Condition to notifyDataSetChanged to adapter when onGeoQueryReady

Question

a little question about the correct approach when dealing with geoQueries and adapters.

I have a list of users keys in a GeoQuery database (with coordinates obviously), and I would like to display them in a ListView when they enter in a certain range.

Here's some code.

    usersGeoQuery.addGeoQueryEventListener(new GeoQueryEventListener() {

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

            firebaseDatabase.getReference("users").child(key).addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                    User user = dataSnapshot.getValue(User.class);
                    users.add(user);
                    // if ( ??? ) 
                    mAdapter.notifyDataSetChanged();
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });
        }

        @Override
        public void onKeyExited(String key) {
            for(Iterator<User> it = users.iterator(); it.hasNext();){
                User user = it.next();
                if(user.id == key){
                    it.remove();
                }
            }
            // if ( ??? )
            mAdapter.notifyDataSetChanged();
        }

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

        @Override
        public void onGeoQueryReady() { 
            // this actually triggers before firebase listeners
        }

        @Override
        public void onGeoQueryError(DatabaseError error) {
        }
    });

Actually, this works, but, of course, it notifies changes to the adapter everytime a entry it's added to the list. So it's not good for performance.

Any suggestion for a smart approach about this?

Thanks!

Answer 1

The typical approach would be to keep a count of pending items. So every time you get a new key, you increment the counter. Every time you get the corresponding data, you decrement. Once the counter is 0 and onGeoQueryReady fired, you know you've gotten all the initial items.