Assets Map Styles

_{Estimated reading time: 3 minutes}

This example showcases how to build a Flutter app featuring an interactive map with a custom style, seamlessly imported from the assets folder, using the Maps SDK for Flutter.

How it works

The example app demonstrates the following features:

• Main App Setup : Initializes GemKit and displays a map view with an AppBar.
• Map Styling : The user taps an icon to apply a style, loaded from a file in the app assets folder.
• Loading Feedback : Displays a loading message until the style is fully applied.

Map styles loading	Applied map style

Add style to project

In the root directory of your project, create a new folder named assets. Specify the path to the assets folder in the pubspec.yaml file. Modify the file as follows:

  flutter:
uses-material-design: true

assets:
  - assets/

Place a .style file inside the assets directory.

UI and Map Integration

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

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

class _MyHomePageState extends State<MyHomePage> {
  late GemMapController _mapController;
  bool _isStyleLoaded = false;

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Colors.deepPurple[900],
        title: const Text('Assets Map Style', style: TextStyle(color: Colors.white)),
        actions: [
          if (!_isStyleLoaded)
            IconButton(
              onPressed: _applyStyle,
              icon: Icon(Icons.map, color: Colors.white),
            ),
        ],
      ),
      body: GemMap(
        key: ValueKey("GemMap"),
        onMapCreated: _onMapCreated,
        appAuthorization: projectApiToken,
      ),
    );
  }

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

This code sets up the main screen with a map and a button that triggers the _applyStyle method to load a custom style file.

Loading and Applying Map Styles

This code loads the .style file as bytes, applies it to the map with a smooth transition, and centers the map on specified coordinates.

Future<void> _applyStyle() async {
  _showSnackBar(context, message: "The map style is loading.");

  await Future<void>.delayed(Duration(milliseconds: 250));
  final styleData = await _loadStyle();

  _mapController.preferences.setMapStyleByBuffer(styleData, smoothTransition: true);

  setState(() {
    _isStyleLoaded = true;
  });

  if (mounted) {
    ScaffoldMessenger.of(context).hideCurrentSnackBar();
  }
  _mapController.centerOnCoordinates(Coordinates(latitude: 45, longitude: 20), zoomLevel: 25);
}

Loading the Style File

This method reads the .style file from assets and returns the data as Uint8List bytes.

Future<Uint8List> _loadStyle() async {
  final data = await rootBundle.load('assets/Basic_1_Oldtime-1_21_656.style');
  return data.buffer.asUint8List();
}

Flutter Examples

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