Finger Route

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This example demonstrates how to create a Flutter app that allows users to draw a route on a map using their finger, calculates the route based on the drawn waypoints, and displays it using the Maps SDK for Flutter.

How It Works

The example app demonstrates the following features:

• Allow users to draw a route on the map with their finger.
• Calculate a route based on the drawn waypoints.
• Display the route on a map and provide options to cancel or clear the routes.

Initial map view

Finger-drawn route

Calculated route based on drawing

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 drawing, building, canceling, and clearing routes.

main.dart

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

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

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(debugShowCheckedModeBanner: false, title: 'Finger 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;

  bool _areRoutesBuilt = false;
  bool _isInDrawingMode = false;

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.deepPurple[900],
        title: const Text('Finger Route', style: TextStyle(color: Colors.white)),
        actions: [
          if (_routingHandler == null && _areRoutesBuilt == false && _isInDrawingMode == false)
            IconButton(
              onPressed: () => _onDrawPressed(),
              icon: const Icon(CupertinoIcons.hand_draw, color: Colors.white),
            ),
          // Routes are not built.
          if (_routingHandler == null && _areRoutesBuilt == false && _isInDrawingMode == true)
            IconButton(
              onPressed: () => _onBuildRouteButtonPressed(context),
              icon: const Icon(Icons.done, 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 (_areRoutesBuilt == true)
            IconButton(
              onPressed: () => _onClearRoutesButtonPressed(),
              icon: const Icon(Icons.clear, color: Colors.white),
            ),
        ],
      ),
      body: GemMap(key: ValueKey("GemMap"), onMapCreated: _onMapCreated, appAuthorization: projectApiToken),
    );
  }

Drawing and Route Calculation

This code handles drawing waypoints on the map, calculating the route based on those waypoints, 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.
  void _onMapCreated(GemMapController controller) {
    // Save controller for further usage.
    _mapController = controller;
  }

  void _onDrawPressed() {
    _mapController.enableDrawMarkersMode();
    setState(() {
      _isInDrawingMode = true;
    });
  }

  void _onBuildRouteButtonPressed(BuildContext context) {
    final waypoints = _mapController.disableDrawMarkersMode();

    // Define the route preferences.
    final routePreferences = RoutePreferences(accurateTrackMatch: false, ignoreRestrictionsOverTrack: true);

    _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(waypoints, routePreferences, (err, routes) {
      // If the route calculation is finished, we don't have a progress listener anymore.
      setState(() {
        _routingHandler = null;
        _isInDrawingMode = false;
      });

      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(() {
          _areRoutesBuilt = true;
        });
      }
    });

    setState(() {});
  }

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

    setState(() {
      _areRoutesBuilt = false;
    });
  }

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

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

  // 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);
  }

Displaying Route Information

main.dart

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;
}