Custom Position Icon

_{Estimated reading time: 4 minutes}

This example presents how to create an app that displays a custom icon for the position tracker on a map using Maps SDK for Flutter.

How it works

The example app demonstrates the following features:

• Display a custom icon for the position tracker on the map.
• Handle user interaction to start following the current position.

Default position tracker icon	Custom position tracker icon

Saving Assets

Before running the app, ensure that you save the necessary files (such as the custom icon or 3D object) into the assets directory. For example:

• Save your custom icon image (e.g., navArrow.png ) in the assets folder.

Update your pubspec.yaml file to include these assets:

flutter:
  assets:
    - assets/

UI and Map Integration

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

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

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

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

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

  PermissionStatus _locationPermissionStatus = PermissionStatus.denied;
  bool _hasLiveDataSource = false;

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.deepPurple[900],
        title: const Text('Custom Position Icon', style: TextStyle(color: Colors.white)),
        actions: [
          IconButton(
            onPressed: _onFollowPositionButtonPressed,
            icon: const Icon(
              Icons.location_searching_sharp,
              color: Colors.white,
            ),
          ),
        ],
      ),
      body: GemMap(
        key: ValueKey("GemMap"),
        onMapCreated: _onMapCreated,
        appAuthorization: projectApiToken,
      ),
    );
  }

This code defines the main UI elements, including the map and an app bar with a button to follow the current position.

Map Creation and Custom Position Tracker Icon

This method initializes the map controller, loads a custom icon for the position tracker from the assets, and applies it with a specified scale.

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

  // You can upload a custom icon for the position tracker, it can also be a 3D object as "quad.glb" file in the assets, or use a texture.
  // final bytes = await loadAsUint8List('assets/quad.glb');
  final bytes = await loadAsUint8List('assets/navArrow.png');
  setPositionTrackerImage(bytes, scale: 0.5);
}

Handling Position Tracking

This method handles user interaction to request location permissions, sets the live data source, and starts following the current position on the map.

void _onFollowPositionButtonPressed() async {
  if (kIsWeb) {
    // On web platform permission are handled differently than other platforms.
    // The SDK handles the request of permission for location.
    _locationPermissionStatus = PermissionStatus.granted;
  } else {
    // For Android & iOS platforms, permission_handler package is used to ask for permissions.
    _locationPermissionStatus = await Permission.locationWhenInUse.request();
  }

  if (_locationPermissionStatus == PermissionStatus.granted) {
    // After the permission was granted, we can set the live data source (in most cases the GPS).
    // The data source should be set only once, otherwise we'll get -5 error.
    if (!_hasLiveDataSource) {
      PositionService.instance.setLiveDataSource();
      _hasLiveDataSource = true;
    }

    // Optionally, we can set an animation
    final animation = GemAnimation(type: AnimationType.linear);

    // Calling the start following position SDK method.
    _mapController.startFollowingPosition(animation: animation);

    setState(() {});
  }
}

Utility Functions

The setPositionTrackerImage method is crucial as it allows you to customize the position tracker icon with any image or 3D object. Ensure the image is correctly loaded from assets and properly scaled to fit your application’s design.

// Helper function to load an asset as byte array.
Future<Uint8List> loadAsUint8List(String filename) async {
  final fileData = await rootBundle.load(filename);
  return fileData.buffer.asUint8List();
}

// Method that sets the custom icon for the position tracker.
void setPositionTrackerImage(Uint8List imageData, {double scale = 1.0}) {
  try {
    MapSceneObject.customizeDefPositionTracker(imageData, SceneObjectFileFormat.tex);
    final positionTracker = MapSceneObject.getDefPositionTracker();

    positionTracker.scale = scale;
  } catch (e) {
    throw (e.toString());
  }
}

Flutter Examples

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