Find nearby users in Firebase Realtime DB

Question

I would like to know how can I get all the users that are in a radius of the current user's location. So far I am able to get everyone's coordinates. What I am unable to do is get the users that are nearby fast without having to search the whole database (I am using Firebase Realtime DB). Is there an algorithm that can help with that?

Answer 1

The fastest and best way I found was using GeoFIre. In your onCreate() method add the following lines

DatabaseReference ref = FirebaseDatabase.getInstance().getReference("path/to/geofire");
GeoFire geoFire = new GeoFire(ref);

Provided we have our location, then we can simply use GeoQueries in a method in order to get the result we want.

// creates a new query around [latitude, longitude] with a radius of 10.00 kilometers
GeoQuery geoQuery = geoFire.queryAtLocation(new GeoLocation(Double.parseDouble(latitude), Double.parseDouble(longitude)), 10.00);
geoQuery.addGeoQueryEventListener(new GeoQueryEventListener() {
            @Override
            public void onKeyEntered(String key, GeoLocation location) {
                    Log.d("KEY", "KEY IS: " + key);
                    if (!key.equals(currentUserID) && !nearbyList.contains(key)) {
                        Log.d("KEY FOUND", "Key " + key + " entered the search area at" + location.latitude + "," + location.longitude);

                        usersRef.child(key).addListenerForSingleValueEvent(new ValueEventListener() {
                            @Override
                            public void onDataChange(@NonNull DataSnapshot snapshot) {
                               /* Get your data from Firebase here */
                            }

                            @Override
                            public void onCancelled(@NonNull DatabaseError error) {

                            }
                        });
                    }
                }
            }

            @Override
            public void onKeyExited(String key) {
                /* When someone exits the radius */
            }

            @Override
            public void onKeyMoved(String key, GeoLocation location) {

            }

            @Override
            public void onGeoQueryReady() {

            }

            @Override
            public void onGeoQueryError(DatabaseError error) {

            }
        });