all-together.kt

val teamsQuery get() = "owners.${uid!!}".let {
    FirebaseFirestore.getInstance().collection("teams").whereGreaterThanOrEqualTo(it, 0).orderBy(it)
}

object TeamsLiveData : LiveData<ObservableSnapshotArray<T>>(), FirebaseAuth.AuthStateListener {
    init {
        FirebaseAuth.getInstance().addAuthStateListener(this)
    }

    override fun onAuthStateChanged(auth: FirebaseAuth) {
        value?.removeAllListeners()
        value = if (auth.currentUser == null) null else FirestoreArray(teamsQuery) { snapshot ->
            // I'm too lazy, but this could be optimized to not use reflection
            snapshot.toObject(Team::class.java).apply { id = snapshot.id }
        }
    }
}

// In your Activity's onCreate() or your Fragment's onViewCreated()
TeamsLiveData.observe(this, Observer { snapshots ->
    adapter?.stopListening() // Clean up after ourselves
    lifecycle.removeObserver(adapter) // Prevent Architecture Components from automatically re-subscribing an adapter
    if (snapshots == null) {
        // Not signed-in, show emtpy state
    } else {
        // Signed-in, let's init our adapter
        val options = FirestoreRecyclerOptions.Builder<Team>()
                .setSnapshotArray(snapshots)
                .setLifecycleOwner(this)
                .build()
        adapter = object : FirestoreRecyclerAdapter<Team, TeamViewHolder>(options) {
            override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): TeamViewHolder =
                    TeamViewHolder(LayoutInflater.from(parent.context)
                            .inflate(R.layout.team_list_row_layout, parent, false))

            override fun onBindViewHolder(teamHolder: TeamViewHolder, position: Int, team: Team) {
                // Bind your views
            }
        }

        recyclerView.adapter = adapter
    }
})