PilotVault/Fly Agent App/lib/pilot_location.dart

import 'dart:async';

import 'package:flutter/foundation.dart';
import 'package:geolocator/geolocator.dart';

/// The phone's own GPS fix: where the pilot stands. Used for the briefing
/// weather, the distance to the aircraft, and as the pilot position on the
/// live uplink (the Web App also falls back on it when the drone has no fix).
class PilotLocation extends ChangeNotifier {
  Position? position;
  String? problem;
  StreamSubscription<Position>? _sub;

  Future<void> start() async {
    if (_sub != null) return;
    try {
      if (!await Geolocator.isLocationServiceEnabled()) {
        problem = 'Location is off';
        notifyListeners();
        return;
      }
      LocationPermission p = await Geolocator.checkPermission();
      if (p == LocationPermission.denied) p = await Geolocator.requestPermission();
      if (p == LocationPermission.denied || p == LocationPermission.deniedForever) {
        problem = 'Location permission refused';
        notifyListeners();
        return;
      }
      problem = null;
      _sub = Geolocator.getPositionStream(
        locationSettings: const LocationSettings(accuracy: LocationAccuracy.high, distanceFilter: 2),
      ).listen((Position pos) {
        position = pos;
        notifyListeners();
      }, onError: (Object e) {
        problem = e.toString();
        notifyListeners();
      });
    } catch (e) {
      problem = e.toString();
      notifyListeners();
    }
  }

  @override
  void dispose() {
    _sub?.cancel();
    super.dispose();
  }
}