Flutter Address Autocomplete for Vietnam (suggest + resolve)

Flutter app
  -> your backend proxy  /address/suggest   (adds X-API-Key)
       -> GoGoDuk  /v1/suggest        -> predictions
  (user picks a suggestion)
  -> your backend proxy  /address/resolve    (adds X-API-Key)
       -> GoGoDuk  /v1/place/resolve  -> coordinates + clean address

import 'dart:convert';
import 'package:http/http.dart' as http;
 
class Prediction {
  final String placeId;
  final String mainText;
  final String secondaryText;
  Prediction({
    required this.placeId,
    required this.mainText,
    required this.secondaryText,
  });
  factory Prediction.fromJson(Map<String, dynamic> j) => Prediction(
        placeId: j['placeId'] as String,
        mainText: (j['mainText'] ?? j['text'] ?? '') as String,
        secondaryText: (j['secondaryText'] ?? '') as String,
      );
}
 
class AddressApi {
  // YOUR proxy — do NOT point straight at api.gogoduk.com from the app.
  static const _base = 'https://your-backend.example.com';
 
  static Future<List<Prediction>> suggest(
    String input, {
    String? sessionToken,
  }) async {
    if (input.trim().length < 2) return [];
    final uri = Uri.parse('$_base/address/suggest').replace(
      queryParameters: {
        'input': input,
        'lang': 'vi',
        'country': 'VN',
        if (sessionToken != null) 'sessionToken': sessionToken,
      },
    );
    final res = await http.get(uri);
    if (res.statusCode != 200) return [];
    final data = jsonDecode(res.body) as Map<String, dynamic>;
    final list = (data['predictions'] as List?) ?? [];
    return list
        .map((e) => Prediction.fromJson(e as Map<String, dynamic>))
        .toList();
  }
}

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:uuid/uuid.dart';
 
class AddressField extends StatefulWidget {
  final void Function(Prediction) onSelected;
  const AddressField({super.key, required this.onSelected});
  @override
  State<AddressField> createState() => _AddressFieldState();
}
 
class _AddressFieldState extends State<AddressField> {
  final _controller = TextEditingController();
  Timer? _debounce;
  List<Prediction> _results = [];
  String _sessionToken = const Uuid().v4();
 
  void _onChanged(String value) {
    _debounce?.cancel();
    _debounce = Timer(const Duration(milliseconds: 300), () async {
      final preds =
          await AddressApi.suggest(value, sessionToken: _sessionToken);
      if (mounted) setState(() => _results = preds);
    });
  }
 
  @override
  void dispose() {
    _debounce?.cancel();
    _controller.dispose();
    super.dispose();
  }
 
  @override
  Widget build(BuildContext context) {
    return Column(
      crossAxisAlignment: CrossAxisAlignment.start,
      children: [
        TextField(
          controller: _controller,
          onChanged: _onChanged,
          decoration: const InputDecoration(
            hintText: 'Enter delivery address…',
            border: OutlineInputBorder(),
          ),
        ),
        ..._results.map(
          (p) => ListTile(
            title: Text(p.mainText),
            subtitle: Text(p.secondaryText),
            onTap: () {
              _controller.text = '${p.mainText}, ${p.secondaryText}';
              setState(() => _results = []);
              widget.onSelected(p);
              // Session ends on pick → rotate the token for the next round.
              _sessionToken = const Uuid().v4();
            },
          ),
        ),
      ],
    );
  }
}

class ResolvedPlace {
  final double lat;
  final double lon;
  final String address;
  ResolvedPlace({required this.lat, required this.lon, required this.address});
  factory ResolvedPlace.fromJson(Map<String, dynamic> r) => ResolvedPlace(
        lat: (r['lat'] as num).toDouble(),
        lon: (r['lon'] as num).toDouble(),
        address: (r['address'] ?? r['name'] ?? '') as String,
      );
}
 
Future<ResolvedPlace?> resolvePlace(
  String placeId, {
  String? sessionToken,
}) async {
  final uri = Uri.parse('https://your-backend.example.com/address/resolve')
      .replace(queryParameters: {
    'id': placeId,
    'lang': 'vi',
    if (sessionToken != null) 'sessionToken': sessionToken,
  });
  final res = await http.get(uri);
  if (res.statusCode != 200) return null;
  final data = jsonDecode(res.body) as Map<String, dynamic>;
  final result = data['result'] as Map<String, dynamic>?;
  if (result == null) return null;
  return ResolvedPlace.fromJson(result);
}

AddressField(
  onSelected: (pred) async {
    final place = await resolvePlace(pred.placeId);
    if (place != null) {
      debugPrint('Coordinates: ${place.lat}, ${place.lon}');
      // map.move(LatLng(place.lat, place.lon), 16); ...
    }
  },
)