Retrieving data from Firebase Realtime Database in Android

Question

I\'m new to Firebase and NoSQL. I have an Android Demo, with a City Autocomplete Text Field in which I want to populate the cities I have from my Firebase DB, while typing.<

Answer 1

@NicholasChen has identified the problem. But here's the way you'd implement using the 3.x SDK:

DatabaseReference cities = databaseRef.child("cities")
Query citiesQuery = cities.orderByKey().startAt(input).endAt(input+"\uf8ff");
citiesQuery.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        List cities = new ArrayList();
        for (DataSnapshot postSnapshot: dataSnapshot.getChildren()) {
            cities.add(postSnapshot.getValue().toString());
        }

By starting at the user input and ending at the last string that starts with the user input, you get all matching items

For relatively short lists of items Ryan's approach will also work fine. But the above Firebase query will filter server-side.

Update

I just ran this code:

    DatabaseReference databaseRef = FirebaseDatabase.getInstance().getReference("39714936");

    String input = "G";

    DatabaseReference cities = databaseRef.child("cities");
    Query citiesQuery = cities.orderByKey().startAt(input).endAt(input + "\uf8ff");
    citiesQuery.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            List cities = new ArrayList();

            for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                cities.add(postSnapshot.getValue().toString());
            }
            System.out.println(cities);
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

And it printed:

true

true

So clearly matches two cities.

Feel free to test against my database: https://stackoverflow.firebaseio.com/39714936