var mPeople: ArrayList<Person> = ArrayList()
var mAdapter: PersonFirestoredapter = PersonFirestoredapter(this, mPeople)

var mRecyclerView: RecyclerView = findViewById(R.id.rv)
mRecyclerView.setHasFixedSize(true)
mRecyclerView.layoutManager = LinearLayoutManager(this)

var db: FirebaseFirestore = FirebaseFirestore.getInstance()