The issue concerning the error when displaying the map widget while getting the user current location is that, getting the user's actual current location is an asynchronous operation and thus the during that whole process initial position will be null thus we make a conditional that runs as we wait for the async operation to complete then display the map when then the value will be non-null. I have refactored the code and used the geolocator package instead
import 'package:flutter/cupertino.dart';
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:geolocator/geolocator.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
class Map extends StatefulWidget {
@override
_MapState createState() => _MapState();
}
class _MapState extends State<Map> {
Completer<GoogleMapController> controller1;
//static LatLng _center = LatLng(-15.4630239974464, 28.363397732282127);
static LatLng _initialPosition;
final Set<Marker> _markers = {};
static LatLng _lastMapPosition = _initialPosition;
@override
void initState() {
super.initState();
_getUserLocation();
}
void _getUserLocation() async {
Position position = await Geolocator().getCurrentPosition(desiredAccuracy: LocationAccuracy.high);
List<Placemark> placemark = await Geolocator().placemarkFromCoordinates(position.latitude, position.longitude);
setState(() {
_initialPosition = LatLng(position.latitude, position.longitude);
print('${placemark[0].name}');
});
}
_onMapCreated(GoogleMapController controller) {
setState(() {
controller1.complete(controller);
});
}
MapType _currentMapType = MapType.normal;
void _onMapTypeButtonPressed() {
setState(() {
_currentMapType = _currentMapType == MapType.normal
? MapType.satellite
: MapType.normal;
});
}
_onCameraMove(CameraPosition position) {
_lastMapPosition = position.target;
}
_onAddMarkerButtonPressed() {
setState(() {
_markers.add(
Marker(
markerId: MarkerId(_lastMapPosition.toString()),
position: _lastMapPosition,
infoWindow: InfoWindow(
title: "Pizza Parlour",
snippet: "This is a snippet",
onTap: (){
}
),
onTap: (){
},
icon: BitmapDescriptor.defaultMarker));
});
}
Widget mapButton(Function function, Icon icon, Color color) {
return RawMaterialButton(
onPressed: function,
child: icon,
shape: new CircleBorder(),
elevation: 2.0,
fillColor: color,
padding: const EdgeInsets.all(7.0),
);
}
@override
Widget build(BuildContext context) {
return Scaffold(
body: _initialPosition == null ? Container(child: Center(child:Text('loading map..', style: TextStyle(fontFamily: 'Avenir-Medium', color: Colors.grey[400]),),),) : Container(
child: Stack(children: <Widget>[
GoogleMap(
markers: _markers,
mapType: _currentMapType,
initialCameraPosition: CameraPosition(
target: _initialPosition,
zoom: 14.4746,
),
onMapCreated: _onMapCreated,
zoomGesturesEnabled: true,
onCameraMove: _onCameraMove,
myLocationEnabled: true,
compassEnabled: true,
myLocationButtonEnabled: false,
),
Align(
alignment: Alignment.topRight,
child: Container(
margin: EdgeInsets.fromLTRB(0.0, 50.0, 0.0, 0.0),
child: Column(
children: <Widget>[
mapButton(_onAddMarkerButtonPressed,
Icon(
Icons.add_location
), Colors.blue),
mapButton(
_onMapTypeButtonPressed,
Icon(
IconData(0xf473,
fontFamily: CupertinoIcons.iconFont,
fontPackage: CupertinoIcons.iconFontPackage),
),
Colors.green),
],
)),
)
]),
),
);
}
}
Best Answer
If you allow me, I would suggest a different approach to this problem. I think in the current version of google maps for Flutter (0.4.0) you don't have a method to get the new position after dragging the marker, so my solution was to use the camera position to move the marker around and then use the current camera position to get the new coordinates. So in your code, you could do something like this:
Then you can set your marker's new state each time the user moves the camera around and use this coordinates for any other purpose you need:
I hope it helps!