android - 我是否需要扩展 FirebaseInstanceIdService 才能订阅 FCM 主题？

Question

我想从客户端(android 应用程序)管理主题订阅。我目前正在 onCreate() Activity 中进行。我想知道正确的方法是在 InstanceIdService::onTokenRefresh() 或任何方便的时间(点击按钮等)订阅/取消订阅。

简而言之，如果我在客户端管理主题订阅(没有服务器)，我还需要为 InstanceIdService 操心吗？

不同来源的文档提供了对 Firebase 云消息传递 (FCM) 主题订阅的不同看法。有些人提到了 InstanceIdService，有些人没有。他们在这里:

1. 关于 Send Topic Messages with Firebase Console 的 Firebase 指南

在谈到主题订阅时，它没有提到 InstanceIdService。

Once you've completed the setup tasks, you can add client code to subscribe to a topic and then handle messages sent to the topic.

Client apps can subscribe to any existing topic, or they can create a new topic. When a client app subscribes to a new topic name (one that does not already exist for your Firebase project), a new topic of that name is created in FCM and any client can subsequently subscribe to it.

To subscribe to a topic, the client app calls Firebase Cloud Messaging subscribeToTopic() with the FCM topic name:

FirebaseMessaging.getInstance().subscribeToTopic("news");

1. Firebase Android Codelab

The class MyFirebaseInstanceIdService will be a service used to handle FCM logic. This service is used to alert the application when a new InstanceID token is generated, and to retrieve the generated token.

Modify it to extend FirebaseInstanceIdService and override the onTokenRefresh method to subscribe to a topic. Use the following code to update the onTokenRefresh method in MyFirebaseInstanceIdService to look like this:

public class MyFirebaseInstanceIdService extends FirebaseInstanceIdService {

   private static final String TAG = "MyFirebaseIIDService";
   private static final String FRIENDLY_ENGAGE_TOPIC = "friendly_engage";

   /**
    * The Application's current Instance ID token is no longer valid 
    * and thus a new one must be requested.
    */
   @Override
   public void onTokenRefresh() {
       // If you need to handle the generation of a token, initially or
       // after a refresh this is where you should do that.
       String token = FirebaseInstanceId.getInstance().getToken();
       Log.d(TAG, "FCM Token: " + token);

       // Once a token is generated, we subscribe to topic.
       FirebaseMessaging.getInstance()
               .subscribeToTopic(FRIENDLY_ENGAGE_TOPIC);
   }
}

1. Firebase quickstart project on github

它使用 InstanceIdService，但主题订阅不会在那里发生。它作为 Activity 中按钮单击的一部分在客户端中简单地完成:

Button subscribeButton = (Button) findViewById(R.id.subscribeButton);
subscribeButton.setOnClickListener(new View.OnClickListener() {
    @Override
    public void onClick(View v) {
        // [START subscribe_topics]
        FirebaseMessaging.getInstance().subscribeToTopic("news");
        // [END subscribe_topics]

        // Log and toast
        String msg = getString(R.string.msg_subscribed);
        Log.d(TAG, msg);
        Toast.makeText(MainActivity.this, msg, Toast.LENGTH_SHORT).show();
    }
});

InstanceIdService 代码处的注释建议管理器订阅 onTokenRefresh()

@Override
public void onTokenRefresh() {
    // Get updated InstanceID token.
    String refreshedToken = FirebaseInstanceId.getInstance().getToken();
    Log.d(TAG, "Refreshed token: " + refreshedToken);

    // If you want to send messages to this application instance or
    // manage this apps subscriptions on the server side, send the
    // Instance ID token to your app server.
    sendRegistrationToServer(refreshedToken);
}

Answer 1

如您所知，FirebaseInstanceId 可能是一个单例类，您可以在其中检索注册 token 。所以我认为 subscribeToTopic() 方法，因为只传递了主题的名称，你可以假设它已经调用了 FirebaseInstanceId 本身的实例，或者只是发送在向具有相应注册 token 的 FCM 服务器发出的请求中，以及它应该订阅的主题。

长话短说，我认为您不需要扩展 FirebaseInstanceIdService 来调用 subscribeToTopic()，但是，我认为这是必不可少的，因为(如 docs 中所述)它是:

Base class to handle Firebase Instance ID token refresh events.

---

对于您的其他查询。

I want to manage topic subscription from the client (Android app). I am currently doing it at activity onCreate(). I am wondering if the right way is to subscribe / unsubscribe at InstanceIdService::onTokenRefresh() or at any time convenient (on button click, etc)?

我认为在 onCreate() 中执行它是可以的。如果你看到我的回答here ，@FrankvanPuffelen 提到:

subscribing to topics on app start is fine.

但是，我认为在 onTokenRefresh() 中添加一个 subscribeToTopic() 调用也很好，这样一旦为应用程序提供新 token 例如，您将立即相应地订阅它。

注意 我在这里想到的行为是，当注册 token 失效时，它的订阅也会丢失，并且在 onRefreshToken 中添加 subscribeToTopic() () 将立即为您重新订阅它们(当然，这仍然取决于您要订阅哪个主题的实现)。