[FCM] firebase常見q&a

1. Do I have to unsubscribe the old token and subscribe the new token to topics?

AFAIK, you don't have to unsubscribe the old token, since it will be discarded by FCM itself. For the new token, yes, you'll have to subscribe it to the topic you need. The usual thing is done (in Android) by having subscribeToTopic() in onTokenRefreshed().

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2. Do I have to remove the old token and add the new token to device groups?

Yes. You have to handle the mapping/relationships for Device Group Messaging. See my answer here. This is different from topics. The token will be invalidated, but will be kept as part of the list of registration tokens for the corresponding registration key.

It's why there's a possibility to receive a NotRegistred error on one of the tokens if you send to Device Group. :)

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3. Is it possible to get information about device groups/topics for a token?

For Device Group Messaging (same with #2), the developer (you) have to manage these details yourself. For topics, you can use the InstanceID API. Specifically, set details parameter to true:

[optional] boolean details: set this query parameter to true to get available IID token details, including connection information and FCM or GCM topic subscription information (if any) for the device associated with this token. When not specified, defaults to false.

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4. Can I add a token to a device group more than once?

Ahmm. Yes. Do you mean the same token? If so, I haven't tried it yet. Might as well do some checking on the client side before adding.

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5. Can I subscribe a token to a topic more than once?

If you mean re-subscribing, then yes. If you mean duplicate request to subscribe, I think the result would still be a success. No changes in behavior though.

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6. Will multiple subscriptions/additions of the same token result in receiving duplicate messages?

Tested it out. You won't receive duplicate messages for both duplicate topic subscriptions and adding the same token to a device group. It seems that FCM ignores the request to subscribe/add a Registration token if it's already subscribed/added to a device group.

[FCM] firebase admin 初探筆記: 從backend丟訊息

記錄一下nodejs使用FCM Admin的相關筆記，
主要要透過自已的backend與fcm做溝通，
跟web notification無關。

1. 安裝

npm install firebase-admin --save

2. Firebase開專案

3. 設定金鑰

專案設定頁->點擊服務帳戶的Tab->產生新的私密金鑰

4. 初始化SDK

var admin = require('firebase-admin');
var serviceAccount = require('path/to/serviceAccountKey.json');

admin.initializeApp({
  credential: admin.credential.cert(serviceAccount),
  databaseURL: 'https://.firebaseio.com'
});

當然如果不要透過下載.json，也是可以用變數的方式做初始化。

5. 發送訊息 send()

接著就可以透過admin.messaging()內的send方法發送訊息

// The topic name can be optionally prefixed with "/topics/".
var topic = 'highScores';
// See documentation on defining a message payload.
var message = {
  data: {
    score: '850',
    time: '2:45'
  },
  topic: topic};
// Send a message to devices subscribed to the provided topic.
admin.messaging().send(message)
  .then((response) => {
    // Response is a message ID string.
    console.log('Successfully sent message:', response);
  })
  .catch((error) => {
    console.log('Error sending message:', error);
  });

也可以在send方法內使用測試模式

admin.messaging().send(message, dryRun)

指定條件的訊息

在message也可以加condition

// Define a condition which will send to devices which are subscribed
// to either the Google stock or the tech industry topics.
var condition = "'stock-GOOG' in topics || 'industry-tech' in topics";
// See documentation on defining a message payload.
var message = {
  notification: {
    title: '$GOOG up 1.43% on the day',
    body: '$GOOG gained 11.80 points to close at 835.67, up 1.43% on the day.'
  },
  condition: condition};
// Send a message to devices subscribed to the combination of topics
// specified by the provided condition.
admin.messaging().send(message)
  .then((response) => {
    // Response is a message ID string.
    console.log('Successfully sent message:', response);
  })
  .catch((error) => {
    console.log('Error sending message:', error);
  });

定義訊息

透過fcm可以推播包含webpush/apns(iOS)/android等消息。

一個封裝訊息的欄位參數

参数	说明
data	键值对映射，其中所有键和值都是字符串。
notification	一个包含 title 和 body 字段的对象。
android	一个由 Android 消息专用字段组成的对象。要了解详情，请参阅 Android 专用字段。
apns	一个由 Apple 推送通知服务 (APNS) 专用字段组成的对象。要了解详情，请参阅 APNS 专用字段。
webpush	一个由 WebPush 协议专用字段组成的对象。要了解详情，请参阅 WebPush 专用字段。
token	一个用于标识消息的收件人设备的注册令牌。
topic	要将消息发送至的主题名称。该主题名称不能包含 /topics/ 前缀。
condition	发送消息时所依据的条件，例如 "foo" in topics && "bar" in topics

綜合的訊息

以下是一個主題的推播，並推發到andriod/apns

var message = {
  notification: {
    title: '$GOOG up 1.43% on the day',
    body: '$GOOG gained 11.80 points to close at 835.67, up 1.43% on the day.',
  },
  android: {
    ttl: 3600 * 1000,
    notification: {
      icon: 'stock_ticker_update',
      color: '#f45342',
    },
  },
  apns: {
    payload: {
      aps: {
        badge: 42,
      },
    },
  },
  topic: 'industry-tech'
};




常見授權錯誤

如果你在send訊息出現以下錯誤，

Credential implementation provided to initializeApp() via the \"credential\" property failed to fetch a valid Google OAuth2 access token with the following error

通常都是你目前環境的時間跟FCM的不一致，

只要同步時間就好了，

$>sudo service ntp restart

官方文件

https://firebase.google.com/docs/admin/setup?authuser=2
https://firebase.google.com/docs/cloud-messaging/admin/send-messages?authuser=1