Pagination in endless recycler view with firebase

Question

I am working on Q/A app . I have successfully loaded questions from firebase . But I am not able to apply pagination from Firebase like database . And how to recognize that we h

Answer 1

To recognize that we have reached end of RecyclerView you can use this class EndlessRecyclerOnScrollListener.java

To load more next question, you should define one more field in Question class like number

public class Question {
    private int number; // it must unique and auto increase when you add new question
    ...
}

Then when you load questions from FireBase you can do like

public class MainActivity extends AppCompatActivity {
    private static final int TOTAL_ITEM_EACH_LOAD = 10;
    private DatabaseReference mDatabase;
    final List questionList = new ArrayList<>();

    private int currentPage = 0;

    private RecyclerView recyclerView;
    private RecyclerViewAdapter mAdapter; 

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        ...
        // init and set layout manager for your RecyclerView
        ...
        mAdapter = new RecyclerViewAdapter(questionList);
        recyclerView.setAdapter(mAdapter);
        recyclerView.setOnScrollListener(new EndlessRecyclerOnScrollListener(mLayoutManager) {
            @Override
            public void onLoadMore(int current_page) { // when we have reached end of RecyclerView this event fired
                loadMoreData();
            }
        });
        loadData(); // load data here for first time launch app
    }

    private void loadData() {
        // example
        // at first load : currentPage = 0 -> we startAt(0 * 10 = 0)
        // at second load (first loadmore) : currentPage = 1 -> we startAt(1 * 10 = 10)
        mDatabase.child("questions")
                .limitToFirst(TOTAL_ITEM_EACH_LOAD)
                .startAt(currentPage*TOTAL_ITEM_EACH_LOAD)
                .orderByChild("number")
                .addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(DataSnapshot dataSnapshot) {
                        if(!dataSnapshot.hasChildren()){
                            Toast.makeText(MainActivity.this, "No more questions", Toast.LENGTH_SHORT).show();
                            currentPage--;
                        }
                        for (DataSnapshot data : dataSnapshot.getChildren()) {
                            Question question = data.getValue(Question.class);
                            questionList.add(question);
                            mAdapter.notifyDataSetChanged();
                        }
                    }

                   @Override public void onCancelled(DatabaseError databaseError) {}});
    }

    private void loadMoreData(){
        currentPage++;
        loadData();
    }
}

Here is my DEMO project