FCM通知负载 - 在应用未运行时确定主题名称

Question

Backend server sends FCM notification like this:

{
  "to": "/topics/599_7041",
  "priority": "high",
  "data": {
    "id_message": "45" 
  }
  "click_action": "SHOW" 
  "notification" : {
      "body" : "Lorem ipsum",
      "title" : "Sample" 
    }
}

My application subscribes multiple topics. When application is not running, Firebase displays notification and allows me to run app after tap on notification message, with provided click action and pass data (in this case, message_id ) to launched app instance.

Good so far. However, in addition, I need to determine from which subscribed topic notification is received. Can I determine it somehow when launching new app instance from notification, or I need to add topic name to data (next to message_id )?

I know I can determine to filed when my app is running, this way:

@Override
public void onMessageReceived(@NonNull final RemoteMessage remoteMessage)
{
 //....
 String to = remoteMessage.getTo();
}

But, what if my app is not running, so onMessageReceived won't be called.

Answer 1

you can do this:

exports.pushNotification =
functions.database.ref('/messages/{pushId}').onWrite( event => {

console.log('Push notification event triggered');


var valueObject = event.data.val();

console.log("it is"+ valueObject.title);
//Create a notification
const payload = {
 notification: {
    title:valueObject.title,
    body: valueObject.message,
    sound: "default"
},
};

This way you are using the database trigger onWrite , that checks if any messages have been written under the pushid .

Then you retreive the data from the database using: var valueObject = event.data.val(); .

And in the notification{..} you can use valueObject.title which will be the topic name, thus when recieving a notification, the topic name will be in the title of the notification and thats how you can know what topic it is.

For more info check https://firebase.google.com/docs/functions/database-events