bangladesh_geo_postcode: Offline Bangladesh Postcode Lookup in Flutter

Need to look up Bangladesh postcodes, divisions, districts, or thanas in your Flutter app — without any network calls? The bangladesh_geo_postcode package provides a fully offline, blazing-fast geographic postcode lookup powered by Protocol Buffers.

Why bangladesh_geo_postcode?

Many Bangladeshi apps need location-based features like address forms, delivery zone selection, or postcode validation. Relying on a remote API adds latency, requires connectivity, and introduces a point of failure. This package bundles the entire Bangladesh geographic hierarchy locally using protobuf for efficient binary loading, so lookups are instant and work completely offline.

Key Features

• Hierarchical location navigation: Division → District → Thana → Postcode
• Dual-language support (Bangla and English)
• O(1) postcode search — accepts both English digits (1206) and Bangla numerals (১২০৬)
• In-memory caching with a single protobuf load
• Fully offline — no network, database, or external dependencies

Installation

Add the package to your pubspec.yaml:

dependencies:
  bangladesh_geo_postcode: ^0.0.2

Then run:

flutter pub get

Getting Started

Initialize the location cache once at app startup:

import 'package:bangladesh_geo_postcode/bangladesh_geo_postcode.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await LocationCache.instance.load();
  runApp(MyApp());
}

Querying Divisions

Retrieve all divisions of Bangladesh:

final service = LocationService();

// Get all divisions
List<Division> divisions = service.getDivisions();

for (var division in divisions) {
  print('${division.name} (${division.nameBn})');
}
// Output: Dhaka (ঢাকা), Chattogram (চট্টগ্রাম), ...

Querying Districts and Thanas

Navigate the hierarchy by passing the parent division or district:

// Get districts under a division
List<District> districts = service.getDistricts(divisionId: 'dhaka');

// Get thanas under a district
List<Thana> thanas = service.getThanas(districtId: 'dhaka');

Postcode Lookup

Search for a postcode to get its full location details:

// Search with English digits
var result = service.searchPostcode('1206');

// Or with Bangla numerals
var result = service.searchPostcode('১২০৬');

if (result != null) {
  print('Division: ${result.division}');
  print('District: ${result.district}');
  print('Thana: ${result.thana}');
  print('Postcode: ${result.postcode}');
}

Real-World Use Case

Here is a practical example of a postcode search widget:

class PostcodeLookupWidget extends StatefulWidget {
  @override
  State<PostcodeLookupWidget> createState() => _PostcodeLookupWidgetState();
}

class _PostcodeLookupWidgetState extends State<PostcodeLookupWidget> {
  final _controller = TextEditingController();
  final _service = LocationService();
  String _result = '';

  void _search() {
    final location = _service.searchPostcode(_controller.text);
    setState(() {
      _result = location != null
          ? '${location.thana}, ${location.district}, ${location.division}'
          : 'Postcode not found';
    });
  }

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        TextField(
          controller: _controller,
          decoration: InputDecoration(
            labelText: 'Enter Postcode',
            suffixIcon: IconButton(
              icon: Icon(Icons.search),
              onPressed: _search,
            ),
          ),
          keyboardType: TextInputType.number,
        ),
        SizedBox(height: 16),
        Text(_result, style: TextStyle(fontSize: 16)),
      ],
    );
  }
}

Platform Support

The package works across all Flutter platforms: Android, iOS, Linux, macOS, Web, and Windows.

Summary

The bangladesh_geo_postcode package gives you instant, offline access to Bangladesh's complete geographic postcode database with bilingual support. Whether you are building a delivery app, an address form, or any location-aware feature for Bangladeshi users, this package eliminates the need for network calls and external dependencies.

Check it out on pub.dev or explore the source on GitHub.