Introduction

In this Flutter Mapbox advanced tutorial, we’ll explore two powerful features—point clustering and offline map packs—to build high-performance, resilient mobile maps. Clustering reduces marker overload when zoomed out, while offline maps ensure that tiles and vector data remain available without a network. By the end, you’ll have an advanced Flutter Mapbox implementation that handles hundreds of markers gracefully and caches map regions for offline browsing.

Setting Up Mapbox in Flutter

Before diving in, add the official Mapbox GL plugin to your pubspec.yaml:

dependencies:
  flutter:
    sdk: flutter
  mapbox_gl

Obtain a Mapbox access token at https://account.mapbox.com, then configure Android’s AndroidManifest.xml and iOS’s Info.plist as per the plugin docs. Initialize a MapboxMap widget and grab its controller via onMapCreated:.

MapboxMap(
  accessToken: MAPBOX_ACCESS_TOKEN,
  onMapCreated: _onMapCreated,
  initialCameraPosition:
      CameraPosition(target: LatLng(37.7749, -122.4194), zoom: 10),
)

Implementing Clustering

Flutter advanced Mapbox clustering leverages GeoJSON sources with cluster parameters. First, prepare a GeoJSON feature collection of your points. Then in _onMapCreated:

Future<void> _onMapCreated(MapboxMapController controller) async {
  final geojson = await rootBundle.loadString('assets/points.geojson');
  await controller.addSource(
    'clusteredPoints',
    GeojsonSourceProperties(
      data: geojson, cluster: true, clusterRadius: 50, clusterMaxZoom: 14,
    ),
  );
  // Circle layer for clusters
  await controller.addCircleLayer(
    'clusteredPoints', 'clusterCircles',
    CircleLayerProperties(
      circleColor: [
        'step', ['get', 'point_count'],
        '#51bbd6', 0, '#f1f075', 100, '#f28cb1'
      ],
      circleRadius: ['step', ['get', 'point_count'], 20, 100, 30, 750, 40],
    ),
  );
  // Symbol layer for cluster counts
  await controller.addSymbolLayer(
    'clusteredPoints', 'clusterCount',
    SymbolLayerProperties(
      textField: '{point_count_abbreviated}',
      textSize: 12,
      textColor: '#000000',
    ),
  );
  // Symbol layer for single points
  await controller.addSymbolLayer(
    'clusteredPoints', 'singlePoints',
    SymbolLayerProperties(
      filter: ['!', ['has', 'point_count']],
      iconImage: 'marker-15',
      iconSize: 1.2,
    ),
  );
}

This setup groups markers into clusters at low zooms, styles them by size, and adds labels for the cluster count. Tapping a cluster can programmatically zoom in:

controller.onFeatureTapped.add((id, point, latLng) {
  controller.animateCamera(CameraUpdate.zoomIn());
});

Enabling Offline Maps

Offline functionality in advanced Flutter Mapbox involves creating “offline packs” for a given region, style, and zoom range. Use the offlineManager on your MapboxMapController:

Future<void> downloadRegion() async {
  final bounds = LatLngBounds(
    northeast: LatLng(37.8049, -122.3894),
    southwest: LatLng(37.7449, -122.4494),
  );
  await _mapController.offlineManager.createPack(
    OfflineRegionDefinition(
      styleURL: MapboxStyles.MAPBOX_STREETS,
      bounds: bounds,
      minZoom: 10,
      maxZoom: 16,
      pixelRatio: 2.0,
    ),
    metadata: {'name': 'sf-region'},
    onProgress: (status) {
      print('Downloaded ${status.completedResourceCount}/${status.requiredResourceCount}');
    },
  );
}

Key points:

• styleURL—choose your Mapbox style (streets, satellite, custom)

• LatLngBounds—geographical region for caching

• minZoom/maxZoom—zoom levels to include

• pixelRatio—matching device DPR yields crisp tiles

Monitor download progress via the callback and handle errors in your UI. Once completed, your MapboxMap will load from the cache when offline, falling back gracefully if tiles are missing.

Tips for Performance and Reliability

• Throttle cluster updates: If your data is dynamic, debounce updates to the GeoJSON source to avoid excessive redraws.

• Limit offline region size: Large regions at high zoom can exceed storage. Prioritize critical areas or split into smaller packs.

• Clean up unused packs: Use offlineManager.listPacks() and deletePack() to reclaim space.

• Test offline behavior: Enable a network-dropped simulator/emulator to verify seamless caching.

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Conclusion

In this Flutter Mapbox advanced guide, we combined cluster rendering via GeoJSON sources with offline map packs to create a robust, high-performance map experience. Clustering reduces clutter and improves UX, while offline caching ensures your app remains functional in low- or no-network scenarios.

By following this tutorial, you’re well on your way to mastering clustering and offline maps with Mapbox in Flutter—key skills for any Flutter Mapbox advanced implementation. Explore more Mapbox style customizations, vector layers, and user interactions to elevate your map features further.