Display Cursor Street Name

This example demonstrates how to create a Flutter app that displays the name of the street at the cursor position using GemKit.

When the user taps on the map, the app retrieves and displays the street name at that location.

Setup

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

Prerequisites

Make sure you completed the Environment Setup - Flutter Examples guide before starting this guide.

Build and Run

Navigate to the project folder for this example to build and run the application.

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

Run: flutter pub get

Configure the native parts:

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:

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    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:

Replace example_pathname with the actual project pathname

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android {
    defaultConfig {
        applicationId "com.magiclane.gem_kit.examples.example_pathname"
        minSdk 21
        targetSdk flutter.targetSdk
        versionCode flutterVersionCode.toInteger()
        versionName flutterVersionName
    }
    buildTypes {
        release {
            minifyEnabled false
            shrinkResources false

            // TODO: Add your own signing config for the release build.
            // Signing with the debug keys for now, so `flutter run --release` works.
            signingConfig signingConfigs.debug
        }
    }
}

iOS

In the ios/Podfile configuration file, at the top, set the minimum ios platform version to 14 like this:

platform :ios, '14.0'

We recommend you to run these commands after you copy the gem_kit into your project: |flutter clean |flutter pub get |and |cd ios |pod install

Then run the project:

flutter run --debug

or

flutter run --release

App entry and initialization

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

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

This code initializes the projectApiToken with the required authorization token and launches the app.

How It Works

1. Main App Setup: Initializes the GemKit SDK and sets up the app’s home screen with a map.

2. Displaying Street Names: The map detects touch input, centers on the selected coordinates, and displays the street name at the tapped location in a bottom-centered container.

Main Screen with Map and Street Name Display

User Interface: The map screen includes an AppBar and displays a container at the bottom showing the street name upon tapping a location on the map.

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

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

class _MyHomePageState extends State<MyHomePage> {
  late GemMapController _mapController;
  String _currentStreetName = "";

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.deepPurple[900],
        title: const Text(
          'Display Cursor Street Name',
          style: TextStyle(color: Colors.white),
        ),
      ),
      body: Stack(alignment: AlignmentDirectional.bottomCenter, children: [
        GemMap(onMapCreated: _onMapCreated, appAuthorization: projectApiToken),
        if (_currentStreetName != "")
          Padding(
            padding: const EdgeInsets.symmetric(vertical: 25.0),
            child: Container(
              color: Colors.white,
              child: Padding(
                padding: const EdgeInsets.all(8.0),
                child: Text(_currentStreetName),
              ),
            ),
          ),
      ]),
    );
  }

The container at the bottom displays the street name when it is available.

Handling Cursor Position and Retrieving Street Name

This code sets the cursor to follow the tapped location and retrieves the street name.

void _onMapCreated(GemMapController controller) async {
  _mapController = controller;

  _mapController.centerOnCoordinates(
      Coordinates(latitude: 45.472358, longitude: 9.184945));

  _mapController.preferences.enableCursor = true;
  _mapController.preferences.enableCursorRender = true;

  _mapController.registerTouchCallback((point) {
    _mapController.setCursorScreenPosition(point);
    final streets = _mapController.cursorSelectionStreets();
    setState(() {
      _currentStreetName = streets.isEmpty ? "Unnamed street" : streets.first.name;
    });
  });
}

This code initializes the map, sets the cursor to follow the user’s taps, and retrieves the street name, which is then displayed in the UI.

Flutter Examples

Maps SDK for Flutter Examples can be downloaded or cloned with Git