Masamune Location Geocoding

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Masamune Location Geocoding

Overview

masamune_location_geocoding provides geocoding and reverse geocoding functionality for Masamune apps via Cloud Functions. Convert between coordinates and addresses.

Note: Requires masamune_location for core location functionality.

Usage

Installation

flutter pub add masamune_location
flutter pub add masamune_location_geocoding

Register the Adapter

Configure GeocodingMasamuneAdapter with a Functions adapter for backend integration.

// lib/adapter.dart

import 'package:masamune_location_geocoding/masamune_location_geocoding.dart';
import 'package:katana_functions_firebase/katana_functions_firebase.dart';

final functionsAdapter = FirebaseFunctionsAdapter(
  options: DefaultFirebaseOptions.currentPlatform,
  region: FirebaseRegion.asiaNortheast1,
);

/// Masamune adapters used in the application.
final masamuneAdapters = <MasamuneAdapter>[
  const UniversalMasamuneAdapter(),

  GeocodingMasamuneAdapter(
    functionsAdapter: functionsAdapter,
  ),
];

Reverse Geocoding (Coordinates → Address)

Convert latitude/longitude to a human-readable address:

class GeocodingPage extends PageScopedWidget {
  @override
  Widget build(BuildContext context, PageRef ref) {
    final geocoding = GeocodingMasamuneAdapter.primary;

    return ElevatedButton(
      onPressed: () async {
        try {
          final address = await geocoding.fromLatLng(
            latitude: 35.6812,
            longitude: 139.7671,
          );
          
          print("Address: $address");
          // e.g., "Tokyo Station, Tokyo, Japan"
        } catch (e) {
          print("Geocoding failed: $e");
        }
      },
      child: const Text("Get Address"),
    );
  }
}

Geocoding (Address → Coordinates)

Convert an address to latitude/longitude:

final coordinates = await geocoding.fromAddress("Tokyo Station, Japan");

print("Lat: ${coordinates.latitude}, Lng: ${coordinates.longitude}");

Backend Implementation

Your Cloud Functions must implement the geocoding actions using an external API (e.g., Google Maps Geocoding API):

// Cloud Functions
import * as functions from 'firebase-functions';
import axios from 'axios';

export const geocoding = functions.https.onCall(async (data, context) => {
  const GOOGLE_MAPS_API_KEY = process.env.GOOGLE_MAPS_API_KEY;
  
  if (data.action === "geocoding") {
    const { latitude, longitude, address } = data;
    
    if (latitude && longitude) {
      // Reverse geocoding (coordinates -> address)
      const response = await axios.get(
        `https://maps.googleapis.com/maps/api/geocode/json`,
        {
          params: {
            latlng: `${latitude},${longitude}`,
            key: GOOGLE_MAPS_API_KEY,
          },
        }
      );
      
      return {
        address: response.data.results[0]?.formatted_address,
      };
    }
    
    if (address) {
      // Geocoding (address -> coordinates)
      const response = await axios.get(
        `https://maps.googleapis.com/maps/api/geocode/json`,
        {
          params: {
            address: address,
            key: GOOGLE_MAPS_API_KEY,
          },
        }
      );
      
      const location = response.data.results[0]?.geometry?.location;
      return {
        latitude: location.lat,
        longitude: location.lng,
      };
    }
  }
});

Tips

• Store Google Maps API key securely using environment variables
• Implement rate limiting in your backend to prevent API quota exhaustion
• Cache frequently requested addresses to reduce API calls
• Handle errors gracefully when geocoding fails (e.g., invalid address)

GitHub Sponsors

Sponsors are always welcome. Thank you for your support!

https://github.com/sponsors/mathrunet