I’m using the new dart version <2.18.1> with null safety enabled.
And I’m using the android studio to code this.
This is maps_screen.dart
`
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter_typeahead/flutter_typeahead.dart';
import 'package:geolocator/geolocator.dart';
import 'package:gmapsdemo/places_api.dart';
import 'package:google_maps_flutter/google_maps_flutter.dart';
class MapsScreen extends StatefulWidget {
MapsScreen({Key? key}) : super(key : key);
@override
_MapsScreenState createState() => _MapsScreenState();
}
class _MapsScreenState extends State<MapsScreen> {
final Completer<GoogleMapController> _controller = Completer();
static const LatLng _initialPosition = LatLng(6.8747747, 79.8645194);
final Set<Marker> _markers = {};
late LatLng user_current_position;
MapType currentMapType = MapType.normal;
TextEditingController _addressController = TextEditingController();
void _onMapCreate(GoogleMapController controller)
{
_controller.complete(controller);
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text('Map Screen'),
),
body: Stack(
children: [
Container(
child: GoogleMap(
onMapCreated: _onMapCreate,
initialCameraPosition:
CameraPosition(target: _initialPosition, zoom: 9),
markers: _markers,
onTap: (latLng){
_onAddMaker(latLng);
},
mapType: currentMapType,
),
),
Positioned(
child: Container(
margin: EdgeInsets.only(top: 10, left: 10, right: 10),
height: 50,
decoration: BoxDecoration(
color: Colors.white,
borderRadius: BorderRadius.circular(8),
boxShadow: [
BoxShadow(
color: Colors.black.withOpacity(0.2),
spreadRadius: 3,
blurRadius: 2,)
]),
child: TypeAheadField<Suggestion>(
textFieldConfiguration: TextFieldConfiguration(
controller: _addressController,
decoration: InputDecoration(
alignLabelWithHint: true,
hintText: 'Type Address',
border: InputBorder.none,
hintStyle: TextStyle(fontSize: 20),
isCollapsed: true),
),
hideOnEmpty: true,
hideOnLoading: true,
suggestionsCallback: (pattern) async {
return //await PlacesAPIProvider('23456')
.fetchSuggestions(pattern);//
},
itemBuilder: (context, suggestion) {
return GestureDetector(
onTap: (){},
child: ListTile(
title: Text(suggestion.description,
style: TextStyle(color: Colors.black)),
),
);
},
onSuggestionSelected: (selectedSuggestion) {},
),
),
),
Positioned(
bottom: 8,
left: 8,
child: FloatingActionButton(
child: Icon(
Icons.my_location,
color: Colors.white,
),
onPressed: () async{
await getUserCurrentPosition().then((value) async{
await _navigateCameraToPosition(value);
});
},
)),
Positioned(
bottom: 8,
left: 80,
child: FloatingActionButton(
child: Icon(
Icons.map,
color: Colors.white,
),
onPressed: (){
setState(() {
currentMapType = (currentMapType == MapType) ?
MapType.satellite : MapType.normal;
});
},
))
],
),
);
}
void _onAddMaker(LatLng position)
{
setState(() {
_markers.add(
Marker(
icon: BitmapDescriptor.defaultMarker,
markerId: MarkerId(position.longitude.toString()),
position: position,
infoWindow: InfoWindow(
title: "Maker",
snippet: position.toString())
)
);
});
}
Future<LatLng> getUserCurrentPosition() async
{
var position = await Geolocator.getCurrentPosition(
desiredAccuracy: LocationAccuracy.best
);
setState(() {
user_current_position = LatLng(position.latitude, position.longitude);
});
return user_current_position;
}
Future _navigateCameraToPosition(LatLng position) async
{
final controller = await _controller.future;
await controller.animateCamera(CameraUpdate.newCameraPosition(
CameraPosition(target: position , zoom: 12)
));
}
}
`
This is places_api.dart
import 'dart:convert';
import 'package:http/http.dart' as http;
class PlacesAPIProvider{
final sessionToken;
PlacesAPIProvider(this.sessionToken);
final apiKey = 'AIzaSyCSmS579erjjuZFo3WB8vSL_d5T6nGzFA0';
Future<Object> fetchSuggestions(String query)
async {
if( query.isNotEmpty){
final request = 'https://maps.googleapis.com/maps/api/place/autocomplete/json'
'input=$query&types=address&language=en&components=cpuntry:sl'
'&key=$apiKey&sessointoken=$sessionToken';
final response = await http.get(Uri.parse(request));
if(response.statusCode == 200)
{
final result = json.decode(response.body);
if (result['status'] == 'ok')
{
return result['predications']
.map<Suggestion>(
(p) => Suggestion( p['place_id'], p['description']))
.toList();
}else{
return [];
}
}
else{
return [];
}
}
else{
return [];
}
return '';
}
}
class Suggestion{
final String placeId;
final String description;
Suggestion( this.placeId , this.description);
}
I’m getting this error
The return type 'Object' isn't a 'Future<Iterable<Suggestion>>', as required by the closure's context.
This is where the error is. i put // where the red underline is.
hideOnEmpty: true,
hideOnLoading: true,
suggestionsCallback: (pattern) async {
return //await PlacesAPIProvider('23456')
.fetchSuggestions(pattern);//
},
and this error in the Run log:
lib/maps_screen.dart:84:26: Error: A value of type 'Object' can't be returned from an async function with return type 'Future<Iterable<Suggestion>>'.
- 'Object' is from 'dart:core'.
- 'Future' is from 'dart:async'.
- 'Iterable' is from 'dart:core'.
- 'Suggestion' is from 'package:gmapsdemo/places_api.dart' ('lib/places_api.dart').
return await PlacesAPIProvider('23456')
^
FAILURE: Build failed with an exception.
* Where:
Script 'C:\Users\induw\Documents\flutter\Flutter\flutter_windows_3.3.2-stable\flutter\packages\flutter_tools\gradle\flutter.gradle' line: 1159
* What went wrong:
Execution failed for task ':app:compileFlutterBuildDebug'.
> Process 'command 'C:\Users\induw\Documents\flutter\Flutter\flutter_windows_3.3.2-stable\flutter\bin\flutter.bat'' finished with non-zero exit value 1
* Try:
> Run with --stacktrace option to get the stack trace.
> Run with --info or --debug option to get more log output.
> Run with --scan to get full insights.
* Get more help at https://help.gradle.org
BUILD FAILED in 1m 42s
Exception: Gradle task assembleDebug failed with exit code 1
Please help me I’m a beginner.
I tried google but I couldn’t find a similar error.
>Solution :
The return type of fetchSuggestions is List<Suggestion> and not Object.
So, change this line.
/// replace Object with Future<Iterable<Suggestion>>
Future<Future<Iterable<Suggestion>>> fetchSuggestions(String query) async{}
More optimal way:
Future<Future<List<Suggestion>>> fetchSuggestions(String query) async{}