在应用关闭时收听Firebase数据库更改 [英] Listen to firebase database changes when app is closed

问题描述

我正在使用Firebase创建一个Ionic 2应用程序，并且我需要一种方法来关闭该应用程序(即在前台，背景中并被杀死)时监听数据库更改(特别是在child_added上)

I am creating an Ionic 2 app with firebase and I need a way to listen to database changes (specifically on child_added) when the app is closed (I.e. in foreground,background and killed)

基本上，我想使用WebRTC在类似whatsapp的应用程序内拨打电话，而我正在关注此帖子-

Basically, I want to use WebRTC to make calls within the app like whatsapp and I am following this post - https://websitebeaver.com/insanely-simple-webrtc-video-chat-using-firebase-with-codepen-demo

但是，唯一令我困惑的是应用程序关闭时它将如何工作.谁能帮我理解吗?

However, the only thing that puzzles me is how it will work when the app is closed. Can anyone please help me understand?

谢谢！

推荐答案

使用Firebase客户端SDK不能以与应用程序代码运行时完全相同的方式来主动侦听数据库更改.

It's not possible to actively listen to database changes using the Firebase client SDK in exactly the same way that you can when your app's code is running.

如果您希望您的应用程序接收有关数据库更改的信息，则可以改用 Firebase Cloud Messaging ，向您的应用发送一条通知，其中包含较小的有效负载，其中包含有关更改的信息.您的应用收到通知后，便可以决定要做什么. 网络支持存在一些限制，因此请务必阅读那个.

If you want your app to receive information about changes to your database, you can instead use Firebase Cloud Messaging to send your app a notification with a small payload that contains information about the change. When your app receives the notification, it can then make a decision about what to do. There are some limitations with web support, so be sure to read about that.

还可以查看 Firebase的云功能，以便更轻松地编写一些服务器端可以响应数据库更改而触发的代码，并在发生这些更改时发送通知.

Also look into Cloud Functions for Firebase to make it easier to write some server side code that can trigger in response to a database change and send a notification when those changes happen.

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