how to store recyclerview data on onSaveInstanceState

问题

I want to save data from the API in the RecyclerView so that when rotating the screen is not reloaded

I think I can use onSaveInstanceState but still don't really understand how to use it

@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    final RecyclerView rvTVShow = view.findViewById(R.id.rv_shows);
    rvTVShow.setHasFixedSize(true);
    rvTVShow.setLayoutManager(new LinearLayoutManager(getActivity()));

    ApiInterface apiService =
            ApiClient.getClient().create(ApiInterface.class);
    Call<MovieResponse> call = apiService.getTVShow(API_KEY);
    call.enqueue(new Callback<MovieResponse>() {

        @Override
        public void onResponse(@NonNull Call<MovieResponse> call, @NonNull Response<MovieResponse> response) {
            final List<Movies> movies = Objects.requireNonNull(response.body()).getResults();

           TvShowAdapter tvShowAdapter = new TvShowAdapter(movies , R.layout.list_movies);
           rvTVShow.setAdapter(tvShowAdapter);

           ....
        }

回答1:

I will explain how savedInstanceState works while refactoring your code.

First: Create a global Movie object and an Adapter for it

  List<Movies> movies = new ArrayList();
  TvShowAdapter tvShowAdapter = null;

Re-initialize adapter under activity onCreate

  tvShowAdapter = new TvShowAdapter(movies , R.layout.list_movies);
       rvTVShow.setAdapter(tvShowAdapter);

Create a new method to handle movie data population

 public void populateRV(List<Movies> movies)
{
      this.movies = movies;
   //notify adapter about the new record
      tvShowAdapter.notifyDataSetChanged(); 
 }

Insert data to Movies object under your Response callback

  movies = Objects.requireNonNull(response.body()).getResults();
 populateRV(movies);

Everytime the orientation of an activity changes Android resets the states of all views by redrawing them. This causes non persistent data to be lost. But before redrawing views it calls the method onSavedInstanceState

Hence we can prevent state loss by saving the state of our views using the already defined onSavedInstanceState method provided by android.

Add the following block inside the overridden onSavedInstanceState method of your activity

 //this saves the data to a temporary storage
 savedInstanceState.putParcelableArrayList("movie_data", movies);
 //call super to commit your changes
 super.onSaveInstanceState(savedInstanceState);

Next is to recover the data after orientation change is completed

Add the following block in your activity onCreate and make sure it comes after initializing your adapter

 //...add the recyclerview adapter initialization block here before checking for saved data

 //Check for saved data
 if (savedInstanceState != null) {
 // Retrieve the data you saved
 movies = savedInstanceState.getParcelableArrayList("movie_data");

  //Call method to reload adapter record
 populateRV(movies);
 } else {
 //No data to retrieve
//Load your API values here.
 }

来源：https://stackoverflow.com/questions/57230396/how-to-store-recyclerview-data-on-onsaveinstancestate

标签

android

android-recyclerview

onsaveinstancestate