Cannot restore Scroll position

Question

Im stuck here 2 days. I am trying to restore scroll position after device rotation.

Im saving an arraylist in the onSaveInstance, adding the movies i have to it and trying to set the adapter.

If i switch shorting criteria and rotate the device, it scrolls up to the top and not retaining its position. Here's my code

public class MainActivity extends AppCompatActivity {

public static final String MOVIE_LIST = "instanceMovieList";
public static final String RECYCLER_VIEW_STATE_KEY = "RECYCLER_VIEW_STATE_KEY";
private static final String LOG_TAG = MainActivity.class.getSimpleName();
Context mContext;
Toolbar mToolBar;
@BindView(R.id.prefSpinnner)
Spinner prefSpinner;
@BindView(R.id.noDataTv)
TextView noDataTv;
@BindView(R.id.rv_movies)
RecyclerView mMoviesRV;
private AppDatabase mDb;
private String userOption = "Most Popular";
private ArrayList<Movie> mMoviesList = new ArrayList<>();
private MovieRecycleViewAdapter movieRecycleViewAdapter;
private RecyclerView.LayoutManager mLayoutManager;
private Parcelable mListState;

@Override
protected void onSaveInstanceState(Bundle outState) {
    if (mMoviesList != null) {
        outState.putParcelableArrayList(MOVIE_LIST, mMoviesList);
        mListState = mLayoutManager.onSaveInstanceState();
        outState.putParcelable(RECYCLER_VIEW_STATE_KEY, mListState);
    }
    super.onSaveInstanceState(outState);
}


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ButterKnife.bind(this);


    GridLayoutManager gridLayoutManager = new GridLayoutManager(this, 2);
    mMoviesRV.setLayoutManager(gridLayoutManager);
    mMoviesRV.setHasFixedSize(true);
    movieRecycleViewAdapter = new MovieRecycleViewAdapter(MainActivity.this, mMoviesList);
    mMoviesRV.setAdapter(movieRecycleViewAdapter);

    mLayoutManager = mMoviesRV.getLayoutManager();

    if (savedInstanceState != null && savedInstanceState.containsKey(MOVIE_LIST)) {
        ArrayList<Movie> savedMovieList = savedInstanceState.getParcelableArrayList(MOVIE_LIST);
        Log.d(LOG_TAG, "getting movies from instance ");
        mMoviesList.addAll(savedMovieList);
        movieRecycleViewAdapter = new MovieRecycleViewAdapter(MainActivity.this, mMoviesList);
        mMoviesRV.setAdapter(movieRecycleViewAdapter);
    }

    mToolBar = findViewById(R.id.toolbar);

    mToolBar.setTitle(getResources().getString(R.string.app_name));

    ArrayAdapter<String> spinAdapter = new ArrayAdapter<String>(MainActivity.this, R.layout.pref_spinner_item_list, getResources().getStringArray(R.array.userPrefs));
    spinAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    prefSpinner.setAdapter(spinAdapter);

    prefSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
            userOption = prefSpinner.getSelectedItem().toString();

            if (userOption.contentEquals("Most Popular") || userOption.contentEquals("Highest Rated")) {
                PopulateMoviesTask newTask = new PopulateMoviesTask();
                newTask.execute();


            } else {
                setUpViewModel();
            }
        }

        @Override
        public void onNothingSelected(AdapterView<?> adapterView) {
            PopulateMoviesTask newTask = new PopulateMoviesTask();
            newTask.execute();
        }
    });
    mDb = AppDatabase.getInstance(getApplicationContext());

}

private void setUpViewModel() {
    MainViewModel viewModel = ViewModelProviders.of(this).get(MainViewModel.class);
    viewModel.getMovies().observe(this, new Observer<List<Movie>>() {
        @Override
        public void onChanged(@Nullable List<Movie> movies) {
            Log.d(LOG_TAG, "updating list of movies from livedata in viewmodel");
            movieRecycleViewAdapter.setMovies(movies);
        }
    });
}

@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);

    if (savedInstanceState != null) {
        mMoviesList = savedInstanceState.getParcelableArrayList(MOVIE_LIST);
        mListState = savedInstanceState.getParcelable(RECYCLER_VIEW_STATE_KEY);
    }
}

@Override
protected void onResume() {
    super.onResume();
    if (mListState != null) {
        mLayoutManager.onRestoreInstanceState(mListState);
    }
}

private class PopulateMoviesTask extends AsyncTask<URL, Void, String> {

    @Override
    protected String doInBackground(URL... urls) {
        URL searchMovieObjectUrl = NetworkUtils.createUrl(userOption);
        String jsonString = "";

        try {
            jsonString = NetworkUtils.makeHttpRequest(searchMovieObjectUrl);
        } catch (IOException e) {
            Log.e("Main Activity", "Problem making the HTTP request.", e);
        }
        return jsonString;
    }

    @Override
    protected void onPostExecute(String jsonString) {
        if (jsonString == null) {
            mMoviesRV.setVisibility(View.GONE);
            noDataTv.setVisibility(View.VISIBLE);
        } else {
            mMoviesRV.setVisibility(View.VISIBLE);
            noDataTv.setVisibility(View.GONE);
            mMoviesList = JsonUtils.extractFeatureFromJson(jsonString);
        }
        movieRecycleViewAdapter = new MovieRecycleViewAdapter(MainActivity.this, mMoviesList);
        mMoviesRV.setAdapter(movieRecycleViewAdapter);
    }
}

}

score 0 · Answer 1 · answered Nov 28 '18 at 11:35

0

Use this

private Parcelable recyclerViewState;// global

onResume

 @Override
public void onResume() {
    super.onResume();
    mMoviesRV.getLayoutManager().onRestoreInstanceState(recyclerViewState);
}

onPasue

  @Override
public void onPause() {
    super.onPause();
    recyclerViewState= mMoviesRV.getLayoutManager().onSaveInstanceState();

}

answered Nov 28 '18 at 11:35

mehul chauhan

1,661
9
19

I did. Still the same. Do you believe it has anything to do with my postExecute? – Pointyhat Nov 28 '18 at 11:38

score 0 · Answer 2 · answered Nov 28 '18 at 17:34

Since i found out what was going on, i think i should post an answer.

@Override protected void onSaveInstanceState(Bundle outState) {
if (mMoviesList != null) {
    outState.putParcelableArrayList(MOVIE_LIST, mMoviesList);
    mListState = mLayoutManager.onSaveInstanceState();
    outState.putParcelable(RECYCLER_VIEW_STATE_KEY, mListState);
}
super.onSaveInstanceState(outState);

}

is enough to save the moviesList through lifecycle and then retrieve it

if (savedInstanceState != null && savedInstanceState.containsKey(MOVIE_LIST)) {
        mMoviesList = savedInstanceState.getParcelableArrayList(MOVIE_LIST);

This answers the original question

But the problem was in my adapter and WHEN i was initializing it. The adapter should only be initialized in onCreate (in my case at least) and then notify it if the Arraylist data changed more info here.

Cannot restore Scroll position

2 Answers2