Flutter 中的纬度和经度为空（获取当前位置）

Question

I am using this plugin flutter_geofence to get current location latitude and longitude. Below is the sample dart code, problem i facing is inside the Geofence body i can get latitude and longitude but when i try to access outside it is getting null.

return Scaffold(
          body: Container(
            child: GestureDetector(
                onTap: () {
                  var latitude;
                  var longitude;
                  Geofence.initialize();
                  Geofence.requestPermissions();
                  Geofence.getCurrentLocation().then((cd) {
                    latitude = cd!.latitude;
                    longitude = cd.longitude;
                  });
                  print(latitude); // getting null
                  print(longitude); // getting null
                },
                child: Center(child: Text('Test'))),
          ),
        );

DataService.class

class DataService {
Future<List<RecommendedForYouData>?> makeRequestRecommendedForYou(
      BuildContext context) async {
var latitude;
var longitude;
Geofence.initialize();
                  Geofence.requestPermissions();
                  Geofence.getCurrentLocation().then((cd) {
                    latitude = cd!.latitude;
                    longitude = cd.longitude;
                  });
                  print(latitude); // getting null
                  print(longitude); // getting null
}
}

Answer 1

This problem happend because your variables are outside the function (Geofence.getCurrentLocation().then ...), if you put this variables inside {} probably you can get different value than null, but I recommend create a new function outside the build method.

1. If you use a Stateful Widget:

• Declare your variables in the top of your class.
• Use initState and call your methods inside (Geofence.initialize(), Geofence.requestPermissions(), Geofence.getCurrentLocation())
• You can create a specific function outside the initState to call inside of your build method.
• Inside your specific functions you need call the setState function to rebuild your UI.

I recommend you use a state management like bloc or provider instead of setState.