# Calculate Route
Last updated:
October 18, 2026
\| 5 minutes read
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[](#how-it-works "Direct link to 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[](#ui-and-map-integration "Direct link to 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[View on Github](https://github.com/magiclane/magiclane-maps-sdk-examples-for-flutter/tree/main/calculate_route/lib/main.dart?ref_type=heads#L10)
```dart
const projectApiToken = String.fromEnvironment('YOUR_API_TOKEN_HERE');
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 createState() => _MyHomePageState();
}
class _MyHomePageState extends State {
late GemMapController _mapController;
// We use the handler to cancel the route calculation.
TaskHandler? _routingHandler;
List? _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[](#route-calculation-and-map-interaction "Direct link to 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[View on Github](https://github.com/magiclane/magiclane-maps-sdk-examples-for-flutter/tree/main/calculate_route/lib/main.dart?ref_type=heads#L88)
```dart
Future _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[](#route-selection "Direct link to 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[View on Github](https://github.com/magiclane/magiclane-maps-sdk-examples-for-flutter/tree/main/calculate_route/lib/main.dart?ref_type=heads#L173)
```dart
Future _registerRouteTapCallback() async {
// Register the generic map touch gesture.
_mapController.registerOnTouch((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[](#displaying-route-information "Direct link to Displaying Route Information")
main.dart[View on Github](https://github.com/magiclane/magiclane-maps-sdk-examples-for-flutter/tree/main/calculate_route/lib/main.dart?ref_type=heads#L195)
```dart
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;
}
```