发送推送通知的条件应该放在哪里？

Question

我想构建一个应用程序，例如当我将带有纬度和经度信息的新数据保存到 Firebase 时，然后在我的应用程序中计算这些纬度和经度与用户当前位置之间的距离。如果距离小于 60 公里，则发送onBackgroundMessage 通知。我不会将用户的当前位置存储在 firebase 上。我使用函数_getCurrentLocation 获取用户的当前位置。 问题是我不知道在哪里以及如何放置isValidDistance 来检查距离是否低于 60 公里。 目前我的应用会发送通知，但不是按距离发送通知。

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

首先，您需要将 fcm 从通知消息更改为数据消息，以允许应用在后台处理消息。检查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,
    },
  });
});

选中here 以在应用打开时显示推送通知。你的代码应该是这样的。

FirebaseMessaging.onMessage.listen((RemoteMessage message) {
if (isValidDistance(message)) {
    print('onMessageListen');
    showNotification(message);
  }
});

您可以通过以下方式访问发送的数据

Map<String, dynamic> data = message.data;

那么后台处理程序如下。

_messageHandler(RemoteMessaging message){
if (isValidDistance(message)) {
        print('onMessageListen');
        showNotification(message);
      }
}

或者如下创建一个 Notification 类并使用。

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),
        ),
      );
    }
  }
}