Firestore metadata get method doesn't succed

问题

I have an issue with Firebase's Firestore in my app, based on a MVVM architecture. When I try to get an object from a document reference, the addOnCompleteListener never succed (neither the other listeners). Here is my code of ItemRepo.kt in which I call the get method to my document reference.

NOTE: myDocRef is used in the init of the viewModel (called by the getMyItems method that returns a Query objcet that I observe with a snapshotListener) and is ordered by those two fields. I've tried to use directly that reference and also a new one, local in the function getMyItem

private val myDocRef = db.collection("users").document(userAuth!!.uid).collection("myitems")
...

fun getMyItems() : Query {
    return myDocRef.orderBy("title", Query.Direction.ASCENDING)
        .orderBy("expiryDate", Query.Direction.DESCENDING)
}

...

fun getMyItem(adId : String) : Item {
    var item : Item? = null
    /*val docRef = db.collection("users").document(userAuth!!.uid)
        .collection("myitems").document(adId)*/
    /*the previous code was just a try
    **to use non ordered collection
    * no success!*/
    myDocRef.document(adId)
        .get().addOnCompleteListener { task ->
            if (task.isSuccessful) {
                item = task.result!!.toObject(Item::class.java)!!
            } else {
                Log.d("firestore","get KO!")
            }
        }
    return item!!
}

I've also tried to write manually the adId to match one of the documents in that collection, without positive results... I need the return value of that function (the object contained in that document) outside but I'm stuck here.

NOTE: I have another repository in which I manage the user document in the same way and everything works perfectly

EDITED: maybe could it happen because I already have a listener on the collection which I want to get only one document from?

来源：https://stackoverflow.com/questions/61843756/firestore-metadata-get-method-doesnt-succed