Calculate Route

In this guide you will learn how to compute a route between a departure point and a destination point, and render it on an interactive map.

Setup

First, get an API key token, see the Getting Started guide.

Prerequisites

It is required that you complete the Environment Setup - Flutter Examples guide before starting this guide.

Run the example

Start a terminal/command prompt and go to the calculate_route directory, within the flutter examples directory

Build and run the example:

Build and run

Note - the gem_kit directory containing the Maps SDK for Flutter should be in the plugins directory of the example, e.g. calculate_route/plugins/gem_kit - see the environment setup guide above.

Download project dependencies:

flutter upgrade

run the following terminal commands in the project directory, where the pubspec.yaml file is located:

flutter clean

flutter pub get

Run the example:

Web browser

flutter run

If such a question appears, select the chrome browser; in the above example, press 2.

Android

First, verify that the ANDROID_SDK_ROOT environment variable is set to the root path of your android SDK.

In android/build.gradle add the maven {} block as shown, within the allprojects {} block, for both debug and release builds, without the line numbers, those are for reference:

allprojects {
    repositories {
        google()
        mavenCentral()
        maven {
           url "${rootDir}/../plugins/gem_kit/android/build"
        }
    }
}

in android/app/build.gradle within the android {} block, in the defaultConfig {} block, the android SDK version minSdk must be set as shown below.

Additionally, for release builds, in android/app/build.gradle, within the android {} block, add the buildTypes {} block as shown:

android {
    defaultConfig {
        applicationId "com.magiclane.gem_kit.examples.calculate_route"
        minSdk 21
        targetSdk flutter.targetSdk
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
    }
    buildTypes {
        release {
            // TODO: Add your own signing config for the release build.
            // Signing with the debug keys for now, so `flutter run --release` works.
            minifyEnabled false
            shrinkResources false
            signingConfig signingConfigs.debug
        }
    }
}

Then build the apk:

flutter build apk --debug

or

flutter build apk --release

the apk file is located in the build/app/outputs/apk/debug or build/app/outputs/apk/release subdirectory, for debug or release build respectively, within the current project directory, which is calculate_route in this case.

The apk file name is app-release.apk or app-debug.apk

You can copy the apk to an android device using adb, for example:

adb push app-release.apk sdcard

And then click on the apk in the file browser on the device to install and run it.

iOS

In the ios/Podfile configuration text file, at the top, set the minimum ios platform to 13 like this:

platform :ios, '13.0'

Run pod install in the [ios folder] ./ios/

Then go back to the repository root folder and type flutter build ios to build a Runner.app.

Type flutter run to build and run on an attached device.

You can open the <path/to>/ios/Runner.xcworkspace project in Xcode and execute and debug from there.

How it works

In the calculate_route project directory, there is a text file named pubspec.yaml which contains project configuration and dependencies. The most important lines from this file are shown here:

name: calculate_route
version: 1.0.0+1

environment:
  sdk: '>=2.19.6 <3.0.0'

dependencies:
  flutter:
    sdk: flutter
  gem_kit:
    path: plugins/gem_kit

# The following section is specific to Flutter packages.
flutter:
  uses-material-design: true

The project must have a name and version. The dependencies list the Flutter SDK, and the gem_kit, Maps for Flutter SDK.

The source code is in calculate_route/lib/main.dart

import 'package:gem_kit/gem_kit_basic.dart';
import 'package:gem_kit/gem_kit_map_controller.dart';
import 'package:gem_kit/api/gem_coordinates.dart';
import 'package:gem_kit/api/gem_landmark.dart';
import 'package:gem_kit/api/gem_routingpreferences.dart';
import 'package:gem_kit/api/gem_sdksettings.dart';
import 'package:gem_kit/api/gem_types.dart';
import 'package:gem_kit/api/gem_routingservice.dart' as gem;
import 'package:gem_kit/widget/gem_kit_map.dart';
import 'package:flutter/material.dart';

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

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

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      title: 'Build route example',
      home: MyHomePage(),
    );
  }
}

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

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

The dart material package is imported, as well as the gem_kit packages for the map controller, which enables user input such as pan and zoom, the map package which draws the map, the routingservice which computes a route, the landmark and coordinates packages for geolocation, and the settings package.

The map is in a widget which is the root of the application.

class _MyHomePageState extends State<MyHomePage> {
  late GemMapController mapController;
  late SdkSettings _sdkSettings;
  late gem.RoutingService _routingService;
  List<Coordinates> waypoints = [];
  List<gem.Route> shownRoutes = [];
  bool haveRoutes = false;

  @override
  void initState() {
    super.initState();
    waypoints.add(
     Coordinates(latitude: 48.85682120481962, longitude: 2.343751354197309));
    waypoints.add(Coordinates(
     latitude: 50.846442672966944, longitude: 4.345870353765759));
  }

  Future<void> onMapCreated(GemMapController controller) async {
    mapController = controller;
    SdkSettings.create(mapController.mapId).then((value)
    {
        _sdkSettings = value;
        _sdkSettings.setAppAuthorization("YOUR_API_KEY_TOKEN");
    });
    _routingService = await gem.RoutingService.create(_mapController.mapId);
  }

The map is initialized with the map controller and the settings.

Setting the API key

The string "YOUR_API_KEY_TOKEN" should be replaced with your actual API key token string.

The waypoints for the departure and destination positions are hardcoded in the void initState() function shown above.

A tap on the purple button at the top right causes a set of routes to be computed and rendered on the map.

// Custom method for calling calculate route and creating
_onPressed(List<Coordinates> waypoints, BuildContext context) async {
// Create a landmark list
final landmarkWaypoints =
await gem.LandmarkList.create(_mapController.mapId);

// Create landmarks from coordinates and add them to the list
for (final wp in waypoints) {
  var landmark = await Landmark.create(_mapController.mapId);
  await landmark.setCoordinates(
    Coordinates(latitude: wp.latitude, longitude: wp.longitude));
  landmarkWaypoints.push_back(landmark);
}

final routePreferences = RoutePreferences();

var result = await _routingService.calculateRoute(
  landmarkWaypoints, routePreferences, (err, routes) async {
  if (err != GemError.success || routes == null) {
    return;
  } else {
    // Get the controller's preferences
    final mapViewPreferences = await _mapController.preferences();
    // Get the routes from the preferences
    final routesMap = await mapViewPreferences.routes();
    //Get the number of routes
    final routesSize = await routes.size();

    for (int i = 0; i < routesSize; i++) {
      final route = await routes.at(i);
      shownRoutes.add(route);

      final timeDistance = await route.getTimeDistance();

      final totalDistance = convertDistance(
        timeDistance.unrestrictedDistanceM +
          timeDistance.restrictedDistanceM);

      final totalTime = convertDuration(
        timeDistance.unrestrictedTimeS + timeDistance.restrictedTimeS);
      // Add labels to the routes
      await routesMap.add(route, i == 0,
        label: '$totalDistance \n $totalTime');
     }
     // Select the first route as the main one
     final mainRoute = await routes.at(0);
     final width = MediaQuery.of(context).size.width - 150;
     final height = MediaQuery.of(context).size.height - 150;
     await _mapController.centerOnRoute(mainRoute,
         rc: RectType(
             x: 50, y: 50, width: width.toInt(), height: height.toInt()));
   }
 });
 haveRoutes = true;
 setState(() {});
 return result;
}

This is the custom method to compute a route by calling: _routingService.calculateRoute(), rendering the resulting set of routes on the map, then choosing the route at index 0 (the first one), setting it as the mainRoute and then centering the main route so it fits in the viewport: _mapController.centerOnRoute()

_removeRoutes(List<gem.Route> routes) async {
  final prefs = await _mapController.preferences();
  final routesMap = await prefs.routes();

  for (final route in routes) {
    routesMap.remove(route);
  }
  haveRoutes = false;
  setState(() {});
}

Function to remove the computed routes rendered on the map.

@override
Widget build(BuildContext context) {
  return Scaffold(
    body: Center(
      child: GemMap(
        onMapCreated: onMapCreated,
      ),
    ),
    floatingActionButtonLocation: FloatingActionButtonLocation.endTop,
    floatingActionButton: haveRoutes
       ? FloatingActionButton(
           backgroundColor: Colors.red,
           onPressed: () => _removeRoutes(shownRoutes),
           child: const Icon(Icons.cancel),
         )
       : FloatingActionButton(
           backgroundColor: Colors.deepPurple[900],
           onPressed: () => _onPressed(waypoints, context),
           child: const Icon(Icons.directions),
         ),
    resizeToAvoidBottomInset: false,
  );
}

Button for calling the _removeRoutes function.

A tap on the red button at the top right causes the rendered set of routes to be removed from the map.

String convertDistance(int meters) {
  if (meters >= 1000) {
    double kilometers = meters / 1000;
    return '${kilometers.toStringAsFixed(1)} km';
  } else {
    return '${meters.toString()} m';
  }
}

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;
}
}

Automatic conversion of distance to meters or kilometers, respectively, depending on length, and automatic conversion of time in hours and minutes.