I have a problem with Livedata observer called multiple time

Question

This is my CartProductItemDao.

    @Dao
public interface CartProductItemDao {

    @Query("select * from CartProductItem where product__category__id = :id")
    LiveData<List<CartProductItem>> getCartProductItemList(int id);

    @Query("select * from CartProductItem where product__id in (:items)")
    LiveData<List<CartProductItem>> getAllProductsSectionItem(ArrayList<Integer> items);

    @Query("Select * from CartProductItem  where product__fav_market_id =:id")
    LiveData<List<CartProductItem>> geAllCartProductItemList(int id);
}

and this is my CartProductItemRepository.

    public class CartProductItemRepository {
    LiveData<List<CartProductItem>> cartProductItemList;
    CartProductItemDao cartProductItemDao;

    public CartProductItemRepository(Application application) {
        TreaderOnlineDatabase treaderOnlineDatabase=TreaderOnlineDatabase.getInstance(application);
        cartProductItemDao=treaderOnlineDatabase.cartProductItemDao();
    }

    public LiveData<List<CartProductItem>> getCartProductItemList(int cat_id) {
        cartProductItemList= cartProductItemDao.getCartProductItemList(cat_id);
        return cartProductItemList;
    }
}

and this is my CartProductItemViewModel.

    public class CartProductItemViewModel extends AndroidViewModel {
    LiveData<List<CartProductItem>> cartProductItemList;
    LiveData<List<CartProductItem>> productSectionItemList;
    LiveData<List<CartProductItem>> allCartProductItem;
    CartProductItemRepository cartProductItemRepository;

    SharedPreferenceClass sharedPreferenceClass;

    public CartProductItemViewModel(@NonNull Application application) {
        super(application);
        cartProductItemRepository=new CartProductItemRepository(application);
        sharedPreferenceClass=new SharedPreferenceClass(getApplication());
        //cartProductItemList=cartProductItemRepository.getCartProductItemList();
    }

    public LiveData<List<CartProductItem>> getCartProductItemList(int id) {
        cartProductItemList=cartProductItemRepository.getCartProductItemList(id);
        return cartProductItemList;
    }
}

and I called getCartProductItemList(cat_is) from inside fragment and this is the code

    @Override
public void recyclerViewOnClick2() {
    CartProductItemViewModel cartProductItemViewModel;
    cartProductItemViewModel=ViewModelProviders.of(this).get(CartProductItemViewModel.class);
    int x=sharedPreferenceClass.getSharedPreferenceCatId();
    cartProductItemViewModel.getCartProductItemList(x).observe(this, new Observer<List<CartProductItem>>() {
        @Override
        public void onChanged(List<CartProductItem> cartProductItems) {
            product_categoriesFragmentAdpter.setArrayList(cartProductItems, getContext());
        }
    });
}

the problem when I make an update or delete for table or insert this observer called multiple times.

Answer 1

The lifecycle of the Fragment can be longer than the lifecycle of the View created. Replace this with viewLifecycleOwner for observing your liveData to avoid double subscriptions :

cartProductItemViewModel.getCartProductItemList(x).observe(viewLifecycleOwner, new Observer<List<CartProductItem>>() {
    @Override
    public void onChanged(List<CartProductItem> cartProductItems) {
        product_categoriesFragmentAdpter.setArrayList(cartProductItems, getContext());
    }
});

Make sure you don't observe liveData before onCreateView(), when using viewLifecycleOwner.

Source: https://developer.android.com/reference/androidx/fragment/app/Fragment.html#getViewLifecycleOwner()

https://www.youtube.com/watch?v=pErTyQpA390&feature=youtu.be