How to paginate Firestore with Android?

Question

I read Firestore documentation and all articles on internet(stackoverflow) about Firestore pagination but no luck. I tried to implement the exact code in docs, but nothing h

Answer 1

You can also use FirestorePagingAdapter provided by Firebase-UI-Firestore

You need to install this dependency

 implementation 'com.firebaseui:firebase-ui-firestore:latest_version_here'

Solution

Step 1: Create a global Firestore paging adapter variable and pass the Model class and ViewHolder, and also the Model variable.

private FirestorePagingAdapter adapter;
private Model model;

Step 2: Create a firebase query

Query query = db.collection("cities")
    .orderBy("population");

Step 3: Let's build the pagedlist config. Here you will pass how much data to be queried in each page;

PagedList.Config config = new PagedList.Config.Builder()
                .setEnablePlaceholders(false)
                .setPrefetchDistance(10)
                .setPageSize(15)
                .build();

Step 4: After setting the config, let's now build the Firestore paging options where you will pass the query and config.

 FirestorePagingOptions options = new FirestorePagingOptions.Builder()
                .setLifecycleOwner(this)
                .setQuery(query, config, snapshot -> {
                    model = snapshot.toObject(Model.class);
                    return model;
                })
                .build();

Step: 5 Now let's pass the data to the Recylerview

 adapter = new FirestorePagingAdapter(options) {
            @Override
            protected void onBindViewHolder(@NonNull ModelViewHolder holder, int position, @NonNull Model model) {
                holder.bindTO(model);
            }

            @NonNull
            @Override
            public ModelViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
                View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.layout_model, parent, false);
                return new ModelViewHolder(view);
            }

            @Override
            protected void onError(@NonNull Exception e) {
                super.onError(e);
                     //logic here
            }

            @Override
            protected void onLoadingStateChanged(@NonNull LoadingState state) {
                switch (state) {
                    case LOADING_INITIAL:
                        break;

                    case LOADING_MORE:
                        break;

                    case LOADED:
                        notifyDataSetChanged();
                        break;

                    case ERROR:
                        Toast.makeText(requireActivity(), "Error", Toast.LENGTH_SHORT).show();
                         //logic here
                        break;

                    case FINISHED:
                        //logic here
                        break;
                }
            }
        };
        productRecycler.setAdapter(adapter);
        adapter.notifyDataSetChanged();
    }

Happy Coding!