Chained async methods don't show result in Widget with FutureBuilder - flutter

Question

I am having a problem displaying asynchronous data in a text widget.
I'm doing two chained asynchronous methods to search for the coordinates and then search for the city from the smartphone:
Future<String> _getCity() async {
Future<Position> pos = Geolocator().getCurrentPosition(desiredAccuracy: LocationAccuracy.low);
String city = "";
pos.then((result) {
return result;
})
.then((result) async {
List<Placemark> listPlacemark = await Geolocator().placemarkFromPosition(result);
return listPlacemark;
})
.then((result) {
return result.first;
})
.then((result) {
city = result.subAdministrativeArea;
// print( city ); -> Here it's showing correct data in console
});
return city;
}
The city appears on the console in that print command that is commented out.
To fill the text widget I'm doing this:
Padding(
padding: EdgeInsets.all(12),
child: FutureBuilder<String>(
future: _getCity(), // a Future<String> or null
builder: (BuildContext context, AsyncSnapshot<String> snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.none:
return Text('Error loading location');
case ConnectionState.waiting:
return Text('Waiting...');
default:
if (snapshot.hasError) {
return Text('Error loading location');
} else {
return Text(snapshot.data);
}
}
},
),
),
I called the _getCity method inside the initState method and it also worked.
The waiting message has already appeared but now everything is blank, what is missing?
I thank you for your attention!

Answer 1

Even if you return a value from the callback of then(), the value is not returned from _getCity(). You need to return Future.
Future<String> _getCity() async {
Future<Position> pos = Geolocator().getCurrentPosition(desiredAccuracy: LocationAccuracy.low);
return pos.then((result) {
return result;
}).then((result) async {
List<Placemark> listPlacemark = await Geolocator().placemarkFromPosition(result);
return listPlacemark;
}).then((result) {
return result.first;
}).then((result) {
return result.subAdministrativeArea;
});
}
By the way, do you need so many thens?
I've never used Geolocator(), so this is just a guess, but some of them may be removed because it looks like listPlacemark, result.first and result.subAdministrativeArea are not Future and you just want to extract a value from List<Position>. If my guess is right, the following will do.
Future<String> _getCity() async {
Future<Position> pos = Geolocator().getCurrentPosition(desiredAccuracy: LocationAccuracy.low);
return pos.then((result) async {
List<Placemark> listPlacemark = await Geolocator().placemarkFromPosition(result);
return listPlacemark.first.subAdministrativeArea;
});
}