How to refresh data in a RecyclerView from a PagedListAdapter?

Question

Using the following lines of code, I can to display data from a backend server in a RecyclerView using PagedListAdapter.

movieViewModel = ViewModelProviders.of(this).get(MovieViewModel.class);
MovieAdapter adapter = new MovieAdapter(this);
movieViewModel.moviePagedList.observe(this, adapter::submitList);
recyclerView.setAdapter(adapter);

I created this method:

private void movieSearch(String searchText) {
    globalSearch = searchText;
    movieViewModel.replaceSubscription(this);
    movieViewModel = ViewModelProviders.of(this).get(MovieViewModel.class);
    MovieAdapter adapter = new MovieAdapter(this);
    movieViewModel.moviePagedList.observe(this, adapter::submitList);
    recyclerView.setAdapter(adapter);
}

Which is called from inside onQueryTextChange() to display the results of the search but for some reasons the data in my RecyclerView is not refreshed.

This is also my MovieViewModel class:

public class MovieViewModel extends ViewModel {
    LiveData<PagedList<ApiResponse.Movie>> moviePagedList;

    public MovieViewModel() {
        MovieDataSourceFactory movieDataSourceFactory = new MovieDataSourceFactory(search);
        PagedList.Config config = new PagedList.Config.Builder().setEnablePlaceholders(false).setPageSize(20).build();
        moviePagedList = new LivePagedListBuilder<>(movieDataSourceFactory, config).build();
    }

    void replaceSubscription(LifecycleOwner lifecycleOwner) {
        moviePagedList.removeObservers(lifecycleOwner);
    }
}

I everytime I search something, I need to get freash data. How to solve this?

Answer 1

PagedListAdapter is a subclass of android.support.v7.widget.RecyclerView.Adapter so a call to notifyDataSetChanged() will do.

Answer 2

With this answer I will show you how I did filtering of items in my Adapter. Not answering your question directly, but rather giving you another solution.

First of, I have a EditText in my ToolBar called m_app_bar_title_txt, In my Activity I call the following:

//I'm using TextWatcher to see when text changes
m_app_bar_title_txt.addTextChangedListener(new TextWatcher() {

    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
    }

    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
    }

    @Override
    public void afterTextChanged(Editable s) {
        //If the text changes I call the following method
        //Passing the text to the metod
        filter(s.toString());
    }
});

private void filter(String s) {
    ArrayList<ScoresData> aData = new ArrayList<>();
    for (ScoresData mData : data){
        if (mData.textPlayerName.toLowerCase().contains(s.toLowerCase())){
            aData.add(mData);
        }
    }
    //this method is in my RecyclerView.Adapter class
    //I will provide this below
    mAdapter.filterList(aData);

}

mAdapter.filterList(aData); passes the filtered ArrayList to the following method inside my RecyclerView.Adapter:

public void filterList(ArrayList<ScoresData> filteredList){
    //Changing the original ArrayList -> data to filteredList
    //Then notifying that the list has changed
    data = filteredList;
    notifyDataSetChanged();
}

If you where wondering what ScoresData looks like....

public class ScoresData {
    public String mImage;
    public String textPlayerName;
    public String textPos;
    public String textTotalScore;
    public String textPlayed;
    public String textRounds;
}

I hope this helps..

Answer 3

This is written in the documentation of DataSource

A PagedList / DataSource pair are a snapshot of the data set. A new pair of PagedList / DataSource must be created if an update occurs, such as a reorder, insert, delete, or content update occurs. A DataSource must detect that it cannot continue loading its snapshot (for instance, when Database query notices a table being invalidated), and call invalidate(). Then a new PagedList / DataSource pair would be created to load data from the new state of the Database query.

I think this is the answer.

Answer 4

This problem can be solved by calling

movieViewModel.moviePagedList.dataSource.invalidate()

in your activity/fragment.

Answer 5

call adapter.refresh()

swiperefresh.setOnRefreshListener {
  movieListAdapter.refresh()
  swiperefresh.isRefreshing = false
}

note movieListAdapter should extend PagingDataAdapter