How to Implement Geotagging and Location-Based Search in FlutterFlow

1// Custom Action: getCurrentLocation
2// No parameters
3// Returns: String in format "lat,lng" (e.g. "51.5074,-0.1278")
4import 'package:geolocator/geolocator.dart';
5
6Future<String> getCurrentLocation() async {
7  LocationPermission permission = await Geolocator.checkPermission();
8  if (permission == LocationPermission.denied) {
9    permission = await Geolocator.requestPermission();
10    if (permission == LocationPermission.denied) return '';
11  }
12  if (permission == LocationPermission.deniedForever) return '';
13
14  final position = await Geolocator.getCurrentPosition(
15    desiredAccuracy: LocationAccuracy.medium,
16  );
17  return '${position.latitude},${position.longitude}';
18}

1// Custom Action: encodeGeohash
2// Parameters: latLng (String, format: "lat,lng")
3// Returns: String (geohash of length 5)
4// Simple geohash encoding — for production, use dart_geohash package
5Future<String> encodeGeohash(String latLng) async {
6  if (latLng.isEmpty) return '';
7  final parts = latLng.split(',');
8  if (parts.length != 2) return '';
9  final lat = double.tryParse(parts[0]) ?? 0.0;
10  final lng = double.tryParse(parts[1]) ?? 0.0;
11
12  // Use dart_geohash package in production:
13  // import 'package:dart_geohash/dart_geohash.dart';
14  // return GeoHasher().encode(lng, lat, precision: 5);
15
16  // Simplified placeholder — add dart_geohash to pubspec.yaml
17  return _encodeSimple(lat, lng, 5);
18}
19
20String _encodeSimple(double lat, double lng, int precision) {
21  const base32 = '0123456789bcdefghjkmnpqrstuvwxyz';
22  var minLat = -90.0, maxLat = 90.0;
23  var minLng = -180.0, maxLng = 180.0;
24  var isEven = true;
25  var bit = 0, ch = 0;
26  final result = StringBuffer();
27
28  while (result.length < precision) {
29    if (isEven) {
30      final mid = (minLng + maxLng) / 2;
31      if (lng >= mid) { ch |= (1 << (4 - bit)); minLng = mid; } else { maxLng = mid; }
32    } else {
33      final mid = (minLat + maxLat) / 2;
34      if (lat >= mid) { ch |= (1 << (4 - bit)); minLat = mid; } else { maxLat = mid; }
35    }
36    isEven = !isEven;
37    if (bit < 4) { bit++; } else { result.write(base32[ch]); bit = 0; ch = 0; }
38  }
39  return result.toString();
40}

1// Cloud Function: searchNearby
2// Query params: lat, lng, radiusKm
3const functions = require('firebase-functions');
4const admin = require('firebase-admin');
5
6exports.searchNearby = functions.https.onRequest(async (req, res) => {
7  res.set('Access-Control-Allow-Origin', '*');
8  const { lat, lng, radiusKm = 5 } = req.query;
9  if (!lat || !lng) return res.status(400).json({ error: 'lat and lng required' });
10
11  const center = [parseFloat(lat), parseFloat(lng)];
12  const radius = parseFloat(radiusKm);
13
14  // Compute geohash prefix length based on radius
15  // 5km radius -> prefix length 4, 1km -> length 5
16  const prefixLen = radius <= 1 ? 5 : radius <= 10 ? 4 : 3;
17  const centerHash = encodeGeohash(center[0], center[1], prefixLen);
18
19  // Query Firestore for documents near the center hash
20  const db = admin.firestore();
21  const snap = await db.collection('content')
22    .where('geohash', '>=', centerHash)
23    .where('geohash', '<', centerHash + '~')
24    .limit(50)
25    .get();
26
27  // Filter by exact distance (Haversine)
28  const results = snap.docs
29    .map(d => ({ id: d.id, ...d.data() }))
30    .filter(doc => {
31      const dist = haversineKm(center[0], center[1], doc.latitude, doc.longitude);
32      return dist <= radius;
33    });
34
35  res.json({ results });
36});
37
38function haversineKm(lat1, lng1, lat2, lng2) {
39  const R = 6371;
40  const dLat = (lat2 - lat1) * Math.PI / 180;
41  const dLng = (lng2 - lng1) * Math.PI / 180;
42  const a = Math.sin(dLat/2)**2 + Math.cos(lat1*Math.PI/180)*Math.cos(lat2*Math.PI/180)*Math.sin(dLng/2)**2;
43  return R * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
44}