Where should put the condition to send push notification in flutter? - firebase

Question

I would like to build an app like when I save a new data with latitude and longitude information to firebase then in my app I calculate the distance between these latitude&longitude and the user's current location. If the distance is less than 60 kilometres then send an onBackgroundMessage notification. I do not store the user's current location on firebase. I get the user's current location with function _getCurrentLocation.
The problem is that I do not undertsand where and how to put the isValidDistance to check if the distance is under 60 kilimetres.
Currently my app send notifications but not by distance.
index.js
const functions = require("firebase-functions");
const admin = require("firebase-admin");
admin.initializeApp();
exports.myFunction = functions.firestore
.document("animal/{message}")
.onCreate((snapshot, context) => {
return admin.messaging().sendToTopic("animal", {
data: {
latitude: snapshot.data()["latitude"].toString(),
longitude: snapshot.data()["longitude"].toString(),
},
notification: {
title: snapshot.data().username,
body: snapshot.data().description,
clickAction: "FLUTTER_NOTIFICATION_CLICK",
},
});
});
main.dart
Future<void> _messageHandler(RemoteMessage message) async {
print('background message ${message.data}');
}
void main() async {
WidgetsFlutterBinding.ensureInitialized();
await Firebase.initializeApp();
runApp(MyApp());
}
class MyApp extends StatefulWidget {
#override
_MyAppState createState() => _MyAppState();
}
class _MyAppState extends State<MyApp> {
double? currentLatitude;
double? currentLongitude;
Future<void> _getCurrentLocation() async {
final locData = await Location().getLocation();
setState(() {
currentLatitude = locData.latitude;
currentLongitude = locData.longitude;
});
}
int getDistanceInMeters(currLat, currLng, lat, lng) {
return Geolocator.distanceBetween(
currLat,
currLng,
lat,
lng,
).round();
}
bool isValidDistance(RemoteMessage messaging) {
Map<String, dynamic> data = messaging.data;
var _list = data.values.toList();
var lat = double.parse(_list[0]);
var lng = double.parse(_list[1]);
print(_list);
int distance =
getDistanceInMeters(currentLatitude, currentLongitude, lat, lng);
var distanceInKm = (distance / 1000).round();
print('Distance is: ${distanceInKm.toString()}');
if (distance < 60000) {
return true;
}
return false;
}
#override
void initState() {
super.initState();
_getCurrentLocation();
final messaging = FirebaseMessaging.instance;
messaging.subscribeToTopic('animal');
FirebaseMessaging.onMessage.listen((RemoteMessage message) {
if (isValidDistance(message)) {
print('onMessageListen');
}
});
FirebaseMessaging.onMessageOpenedApp.listen((message) {
if (isValidDistance(message)) {
print('onMessageOpened');
}
});
FirebaseMessaging.onBackgroundMessage(_messageHandler);
}
...

Answer 1

First you need to change your fcm from notification message to data message to allow app handle messages while in background. Check here.
exports.myFunction = functions.firestore
.document("animal/{message}")
.onCreate((snapshot, context) => {
return admin.messaging().sendToTopic("animal", {
data: {
latitude: snapshot.data()["latitude"].toString(),
longitude: snapshot.data()["longitude"].toString(),
title: snapshot.data().username,
body: snapshot.data().description,
},
});
});
Check here to show push notification while app is open. Your code should like this.
FirebaseMessaging.onMessage.listen((RemoteMessage message) {
if (isValidDistance(message)) {
print('onMessageListen');
showNotification(message);
}
});
Yo can access the data sent through the following
Map<String, dynamic> data = message.data;
Then the background handler will be as follows.
_messageHandler(RemoteMessaging message){
if (isValidDistance(message)) {
print('onMessageListen');
showNotification(message);
}
}
Or create a Notification class as follows and use.
import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:flutter/material.dart';
import 'package:flutter_local_notifications/flutter_local_notifications.dart';
import 'package:geolocator/geolocator.dart';
import 'package:location/location.dart';
const AndroidNotificationChannel channel = AndroidNotificationChannel(
'high_importance_channel', // id
'High Importance Notifications', // title
description: 'This channel is used for important notifications.',
importance: Importance.max,
);
Future<LocationData> _getCurrentLocation() => Location().getLocation();
int getDistanceInMeters(currLat, currLng, lat, lng) {
return Geolocator.distanceBetween(
currLat,
currLng,
lat,
lng,
).round();
}
Future<bool> isValidDistance(RemoteMessage messaging) async {
Map<String, dynamic> data = messaging.data;
var _list = data.values.toList();
var lat = double.parse(_list[0]);
var lng = double.parse(_list[1]);
print(_list);
var location = await _getCurrentLocation();
int distance =
getDistanceInMeters(location.latitude, location.longitude, lat, lng);
var distanceInKm = (distance / 1000).round();
print('Distance is: ${distanceInKm.toString()}');
if (distance < 60000) {
return true;
}
return false;
}
class NotificationServices {
final flutterLocalNotificationsPlugin = FlutterLocalNotificationsPlugin();
Future<void> firebaseMessagingBackgroundHandler(RemoteMessage message) async {
bool isValid = await isValidDistance(message);
if (isValid) {
print('onMessageListen');
showNotification(message);
}
}
backgroundNotification() {
final FlutterLocalNotificationsPlugin _flutterLocalNotificationsPlugin =
FlutterLocalNotificationsPlugin();
final AndroidInitializationSettings _initialzationSettingsAndriod =
AndroidInitializationSettings('#mipmap/ic_launcher');
final IOSInitializationSettings _initialzationSettingsIOS =
IOSInitializationSettings();
final InitializationSettings _initializationSettings =
InitializationSettings(
android: _initialzationSettingsAndriod,
iOS: _initialzationSettingsIOS);
_flutterLocalNotificationsPlugin
.resolvePlatformSpecificImplementation<
AndroidFlutterLocalNotificationsPlugin>()
?.createNotificationChannel(channel);
/// Update the iOS foreground notification presentation options to allow
/// heads up notifications.
FirebaseMessaging.instance.setForegroundNotificationPresentationOptions(
alert: true,
badge: true,
sound: true,
);
_flutterLocalNotificationsPlugin.initialize(_initializationSettings);
FirebaseMessaging.instance
.getInitialMessage()
.then((RemoteMessage? message) async {
if (message != null) await onClickNotificationHandler(message);
});
FirebaseMessaging.onMessage.listen((RemoteMessage message) async {
bool isValid = await isValidDistance(message);
if (isValid) {
print('onMessageListen');
showNotification(message);
}
});
FirebaseMessaging.onBackgroundMessage(firebaseMessagingBackgroundHandler);
FirebaseMessaging.onMessageOpenedApp.listen((RemoteMessage message) async {
await onClickNotificationHandler(message);
});
}
onClickNotificationHandler(RemoteMessage message) async {
Map<String, dynamic> data = message.data;
print(data);
//you can handle notificationand navigate to necessary screen here.
}
showNotification(RemoteMessage message) {
Map<String, dynamic> data = message.data;
if (data["body"] != null) {
flutterLocalNotificationsPlugin.show(
data.hashCode,
data["title"],
data["body"],
NotificationDetails(
android: AndroidNotificationDetails(
channel.id,
channel.name,
channelDescription: channel.description,
icon: '#mipmap/ic_launcher',
),
iOS: IOSNotificationDetails(
presentAlert: true, presentBadge: true, presentSound: true),
),
);
}
}
}