旋转时固定滚动位置

Question

我想在旋转手机时保持固定的滚动位置。这是我的代码。

public class MainActivityFragment extends Fragment {
    private static final String TAG = MainActivityFragment.class.getSimpleName();
    private static final String ARRAY_LIST = "list_view";
    private static final String LAYOUT_STATE = "MainActivityFragment.recycler.layout";
    ArrayList<Movie> movies;
    RecyclerView recyclerView;
    private MovieAdapter movieAdapter;
    private SwipeRefreshLayout swipeRefreshLayout;

    public MainActivityFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment

        View rootView = inflater.inflate(R.layout.fragment_main_activity, container, false);

        if(savedInstanceState == null) {

            MovieDataService movieDataService = RetrofitInstance.getService();

            Call<MovieDBResponse> call = movieDataService.getPopularMovies(BuildConfig.MOVIESDB_API_KEY);

            call.enqueue(new Callback<MovieDBResponse>() {
                @Override
                public void onResponse(Call<MovieDBResponse> call, Response<MovieDBResponse> response) {
                    MovieDBResponse movieDBResponse = response.body();
                    Log.i(TAG, "inside retrofit");
                    if (movieDBResponse != null) {


                        movies = (ArrayList<Movie>) movieDBResponse.getResults();

                        recyclerView = rootView.findViewById(R.id.rvMovies);

                        movieAdapter = new MovieAdapter(getActivity(), movies);

                        swipeRefreshLayout = rootView.findViewById(R.id.swipe_layout);
                        swipeRefreshLayout.setColorSchemeResources(R.color.colorPrimary);
                        //swipeRefreshLayout.setOnRefreshListener(()-> getPopularMovies());

                        if (getActivity().getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT) {

                            recyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 2));

                        } else {
                            recyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 4));
                        }

                        recyclerView.setItemAnimator(new DefaultItemAnimator());
                        recyclerView.setAdapter(movieAdapter);
                        movieAdapter.notifyDataSetChanged();

                    }


                }

                @Override
                public void onFailure(Call<MovieDBResponse> call, Throwable t) {
                }
            });

        }else{
            movies = savedInstanceState.getParcelableArrayList(ARRAY_LIST);

            recyclerView = rootView.findViewById(R.id.rvMovies);

            movieAdapter = new MovieAdapter(getActivity(), movies);

            swipeRefreshLayout = rootView.findViewById(R.id.swipe_layout);
            swipeRefreshLayout.setColorSchemeResources(R.color.colorPrimary);
            //swipeRefreshLayout.setOnRefreshListener(()-> getPopularMovies());

            if (getActivity().getResources().getConfiguration().orientation == Configuration.ORIENTATION_PORTRAIT) {

                recyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 2));

            } else {
                recyclerView.setLayoutManager(new GridLayoutManager(getActivity(), 4));
            }

            recyclerView.setItemAnimator(new DefaultItemAnimator());
            recyclerView.setAdapter(movieAdapter);
            movieAdapter.notifyDataSetChanged();
        }

    return rootView;
    }

    @Override
    public void onSaveInstanceState(@NonNull Bundle outState) {
        super.onSaveInstanceState(outState);
        outState.putParcelableArrayList(ARRAY_LIST,movies);
        outState.putParcelable(LAYOUT_STATE, recyclerView.getLayoutManager().onSaveInstanceState());

    }

    @Override
    public void onViewStateRestored(@Nullable Bundle savedInstanceState) {
        super.onViewStateRestored(savedInstanceState);
        if(savedInstanceState != null)
        {
            Parcelable savedRecyclerLayoutState = savedInstanceState.getParcelable(LAYOUT_STATE);
            recyclerView.getLayoutManager().onRestoreInstanceState(savedRecyclerLayoutState);
        }
    }
}

我正在使用onSaveInstanceState和onViewStateRestored方法，但是当我旋转手机时，固定的滚动位置不起作用。如何解决？

谢谢

Theo。