当firebase RTDB发生变化时通知GET

Question

我一直在寻找一种在Firebase实时数据库发生变化时收到通知的方法。 最后我找到了这个解决方案（下面的链接），但是这个方法适用于Firestore，而不是数据库。 我真的无法更改它以使其在Firebase数据库而不是Firestore上运行。 有人可以帮我这个吗？这对我来说非常重要。 我是打字稿/ firebase的新手。

感谢。

link：https://angularfirebase.com/lessons/send-push-notifications-in-angular-with-firebase-cloud-messaging/

我的数据库：

page index.ts：

import * as functions from 'firebase-functions';

import * as admin from 'firebase-admin';
admin.initializeApp(functions.config().firebase);


exports.newSubscriberNotification = functions.firestore
.document('subscribers/{subscriptionId}')
.onCreate(async event => {

const data = event.data()

const userId = data.userId
const subscriber = data.subscriberId

// Notification content
const payload = {
    notification: {
        title: 'New Subscriber',
        body: `${subscriber} is following your content!`,
        icon: 'link to icon'
    }
}

// ref to the parent document
const db = admin.firestore()
const devicesRef = db.collection('devices').where('userId', '==', userId)


// get users tokens and send notifications

const devices = await devicesRef.get()

const tokens = []

devices.forEach(result => {
    const token = result.data().token;

   tokens.push( token )
})

return admin.messaging().sendToDevice(tokens, payload)

});

提供者fcm.ts​​：

import { HttpClient } from '@angular/common/http';
import { Injectable } from '@angular/core';
import { Firebase } from '@ionic-native/firebase';
import { Platform } from 'ionic-angular';
import { AngularFirestore } from 'angularfire2/firestore';


@Injectable()
export class FcmProvider {

constructor(
public firebaseNative: Firebase,
public afs: AngularFirestore,
private platform: Platform
) {


}

async getToken() {

let token;

if (this.platform.is('android')) {

  token = await this.firebaseNative.getToken()
} 

if (this.platform.is('ios')) {
  token = await this.firebaseNative.getToken();
  const perm = await this.firebaseNative.grantPermission();
} 

// Is not cordova == web PWA
if (!this.platform.is('cordova')) {
  // TODO add PWA support with angularfire2
} 

return this.saveTokenToFirestore(token)
}

private saveTokenToFirestore(token) {
if (!token) return;
const devicesRef = this.afs.collection('devices');

const docData = { 
  token,
  userId: 'testUser',
}

return devicesRef.doc(token).set(docData)
}

listenToNotifications() {
return this.firebaseNative.onNotificationOpen()
}

}

最后是home.ts页面：

import { Component } from '@angular/core';
import { NavController } from 'ionic-angular';
import { FcmProvider } from '../../providers/fcm/fcm';

import { ToastController } from 'ionic-angular';
import { Subject } from 'rxjs/Subject';
import { tap } from 'rxjs/operators';

@Component({
selector: 'page-home',
templateUrl: 'home.html'
})
export class HomePage {

constructor(public fcm: FcmProvider, public toastCtrl: ToastController) {} 

ionViewDidLoad(){

// Get a FCM token
this.fcm.getToken()

this.fcm.listenToNotifications().pipe(
  tap(msg => {
    const toast = this.toastCtrl.create({
      message: msg.body,
      duration: 3000
    });
    toast.present();
  })
)
.subscribe()
}

}

ps：此解决方案与Firestore完美配合。