FirebaseRecylerAdapater.java

public abstract class FirebaseRecyclerAdapter<T, VH extends RecyclerView.ViewHolder> extends RecyclerView.Adapter<VH> {

    Class<T> mModelClass;
    protected int mModelLayout;
    Class<VH> mViewHolderClass;
    FirebaseArray mSnapshots;

    public FirebaseRecyclerAdapter(Class<T> modelClass, int modelLayout, Class<VH> viewHolderClass, Query ref) {
        mModelClass = modelClass;
        mModelLayout = modelLayout;
        mViewHolderClass = viewHolderClass;
        mSnapshots = new FirebaseArray(ref);

        mSnapshots.setOnChangedListener(new FirebaseArray.OnChangedListener() {
            @Override
            public void onChanged(EventType type, int index, int oldIndex) {
                switch (type) {
                    case Added:
                        notifyItemInserted(index);
                        break;
                    case Changed:
                        notifyItemChanged(index);
                        break;
                    case Removed:
                        notifyItemRemoved(index);
                        break;
                    case Moved:
                        notifyItemMoved(oldIndex, index);
                        break;
                    default:
                        throw new IllegalStateException("Incomplete case statement");
                }
            }
        });
    }

    public FirebaseRecyclerAdapter(Class<T> modelClass, int modelLayout, Class<VH> viewHolderClass, Firebase ref) {
        this(modelClass, modelLayout, viewHolderClass, (Query) ref);
    }

    public void cleanup() {
        mSnapshots.cleanup();
    }

    @Override
    public int getItemCount() {
        return mSnapshots.getCount();
    }

    public T getItem(int position) {
        return parseSnapshot(mSnapshots.getItem(position));
    }

    protected T parseSnapshot(DataSnapshot snapshot) {
        return snapshot.getValue(mModelClass);
    }

    public Firebase getRef(int position) { return mSnapshots.getItem(position).getRef(); }

    @Override
    public long getItemId(int position) {
        // http://stackoverflow.com/questions/5100071/whats-the-purpose-of-item-ids-in-android-listview-adapter
        return mSnapshots.getItem(position).getKey().hashCode();
    }

    @Override
    public VH onCreateViewHolder(ViewGroup parent, int viewType) {
        ViewGroup view = (ViewGroup) LayoutInflater.from(parent.getContext()).inflate(mModelLayout, parent, false);
        try {
            Constructor<VH> constructor = mViewHolderClass.getConstructor(View.class);
            return constructor.newInstance(view);
        } catch (NoSuchMethodException e) {
            throw new RuntimeException(e);
        } catch (InvocationTargetException e) {
            throw new RuntimeException(e);
        } catch (InstantiationException e) {
            throw new RuntimeException(e);
        } catch (IllegalAccessException e) {
            throw new RuntimeException(e);
        }
    }
    @Override
    public void onBindViewHolder(VH viewHolder, int position) {
        T model = getItem(position);
        populateViewHolder(viewHolder, model, position);
    }

    abstract protected void populateViewHolder(VH viewHolder, T model, int position);
}