How to Set Up Push Notifications Based on User Location in FlutterFlow

1// Custom Action: updateLocationAndToken
2// Packages: geolocator, firebase_messaging, cloud_firestore, firebase_auth
3// Return type: String
4
5Future<String> updateLocationAndToken() async {
6  // 1. Request location permission
7  LocationPermission permission = await Geolocator.checkPermission();
8  if (permission == LocationPermission.denied) {
9    permission = await Geolocator.requestPermission();
10    if (permission == LocationPermission.denied) {
11      return 'Location permission denied';
12    }
13  }
14  if (permission == LocationPermission.deniedForever) {
15    return 'Location permission permanently denied — enable in Settings';
16  }
17
18  // 2. Get current position
19  final position = await Geolocator.getCurrentPosition(
20    desiredAccuracy: LocationAccuracy.medium,
21  );
22
23  // 3. Compute GeoHash (precision 6 = ~1km accuracy)
24  final geoHash = GeoHasher().encode(
25    position.longitude,
26    position.latitude,
27    precision: 6,
28  );
29
30  // 4. Get FCM token
31  final fcmToken = await FirebaseMessaging.instance.getToken() ?? '';
32
33  // 5. Update Firestore
34  final uid = FirebaseAuth.instance.currentUser?.uid;
35  if (uid == null) return 'User not authenticated';
36
37  await FirebaseFirestore.instance.collection('users').doc(uid).update({
38    'fcmToken': fcmToken,
39    'geoHash': geoHash,
40    'lastLocation': {
41      'lat': position.latitude,
42      'lng': position.longitude,
43    },
44    'locationUpdatedAt': FieldValue.serverTimestamp(),
45  });
46
47  return 'Location updated: ${position.latitude}, ${position.longitude}';
48}

1// Firebase Cloud Function: checkGeofences
2// Scheduled: every 15 minutes
3// Deploy: firebase deploy --only functions:checkGeofences
4
5const functions = require('firebase-functions');
6const admin = require('firebase-admin');
7
8function haversineKm(lat1, lng1, lat2, lng2) {
9  const R = 6371;
10  const dLat = (lat2 - lat1) * Math.PI / 180;
11  const dLng = (lng2 - lng1) * Math.PI / 180;
12  const a = Math.sin(dLat / 2) ** 2 +
13    Math.cos(lat1 * Math.PI / 180) *
14    Math.cos(lat2 * Math.PI / 180) *
15    Math.sin(dLng / 2) ** 2;
16  return R * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
17}
18
19exports.checkGeofences = functions.pubsub
20  .schedule('every 15 minutes')
21  .onRun(async () => {
22    const db = admin.firestore();
23    const geofencesSnap = await db.collection('geofences')
24      .where('active', '==', true).get();
25
26    const usersSnap = await db.collection('users')
27      .where('fcmToken', '!=', '')
28      .where('locationUpdatedAt', '>', new Date(Date.now() - 30 * 60 * 1000))
29      .get();
30
31    const batch = [];
32    geofencesSnap.forEach(geofence => {
33      const g = geofence.data();
34      usersSnap.forEach(user => {
35        const u = user.data();
36        if (!u.lastLocation) return;
37        const dist = haversineKm(
38          g.centerLat, g.centerLng,
39          u.lastLocation.lat, u.lastLocation.lng
40        );
41        if (dist <= g.radiusKm && u.fcmToken) {
42          batch.push(
43            admin.messaging().send({
44              token: u.fcmToken,
45              notification: {
46                title: g.notificationTitle,
47                body: g.notificationBody,
48              },
49              data: { geofenceId: geofence.id },
50            })
51          );
52        }
53      });
54    });
55
56    await Promise.allSettled(batch);
57    return null;
58  });