how to paginate data in viewModel with recycler view in fragment using firestore

Question

I am trying to paginate data from fire Store into recycler view with limit of 10 documents I am using staggered grid layout recycler view and view pager, I am holding data in view model class and observing it from two different fragments -- one containing view pager and another containing grid recycler view, how can implement Pagination? I know how to implement it without view model but I need the idea to implement it with view model !

I just want rough idea of steps to implement this not the code.

Answer 1

You have to make local pagination from firebase data array. then set limit and get data from the array.

 mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener()
{
   @Override
   public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
      if (dy > 0) //check for scroll down
      {
        visibleItemCount = mLayoutManager.getChildCount();
        totalItemCount = mLayoutManager.getItemCount();
        pastVisibleItems = mLayoutManager.findFirstVisibleItemPosition();

        if (loading) {
            if ((visibleItemCount + pastVisibleItems) >= totalItemCount) {
                loading = false;
                if (adapter.countOfShowing < adapter.allChallenges.size()) {
                 //Last data.....
                    adapter.notifyDataSetChanged();
                }
                loading = true;
                //fetch new data
            }
          }
        }
      }
  });