Add a zoom slider and a GeoPoint Button on the map

home_screen.dart

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter_screenutil/flutter_screenutil.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';

class HomeScreen extends StatefulWidget {
  const HomeScreen({Key? key}) : super(key: key);

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

class _HomeScreenState extends State<HomeScreen> {
  GoogleMapController? mapController;

  CameraPosition _kInitialPosition = const CameraPosition(
    target: LatLng(19.07, 72.87),
    zoom: 15,
  );

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('GIS App'),
      ),
      body: Stack(
        children: [
          GoogleMap(
            initialCameraPosition: _kInitialPosition,
            onMapCreated: _onMapCreated,
            myLocationEnabled: true,
            myLocationButtonEnabled: false,
            mapType: MapType.hybrid,
            compassEnabled: true,
            onCameraMove: _updateCameraPosition,
            // trafficEnabled: true,
            zoomControlsEnabled: false,
          ),
          Positioned(
            bottom: 80,
            right: 15,
            child: ClipRRect(
              borderRadius: BorderRadius.circular(
                30.0,
              ),
              child: Container(
                width: 40.h,
                height: 40.h,
                color: Colors.greenAccent,
                child: IconButton(
                  padding: const EdgeInsets.all(
                    3.0,
                  ),
                  icon: const Icon(
                    Icons.pin_drop,
                    color: Colors.white,
                  ),
                  onPressed: _addGeoPoint,
                ),
              ),
            ),
          ),
          Positioned(
            bottom: 70.0,
            left: 15.0,
            child: Slider(
              inactiveColor: Colors.grey,
              activeColor: Colors.greenAccent,
              thumbColor: Colors.greenAccent,
              min: 100.0,
              max: 500.0,
              divisions: 4,
              value: radius.value,
              label: 'Radius ${radius.value}km',
              onChanged: _updateQuery,
            ),
          ),
        ],
      ),
    );
  }

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

  void _updateCameraPosition(CameraPosition position) {
    setState(() {
      _kInitialPosition = position;
    });
  }
  
    _updateQuery(value) {
    final zoomMap = {
      100.0: 12.0,
      200.0: 10.0,
      300.0: 7.0,
      400.0: 6.0,
      500.0: 5.0
    };
    final zoom = zoomMap[value];
    mapController?.moveCamera(CameraUpdate.zoomTo(zoom!));
    setState(() {
      radius.add(value);
    });
  }
}