Styjun

I want to feed the recyclerview with a list of elements and livedata. I used data binding adapter and when I want to send data to adapter the list return null from livedata. the whole code are below.
thanks

I debugged the code and I saw when the data came from the AppDbHelper.java to HomeViewmodel.java and set to the live data the bindingadapter didn't change. thus, although the livedata is not null, the arraylist at databinding adapter(heartRateResultsModels) is null and made the app crashed.

1.fragment_home.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:app="http://schemas.android.com/apk/res-auto"
 xmlns:tools="http://schemas.android.com/tools">

 <data>

 <variable
 name="viewModel"
 type="ir.basamadazmanovin.heartrate.ui.main.home.HomeViewModel" />
 </data>

 <androidx.swiperefreshlayout.widget.SwipeRefreshLayout
 android:id="@+id/swipe_refresh_layout"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 app:refreshing="@viewModel.isLoading">

 <FrameLayout
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 tools:context=".ui.main.home.HomeFragment">

 <androidx.recyclerview.widget.RecyclerView
 android:id="@+id/fragment_home_recyclerView"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 app:adapter="@viewModel.heartRateResultsLiveData"
 tools:listitem="@layout/row_fragment_home" />


 </FrameLayout>
 </androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
</layout>

2.BaseFragment.java

public abstract class BaseFragment<T extends ViewDataBinding, V extends BaseViewModel> extends Fragment 

 protected FragmentNavigation mFragmentNavigation;
 private BaseActivity mActivity;
 private View mRootView;
 private T mViewDataBinding;
 private V mViewModel;

 public abstract int getBindingVariable();

 public abstract
 @LayoutRes
 int getLayoutId();

 public abstract V getViewModel();

 @Override
 public void onAttach(Context context) 
 super.onAttach(context);
 if (context instanceof BaseActivity) 
 BaseActivity activity = (BaseActivity) context;
 this.mActivity = activity;
 activity.onFragmentAttached();
 
 if (context instanceof FragmentNavigation) 
 mFragmentNavigation = (FragmentNavigation) context;
 else 
 throw new RuntimeException(context.toString()
 + " must implement OnFragmentInteractionListener");
 
 

 @Override
 public void onCreate(@Nullable Bundle savedInstanceState) 
 performDependencyInjection();
 super.onCreate(savedInstanceState);
 mViewModel = getViewModel();
 setHasOptionsMenu(false);
 

 @Override
 public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) 
 mViewDataBinding = DataBindingUtil.inflate(inflater, getLayoutId(), container, false);
 mRootView = mViewDataBinding.getRoot();
 return mRootView;
 

 public BaseActivity getBaseActivity() 
 return mActivity;
 

 public T getViewDataBinding() 
 return mViewDataBinding;
 

 public void hideKeyboard() 
 if (mActivity != null) 
 mActivity.hideKeyboard();
 
 

 public boolean isNetworkConnected() 
 return mActivity != null && mActivity.isNetworkConnected();
 

 public void openActivityOnTokenExpire() 
 if (mActivity != null) 
 mActivity.openActivityOnTokenExpire();
 
 

 private void performDependencyInjection() 
 AndroidSupportInjection.inject(this);
 

 public interface Callback 

 void onFragmentAttached();

 void onFragmentDetached(String tag);
 

3.HomeFragment.java

public class HomeFragment extends BaseFragment<FragmentHomeBinding,HomeViewModel> implements HomeNavigator 

 FragmentHomeBinding mFragmentHomeBinding;
 @Inject
 LinearLayoutManager mLayoutManager;
 @Inject
 HeartRateResultsAdapter mAdapter;
 @Inject
 ViewModelProviderFactory factory;




 private HomeViewModel mHomeViewModel;

 public static HomeFragment newInstance() 
 return new HomeFragment();
 

 @Override
 public int getBindingVariable() 
 return BR.viewModel;
 

 @Override
 public int getLayoutId() 
 return R.layout.fragment_home;
 

 @Override
 public HomeViewModel getViewModel() 
 mHomeViewModel = ViewModelProviders.of(this, factory).get(HomeViewModel.class);
 return null;
 

 @Override
 public void onCreate(@Nullable Bundle savedInstanceState) 
 super.onCreate(savedInstanceState);
 mHomeViewModel.setNavigator(this);

 

 @Override
 public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) 
 super.onViewCreated(view, savedInstanceState);
 mFragmentHomeBinding = getViewDataBinding();
 setUp();
 

 private void setUp() 
 mLayoutManager.setOrientation(RecyclerView.VERTICAL);
 mFragmentHomeBinding.fragmentHomeRecyclerView.setLayoutManager(mLayoutManager);
 mFragmentHomeBinding.fragmentHomeRecyclerView.setItemAnimator(new DefaultItemAnimator());
 mFragmentHomeBinding.fragmentHomeRecyclerView.setAdapter(mAdapter);
 

 @Override
 public void handleError(Throwable throwable) 

 

4.BaseViewModel.java

public class BaseViewModel<N> extends ViewModel 
 private final DataManager mDataManager;

 private final ObservableBoolean mIsLoading = new ObservableBoolean(false);

 private final SchedulerProvider mSchedulerProvider;

 private CompositeDisposable mCompositeDisposable;

 private WeakReference<N> mNavigator;

 public BaseViewModel(DataManager dataManager,
 SchedulerProvider schedulerProvider) 
 this.mDataManager = dataManager;
 this.mSchedulerProvider = schedulerProvider;
 this.mCompositeDisposable = new CompositeDisposable();
 

 @Override
 protected void onCleared() 
 mCompositeDisposable.dispose();
 super.onCleared();
 

 public CompositeDisposable getCompositeDisposable() 
 return mCompositeDisposable;
 

 public DataManager getDataManager() 
 return mDataManager;
 

 public ObservableBoolean getIsLoading() 
 return mIsLoading;
 

 public void setIsLoading(boolean isLoading) 
 mIsLoading.set(isLoading);
 

 public N getNavigator() 
 return mNavigator.get();
 

 public void setNavigator(N navigator) 
 this.mNavigator = new WeakReference<>(navigator);
 

 public SchedulerProvider getSchedulerProvider() 
 return mSchedulerProvider;
 

5.HomeViewModel.java

public class HomeViewModel extends BaseViewModel<HomeNavigator> 
 private MutableLiveData<ArrayList<HeartRateResultsModel>> heartRateResultsLiveData;

 public HomeViewModel(DataManager dataManager, SchedulerProvider schedulerProvider) 
 super(dataManager, schedulerProvider);
 heartRateResultsLiveData = new MutableLiveData<>();
 fetchRepos();
 
 public void fetchRepos() 
 setIsLoading(true);
 getCompositeDisposable().add(getDataManager()
 .getHeartRateResults()
 .subscribeOn(getSchedulerProvider().io())
 .observeOn(getSchedulerProvider().ui())
 .subscribe(heartRateResultsModels -> 
 heartRateResultsLiveData.setValue(heartRateResultsModels);
 setIsLoading(false);
 , throwable -> 
 setIsLoading(false);
 getNavigator().handleError(throwable);
 ));
 

 public LiveData<ArrayList<HeartRateResultsModel>> getHeartRateResultsLiveData() 
 return heartRateResultsLiveData;
 

6.BindingUtils.java

public final class BindingUtils 

 private BindingUtils() 
 // This class is not publicly instantiable
 


 @BindingAdapter("imageUrl")
 public static void setImageUrl(ImageView imageView, String url) 
 Context context = imageView.getContext();
 Glide.with(context).load(url).into(imageView);
 

 @BindingAdapter("onNavigationItemSelected")
 public static void setOnNavigationItemSelectedListener(
 BottomNavigationView view, OnNavigationItemSelectedListener listener) 
 view.setOnNavigationItemSelectedListener(listener);
 


 @BindingAdapter("adapter")
 public static void addHeartRateResultsItems(RecyclerView recyclerView,
 ArrayList<HeartRateResultsModel> heartRateResultsModels) 
 HeartRateResultsAdapter adapter = (HeartRateResultsAdapter) recyclerView.getAdapter();
 if (adapter != null) 
 adapter.clearItems();
 adapter.addItems(heartRateResultsModels);
 
 

7.DataManager.java

public interface DataManager extends DbHelper, PreferencesHelper, ApiHelper 

8.DbHelper.java

public interface DbHelper 
 Single<ArrayList<HeartRateResultsModel>> getHeartRateResults();

9.AppDataManager.java

public class AppDataManager implements DataManager

 private final ApiHelper mApiHelper;

 private final Context mContext;

 private final DbHelper mDbHelper;

 private final Gson mGson;

 private final PreferencesHelper mPreferencesHelper;

 @Inject
 public AppDataManager(Context context,
 DbHelper dbHelper,
 PreferencesHelper preferencesHelper,
 ApiHelper apiHelper,
 Gson gson) 
 mContext = context;
 mDbHelper = dbHelper;
 mPreferencesHelper = preferencesHelper;
 mApiHelper = apiHelper;
 mGson = gson;
 

 @Override
 public Single<ArrayList<HeartRateResultsModel>> getHeartRateResults() 
 return mDbHelper.getHeartRateResults();
 

10.AppDbHelper.java

@Singleton
public class AppDbHelper implements DbHelper


 private final AppDatabase mAppDatabase;

 @Inject
 public AppDbHelper(AppDatabase appDatabase) 
 this.mAppDatabase = appDatabase;

 



 @Override
 public Single<ArrayList<HeartRateResultsModel>> getHeartRateResults() 
 return Single.fromCallable(new Callable<ArrayList<HeartRateResultsModel>>() 
 @Override
 public ArrayList<HeartRateResultsModel> call() throws Exception 
 ArrayList<HeartRateResultsModel> models = new ArrayList<>();
 models.add(new HeartRateResultsModel("","1"));
 models.add(new HeartRateResultsModel("","2"));
 return models;
 
 );
 

add mViewDataBinding.setLifecycleOwner(this); on method : onViewCreated() at class BaseFragment, like this :

@Override
 public void onViewCreated(@NonNull View view, Bundle savedInstanceState) 
 super.onViewCreated(view, savedInstanceState);
 mViewDataBinding.setVariable(getBindingVariable(), mViewModel);
 mViewDataBinding.setLifecycleOwner(this);
 mViewDataBinding.executePendingBindings();