raw_gnss_2025 2.0.1

Get Raw GNSS Data Points for Android on Flutter - Originated code from raw_gnss by Deven Joshi

example/lib/main.dart

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:geolocator/geolocator.dart';
import 'package:permission_handler/permission_handler.dart';
import 'package:raw_gnss_2025/gnss_measurement_model.dart';
import 'package:raw_gnss_2025/gnss_status_model.dart';
import 'package:raw_gnss_2025/raw_gnss.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: Scaffold(
        appBar: AppBar(
          title: const Text("Demo"),
        ),
        body: const HomeScreen(),
      ),
    );
  }
}

class HomeScreen extends StatefulWidget {
  const HomeScreen({super.key});

  @override
  _HomeScreenState createState() => _HomeScreenState();
}

class _HomeScreenState extends State<HomeScreen> {
  var _hasPermissions = false;
  late RawGnss _gnss;
  Timer? _noFixTimer;
  bool _timedOut = false;
  StreamSubscription<Position>? _posSub;
  @override
  void initState() {
    super.initState();

    _gnss = RawGnss();

    Permission.location.request().then((value) {
      final granted = value.isGranted;
      setState(() => _hasPermissions = granted);
      if (granted) {
        _startNoFixTimer();
        _kickGpsStart();
      }
    });
  }

  @override
  Widget build(BuildContext context) =>
      _hasPermissions ? _buildGNSSMessagesStream()
      // _buildGNSSMeasurementStream ()
      //_buildGNSSSnapshotStream() 
      
      
      : _loadingSpinner();

  void _startNoFixTimer() {
    _noFixTimer?.cancel();
    _noFixTimer = Timer(const Duration(seconds: 20), () {
      if (mounted) setState(() => _timedOut = true);
    });
  }

  Future<void> _kickGpsStart() async {
    final enabled = await Geolocator.isLocationServiceEnabled();
    if (!enabled) return;

    // Make a one-shot high-accuracy request to wake GNSS hardware.
    try {
      await Geolocator.getCurrentPosition(
        desiredAccuracy: LocationAccuracy.best,
        timeLimit: const Duration(seconds: 15),
      );
    } catch (_) {
      // Ignore; this is only to trigger hardware start.
    }

    // Keep a short-lived stream to sustain GNSS until first fix.
    _posSub?.cancel();
    _posSub = Geolocator.getPositionStream(
      locationSettings: const LocationSettings(
        accuracy: LocationAccuracy.best,
        distanceFilter: 0,
        timeLimit: Duration(minutes: 2),
      ),
    ).listen((_) {}, onError: (_) {});
  }

  Widget _buildGNSSSnapshotStream() {
    return StreamBuilder<GnssStatusModel>(
      stream: _gnss.gnssStatusEvents,
      builder: (context, snapshot) {
        if (!snapshot.hasData) {
          return _timedOut ? _noFixHelp() : _loadingSpinner();
        }

        final snapshotmodel = snapshot.data!;
        final count = snapshotmodel.satelliteCount ?? 0;
        final lresultJSON = snapshotmodel.toJson();
        debugPrint('GNSS event received: satelliteCount=$count');
        debugPrint('GNSS event received: json=$lresultJSON');

        return Column(
          children: [
            Padding(
              padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
              child: Row(
                children: [
                  Chip(label: Text('Satellites: $count')),
                ],
              ),
            ),
            const Divider(height: 1),
            Expanded(
              child: SingleChildScrollView(
                scrollDirection: Axis.horizontal,
                child: DataTable(
                  columns: const [
                    DataColumn(label: Text('Position')),
                    DataColumn(label: Text('Data')),
                  ],
                  rows: List<DataRow>.generate(
                    count,
                    (index) => DataRow(
                      cells: [
                        DataCell(Text('$index')),
                        DataCell(Text(
                            snapshotmodel.status![index].toJson().toString())),
                      ],
                    ),
                  ),
                ),
              ),
            ),
          ],
        );
      },
    );
  }

  Widget _buildGNSSMeasurementStream() {
    return StreamBuilder<GnssMeasurementModel>(
      stream: _gnss.gnssMeasurementEvents,
      builder: (context, measurements) {
        if (!measurements.hasData) {
          return _timedOut ? _noFixHelp() : _loadingSpinner();
        }

        final measurementsmodel = measurements.data!;
        final count = measurementsmodel.contents ?? 0;
        final lresultJSON = measurementsmodel.toJson();
        debugPrint('GNSS Measurement received: satelliteCount=$count');
        debugPrint('GNSS Measurement received: json=$lresultJSON');

        return Column(
          children: [
            Padding(
              padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 8),
              child: Row(
                children: [
                  Chip(label: Text('Satellites: $count')),
                ],
              ),
            ),
            const Divider(height: 1),
            Expanded(
              child: SingleChildScrollView(
                scrollDirection: Axis.horizontal,
                child: DataTable(
                  columns: const [
                    DataColumn(label: Text('Position')),
                    DataColumn(label: Text('Data')),
                  ],
                  rows: List<DataRow>.generate(
                    count,
                    (index) => DataRow(
                      cells: [
                        DataCell(Text('$index')),
                        DataCell(Text(measurementsmodel.measurements![index]
                            .toJson()
                            .toString())),
                      ],
                    ),
                  ),
                ),
              ),
            ),
          ],
        );
      },
    );
  }

  Widget _buildGNSSMessagesStream() {
    return StreamBuilder<dynamic>(
        stream: _gnss.gnssNavigationMessageEvents,
        builder: (context, navmessages) {
          final lresultJSON = navmessages;
          debugPrint('GNSS Messages received: json=$lresultJSON');

          return Text(lresultJSON.toString());
        });
  }

  Widget _loadingSpinner() => const Center(child: CircularProgressIndicator());

  Widget _noFixHelp() => Center(
        child: Padding(
          padding: const EdgeInsets.all(16.0),
          child: Column(
            mainAxisSize: MainAxisSize.min,
            children: [
              const Text(
                'Waiting for GNSS fix...\n\n'
                'Tips:\n'
                '• Go outdoors with clear sky view\n'
                '• Ensure Location is ON and Precise\n'
                '• Keep the app in foreground',
                textAlign: TextAlign.center,
              ),
              const SizedBox(height: 16),
              ElevatedButton(
                onPressed: () {
                  openAppSettings();
                },
                child: const Text('Open App Settings'),
              ),
            ],
          ),
        ),
      );

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