我收到的是Positions流，然后更新一个_position变量，该变量在center:中用于设置地图位置，在Marker中用于显示用户位置。
问题在于标记会更新，但地图位置不会更新。
预期的行为是，当地图在其下方移动时，标记始终保持在屏幕中央，但是情况恰恰相反。你能看到我把事情弄错了吗？
非常感谢您的时间和帮助。
class HomeScreen extends StatefulWidget {
final String name;
HomeScreen({
Key key,
@required this.name,
}) : super(key: key);
@override
_HomeScreenState createState() => _HomeScreenState();
}
class _HomeScreenState extends State<HomeScreen> {
Geolocator _geolocator;
Position _position;
FlutterMap _flutterMap;
MapOptions _mapOptions;
MapController _controller;
void checkPermission() {
_geolocator.checkGeolocationPermissionStatus().then((status) {
print('status: $status');
});
_geolocator
.checkGeolocationPermissionStatus(
locationPermission: GeolocationPermission.locationAlways)
.then((status) {
print('always status: $status');
});
_geolocator.checkGeolocationPermissionStatus(
locationPermission: GeolocationPermission.locationWhenInUse)
..then((status) {
print('whenInUse status: $status');
});
}
@override
void initState() {
super.initState();
_geolocator = Geolocator();
checkPermission();
updateLocation();
}
void setMap() {
_controller = MapController();
_mapOptions = MapOptions(
center: LatLng(_position.latitude, _position.longitude),
minZoom: 16.0,
maxZoom: 19.0,
);
_flutterMap = FlutterMap(
options: _mapOptions,
mapController: _controller,
layers: [
// PolygonLayer(polygonOpts, map, stream)
// PolygonLayerOptions(
// polygons:
// ),
TileLayerOptions(
// urlTemplate:'https://api.openrouteservice.org/mapsurfer/{z}/{x}/{y}.png?api_key=5b3ce3597851110001cf62484c4b65d85bc844eca3a2c6b9f300ddf4',
urlTemplate: 'https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png',
subdomains: ['a', 'b', 'c'],
keepBuffer: 20),
new MarkerLayerOptions(
markers: [
Marker(
point: LatLng(_position.latitude, _position.longitude),
height: 200,
width: 200,
builder: (context) => IconButton(
icon: Icon(Icons.location_on),
color: Colors.red,
iconSize: 60,
onPressed: () {
print('icon tapped');
},
),
),
],
),
],
);
}
void startTracking() {
LocationOptions locationOptions =
LocationOptions(accuracy: LocationAccuracy.high, distanceFilter: 0);
StreamSubscription positionStream = _geolocator
.getPositionStream(locationOptions)
.listen((Position position) {
setState(() {
_position = position;
if (_position != null) {
// _controller.move(LatLng(_position.latitude, _position.longitude), 16);
setMap();
}
});
print(
_position.latitude.toString() + ',' + _position.longitude.toString());
});
}
void updateLocation() async {
try {
Position newPosition = await _geolocator
.getCurrentPosition(
desiredAccuracy: LocationAccuracy.bestForNavigation,
)
.timeout(new Duration(seconds: 5));
print(
'updateLocation(): ${newPosition.latitude.toString() + ',' + newPosition.longitude.toString()}');
setState(() {
_position = newPosition;
setMap();
});
} catch (error) {
print('Error updating location: ${error.toString()}');
}
}
void postRequest() async {
print('postRequest called');
// working properly
// final request =
// 'http://router.project-osrm.org/trip/v1/driving/44.5018645003438,11.340018709036542;44.501342559233315,11.336182647230146?exclude=motorway';
// final request = 'http://router.project-osrm.org/trip/v1/driving/44.5018645003438,11.340018709036542;44.501342559233315,11.33618264723014?source=first&destination=last&roundtrip=false&exclude=motorway&generate_hints=false&geometries=geojson&overview=full';
// final request =
// 'http://www.yournavigation.org/api/1.0/gosmore.php?format=geojson&v=bicycle&fast=0&layer=mapnik&flat=44.5018645003438&flon=11.340018709036542&tlat=44.501342559233315&tlon=11.336182647230146&geometry=1&instructions=1&lang=it';
// GOOOD
final request =
'http://www.yournavigation.org/api/1.0/gosmore.php?format=geojson&v=bicycle&fast=0&layer=mapnik&flat=44.5018645003438&flon=11.340018709036542&tlat=44.502138&tlon=11.340402&geometry=1&instructions=1&lang=it';
// only driving
// final request =
// 'http://www.yournavigation.org/api/1.0/gosmore.php?format=geojson&flat=52.215676&flon=5.963946&tlat=52.2573&tlon=6.1799&v=motorcar&fast=1&layer=mapnik';
// final request =
// 'https://routing.openstreetmap.de/routed-foot/route/v1/driving/13.7807085453224,51.0536161;13.7835429,51.0515885?overview=false&geometries=polyline&steps=true';
// Await the http get response, then decode the json-formatted response.
var response = await get(request);
if (response.statusCode == 200) {
var jsonResponse = convert.jsonDecode(response.body);
print('${jsonResponse.runtimeType} : $jsonResponse');
List<dynamic> coordinates = jsonResponse['coordinates'];
print('coordinates are : $coordinates');
print('coordinates are: ${coordinates.length}');
Map<String, dynamic> properties = jsonResponse['properties'];
// print('properties are $properties');
String distance = properties['distance'];
print('Route is $distance Km long.');
String instructions = properties['description'];
print('instructions are $instructions');
List<LatLng> suggestedRoute = [];
for (int i = 0; i < (coordinates.length); i++) {
dynamic coordinate = coordinates[i];
LatLng position = LatLng(coordinate[1], coordinate[0]);
suggestedRoute.add(position);
print('position is $position');
print(i);
}
print('suggestedRoute is $suggestedRoute');
} else {
print('Request failed with status: ${response.statusCode}.');
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
backgroundColor: Colors.transparent,
elevation: 0,
title: Text(
'Home',
style: TextStyle(color: Colors.orangeAccent, fontSize: 40),
),
actions: <Widget>[
IconButton(
icon: Icon(
Icons.exit_to_app,
color: Colors.orange,
size: 35,
),
onPressed: () {
BlocProvider.of<AuthenticationBloc>(context).add(
LoggedOut(),
);
},
),
],
),
backgroundColor: Colors.white,
body: SafeArea(
minimum: EdgeInsets.symmetric(horizontal: 20),
child: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Container(
height: 670,
width: 370,
child: _flutterMap,
),
SizedBox(
height: 10,
),
RaisedButton(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(5)),
onPressed: () {
startTracking();
// setState(() {
//// updateLocation();
// });
//
},
color: Colors.red,
child: Padding(
padding: EdgeInsets.all(8.0),
child: Text(
'alert',
style: TextStyle(color: Colors.white, fontSize: 30),
),
),
),
],
),
),
),
);
}
}
答案 0 :(得分：1)
有GoogleMapController个带有moveCamera / animateCamera方法。他们接受CameraUpdate参数和CameraPosition作为新目标。
class LocationLabPage extends StatefulWidget {
@override
_LocationLabPageState createState() => _LocationLabPageState();
}
class _LocationLabPageState extends State<LocationLabPage> {
GoogleMapController _mapController;
StreamSubscription _streamSubscription;
@override
void initState() {
_streamSubscription = LocationService().locationStream.listen((event) {
_mapController.moveCamera(CameraUpdate.newLatLng(LatLng(event.latitude, event.longitude)));
});
super.initState();
}
@override
void dispose() {
_streamSubscription.cancel();
super.dispose();
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(),
body: GoogleMap(
myLocationEnabled: true,
myLocationButtonEnabled: true,
initialCameraPosition: CameraPosition(target: LatLng(37.7, -122.2), zoom: 9.0),
onMapCreated: (GoogleMapController controller) {
_mapController = controller;
},
),
);
}
}
答案 1 :(得分：0)
我发现了错误。
_controller是在setMap()内部初始化的，而不是在initState()内部初始化的，所以当我在_controller.move(LatLng(_position.latitude, _position.longitude), 16);内部调用startTracking()时，抛出了与地图没有连接的错误。并没有移动地图。
将其初始化在initState()中可以正常工作。
非常感谢