Calculate Route

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This example demonstrates how to create a Flutter app that calculates a route between two locations and displays it on a map using Maps SDK for Flutter.

How It Works

The example app demonstrates the following features:

• Calculate a route between two landmarks.
• Display the route on a map and allow user interaction with the route.
• Provide options to cancel route calculation or clear the routes from the map.

Initial map view

Route presented

UI and Map Integration

This code sets up the basic structure of the app, including the map and the app bar. It also provides buttons in the app bar for building, canceling, and clearing routes.

main.dart

const projectApiToken = String.fromEnvironment('GEM_TOKEN');

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

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(debugShowCheckedModeBanner: false, title: 'Calculate Route', home: MyHomePage());
  }
}

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

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  late GemMapController _mapController;

  // We use the handler to cancel the route calculation.
  TaskHandler? _routingHandler;

  List<Route>? _routes;

  @override
  void dispose() {
    GemKit.release();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.deepPurple[900],
        title: const Text('Calculate Route', style: TextStyle(color: Colors.white)),
        actions: [
          // Routes are not built.
          if (_routingHandler == null && _routes == null)
            IconButton(
              onPressed: () => _onBuildRouteButtonPressed(context),
              icon: const Icon(Icons.route, color: Colors.white),
            ),
          // Routes calculating is in progress.
          if (_routingHandler != null)
            IconButton(
              onPressed: () => _onCancelRouteButtonPressed(),
              icon: const Icon(Icons.stop, color: Colors.white),
            ),
          // Routes calculating is finished.
          if (_routes != null)
            IconButton(
              onPressed: () => _onClearRoutesButtonPressed(),
              icon: const Icon(Icons.clear, color: Colors.white),
            ),
        ],
      ),
      body: GemMap(key: ValueKey("GemMap"), onMapCreated: _onMapCreated, appAuthorization: projectApiToken),
    );
  }

Route Calculation and Map Interaction

This code handles the calculation of routes between two landmarks, displays the routes on the map, and provides options to cancel or clear the routes. The map is centered on the calculated routes, and a label showing the distance and duration is displayed.

main.dart

  // The callback for when map is ready to use.
  Future<void> _onMapCreated(GemMapController controller) async {
    // Save controller for further usage.
    _mapController = controller;

    // Register route tap gesture callback.
    await _registerRouteTapCallback();
  }

  void _onBuildRouteButtonPressed(BuildContext context) {
    // Define the departure.
    final departureLandmark = Landmark.withLatLng(latitude: 48.85682, longitude: 2.34375);

    // Define the destination.
    final destinationLandmark = Landmark.withLatLng(latitude: 50.84644, longitude: 4.34587);

    // Define the route preferences.
    final routePreferences = RoutePreferences();

    _showSnackBar(context, message: "The route is being calculated.");

    // Calling the calculateRoute SDK method.
    // (err, results) - is a callback function that gets called when the route computing is finished.
    // err is an error enum, results is a list of routes.

    _routingHandler = RoutingService.calculateRoute([departureLandmark, destinationLandmark], routePreferences, (
      err,
      routes,
    ) {
      // If the route calculation is finished, we don't have a progress listener anymore.
      _routingHandler = null;
      ScaffoldMessenger.of(context).clearSnackBars();

      // If there aren't any errors, we display the routes.
      if (err == GemError.success) {
        // Get the routes collection from map preferences.
        final routesMap = _mapController.preferences.routes;

        // Display the routes on map.
        for (final route in routes) {
          routesMap.add(route, route == routes.first, label: getMapLabel(route));
        }

        // Center the camera on routes.
        _mapController.centerOnRoutes(routes: routes);
        setState(() {
          _routes = routes;
        });
      }
    });

    setState(() {});
  }

  void _onClearRoutesButtonPressed() {
    // Remove the routes from map.
    _mapController.preferences.routes.clear();

    setState(() {
      _routes = null;
    });
  }

  void _onCancelRouteButtonPressed() {
    // If we have a progress listener we cancel the route calculation.
    if (_routingHandler != null) {
      RoutingService.cancelRoute(_routingHandler!);

      setState(() {
        _routingHandler = null;
      });
    }
  }

Route Selection

This code enables the user to select a specific route on the map by tapping on it. The selected route becomes the main route displayed.

main.dart

// In order to be able to select an alternative route, we have to register the route tap gesture callback.
Future<void> _registerRouteTapCallback() async {
  // Register the generic map touch gesture.
  _mapController.registerTouchCallback((pos) async {
    // Select the map objects at gives position.
    await _mapController.setCursorScreenPosition(pos);

    // Get the selected routes.
    final routes = _mapController.cursorSelectionRoutes();

    // If there is  a route at position, we select it as the main one on the map.
    if (routes.isNotEmpty) {
      _mapController.preferences.routes.mainRoute = routes[0];
    }
  });
}

Displaying Route Information

main.dart

  // Show a snackbar indicating that the route calculation is in progress.
  void _showSnackBar(BuildContext context, {required String message, Duration duration = const Duration(hours: 1)}) {
    final snackBar = SnackBar(content: Text(message), duration: duration);

    ScaffoldMessenger.of(context).showSnackBar(snackBar);
  }
}

String getMapLabel(Route route) {
  return '${convertDistance(route.getTimeDistance().totalDistanceM)} \n${convertDuration(route.getTimeDistance().totalTimeS)}';
}

// Utility function to convert the meters distance into a suitable format.
String convertDistance(int meters) {
  if (meters >= 1000) {
    double kilometers = meters / 1000;
    return '${kilometers.toStringAsFixed(1)} km';
  } else {
    return '${meters.toString()} m';
  }
}

// Utility function to convert the seconds duration into a suitable format.
String convertDuration(int seconds) {
  int hours = seconds ~/ 3600; // Number of whole hours
  int minutes = (seconds % 3600) ~/ 60; // Number of whole minutes

  String hoursText = (hours > 0) ? '$hours h ' : ''; // Hours text
  String minutesText = '$minutes min'; // Minutes text

  return hoursText + minutesText;
}