                top: MediaQuery.of(context).size.height -
                    (MediaQuery.of(context).size.height - 70.0),
                right: 10.0,
                child: FloatingActionButton(
                  onPressed: () {
                    populateClients();
                  },
                  mini: true,
                  backgroundColor: Colors.red,
                  child: Icon(Icons.refresh),
                )),
          ],
        ),
      ),
    );
  }

  LatLng _createCenter() {
    return _createLatLng(lat , lng);
  }

  LatLng _createLatLng(double lat, double lng) {
    return LatLng(lat, lng);
  }
}

How to give the location of a user to circle in google maps flutter. Which means, is it able to give dynamic location to circle in google maps flutter. And also should to filter the markers inside the radius of the circle.

I am getting the error , only static variables can be initialized in the center , if i try to give dynamic location to the circle. Please help me solve this.

Thanks in advance.

Solution

You are accessing method from outside. So, it is need to be static. If you don't want so,

Move your circle initialization in initState. Like,

@override
  initState() {
    circles = Set.from([
      Circle(
          circleId: CircleId("myCircle"),
          radius: 500,
          center: _createCenter,
          fillColor: Color.fromRGBO(171, 39, 133, 0.1),
          strokeColor: Color.fromRGBO(171, 39, 133, 0.5),
          onTap: () {
            print('circle pressed');
          })
    ]);

    loading = true;
    _getLocation();
    super.initState();
  }