I'm learning Android MVP architecture given here. Based on the example I created my own simple app that just displays list with recyclerview with pull to refresh functionality.
When list is pulled I want first to clear the recyclerview and then reload the data again from the repository (with fake latency delay). But, when I clear the data inside RecyclerViewAdpater, all data inside repository are also being cleared and there is nothing to show. I just can't understand the reason.
Here's my activity that creates both Presenter and View (that is Fragment):
protected void onCreate(Bundle savedInstanceState) { mainFragment = MainFragment.newInstance(); FragmentTransaction transaction = getSupportFragmentManager().beginTransaction(); transaction.add(R.id.contentFrame, mainFragment); transaction.commit(); new MainPresenter(new MainDataRepository(), mainFragment); } Here's my Fragment (MainFragment) - ATTENTION: updateList(null) - This is where it clears all data, including inside Repository:
public MainFragment() { } public static MainFragment newInstance() { return new MainFragment(); } @Nullable @Override public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { //.... swipeRefreshLayout.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() { @Override public void onRefresh() { recyclerAdapter.updateList(null); // **This is where it clears all data, including inside Repository** Handler handler = new Handler(); handler.postDelayed(new Runnable() { @Override public void run() { mPresenter.loadList(); // to reload the list } }, 1500); } }); //... } @Override public void onResume() { super.onResume(); Handler handler = new Handler(); handler.postDelayed(new Runnable() { @Override public void run() { mPresenter.loadList(); } }, 3000); } @Override public void setPresenter(MainContractor.Presenter presenter) { mPresenter = presenter; } @Override public void showList(List<String> mainDataList) { if(recyclerAdapter == null) { recyclerAdapter = new RecyclerAdapter(mainDataList); recyclerView.setLayoutManager(new LinearLayoutManager(getActivity())); recyclerView.setAdapter(recyclerAdapter); }else{ recyclerAdapter.updateList(mainDataList); } } Here's my presenter (MainPresenter):
public MainPresenter(MainDataRepository mainDataRepository, MainContractor.View view){ mMainDataRepository = mainDataRepository; mMainContractorView = view; view.setPresenter(this); } @Override public void loadList() { ArrayList<String> strings = mMainDataRepository.getList(); mMainContractorView.showList(strings); } Here's my repository (MainDataRepository):
private ArrayList<String> repositoryList; public MainDataRepository() { createList(); } private void createList() { if(repositoryList == null){ repositoryList = new ArrayList<>(); } for (int i = 1; i <= 10; i++) { repositoryList.add("Item " + i); } } public ArrayList<String> getList(){ return repositoryList; } And the last one, This is how I am updating recyclerview inside RecyclerAdapter:
public class RecyclerAdapter extends RecyclerView.Adapter<RecyclerAdapter.MyViewHolder> { private List<String> stringsList; public RecyclerAdapter(List<String> stringsList) { this.stringsList = stringsList; } public void updateList(List<String> newStrings){ if(newStrings != null){ stringsList = newStrings; }else{ stringsList.clear(); } notifyDataSetChanged(); } //.... } Why updateList mehod inside RecyclerAdapter also clears the data inside repository that is ArrayList<String> repositoryList?
