Tukukkk

I have a Fragment that contains a Recylcerview. This RecyclerView is populated using the Firebase FirestoreUI.

Below is the code for my RecyclerView, which I call in .onStart() to listen to changes:

@Override

    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {

        super.onViewCreated(view, savedInstanceState);

        if (savedInstanceState != null) {

            mRecyclerViewState = savedInstanceState.getParcelable(RECYCLERVIEW_STATE);

        }

        mRecyclerview = (RecyclerView) view.findViewById(R.id.list);

        mPollHolderArray = new ArrayList<>();

        mRecyclerview.getItemAnimator().setChangeDuration(0);





        mLayoutManager = new LinearLayoutManager(getContext());

        mLayoutManager.setOrientation(LinearLayoutManager.VERTICAL);

        //TODO: Detertmine if necessary since ordering is now different in Firebase

        mLayoutManager.setReverseLayout(true);

        mLayoutManager.setStackFromEnd(true);



        mFloatingActionAdd = (FloatingActionButton) getActivity().findViewById(R.id.myFAB);

        mFloatingActionAdd.setOnClickListener(new View.OnClickListener() {

            @Override

            public void onClick(View v) {

                Intent I = new Intent(getActivity().getApplicationContext(), CreateActivity.class);

                startActivity(I);

            }

        });





        mRecyclerview.setLayoutManager(mLayoutManager);



        if (mRecyclerViewState != null){

            mLayoutManager.onRestoreInstanceState(mRecyclerViewState);

        }





        if (mFirestoreAdaper == null) {

            Query queryStore = FirebaseFirestore.getInstance()

                    .collection(POLLS_LABEL)

                    .orderBy("timestamp", Query.Direction.ASCENDING);

            //Cloud Firestore does not have any ordering; must implement a timestampe to order sequentially



            FirestoreRecyclerOptions<Poll> storeOptions = new FirestoreRecyclerOptions.Builder<Poll>()

                    .setQuery(queryStore, Poll.class)

                    .build();

            mFirestoreAdaper = new FirestoreRecyclerAdapter<Poll, PollHolder>(storeOptions) {

                @Override

                protected void onBindViewHolder(@NonNull final PollHolder holder, final int position, @NonNull Poll model) {

                    holder.mPollQuestion.setText(model.getQuestion());

                    String voteCount = String.valueOf(model.getVote_count());

                    //TODO: Investigate formatting of vote count for thousands

                    holder.mVoteCount.setText(voteCount);

                    Picasso.get()

                            .load(model.getImage_URL())

                            .fit()

                            .into(holder.mPollImage);

                    holder.mView.setOnClickListener(new View.OnClickListener() {

                        @Override

                        public void onClick(View view) {

                            Intent toClickedPoll = new Intent(getActivity(), PollHostActivity.class);

                            String recyclerPosition = getSnapshots().getSnapshot(position).getId();

                            Log.v("Firestore ID", recyclerPosition);

                            toClickedPoll.putExtra("POLL_ID", recyclerPosition);

                            startActivity(toClickedPoll);



                        }

                    });

                }





                @Override

                public PollHolder onCreateViewHolder(ViewGroup parent, int viewType) {

                    View v = LayoutInflater.from(parent.getContext())

                            .inflate(R.layout.latest_item, parent, false);

                    return new PollHolder(v);

                }





            };

            mRecyclerview.setAdapter(mFirestoreAdaper);

        }

    }

When I navigate to another Fragment (onClick of the RecyclerView) and then back to the Fragment containing this RecyclerView, I expect to be able to maintain the position that was clicked. However, this is not occurring. Below is the code I have tried to save the state, it is simply reverting back to the top item of the RecyclerView:

    @Override

    public void onSaveInstanceState(@NonNull Bundle outState) {

    super.onSaveInstanceState(outState);

    mRecyclerViewState = mLayoutManager.onSaveInstanceState();

    outState.putParcelable(RECYCLERVIEW_STATE, mRecyclerViewState);



}

EDIT: The original Fragment is part of a ViewPager (I am testing it right now on the NewFragment):

    public class SectionPagerAdapter extends FragmentPagerAdapter {



    public SectionPagerAdapter(FragmentManager fm) {

        super(fm);

    }



    @Override

    public Fragment getItem(int position) {

        switch (position) {

            case 0:

                return new TrendingFragment();

            case 1:

                return new FollowingFragment();

            case 2:

                return new NewFragment();

            default:

                return new TrendingFragment();

        }

    }

That's because you're setting new adapter in onStart, and that happens whenever you resume the fragment, either from previous screen or background.

You don't need all these logics to help to remember the position, you just have to initialise and set your adapter in the right place within the lifecycle.

In your fragment, set your adapter in onViewCreated instead of onStart:

@Override public void onViewCreated(View view, Bundle savedInstanceState) {

    super.onViewCreated(view, savedInstanceState);

    mRecyclerview = view.findViewById(...);

    if (mAdapter == null) {

        mAdapter = new FirestoreRecyclerAdapter(...)

        mRecyclerView.setAdapter(mAdapter);

        mAdapter.startListening();

    }

}



@Override public void onDestroyView() {

    super.onDestroyView();

    mAdapter.stopListening();

}

And remove all of your logics of saving and restoring position (onSaveInstanceState, scrollToPosition, onRestoreInstanceState), you don't need them!