How to solve this problems? " Could not deserialize object. "

Question

java.lang.RuntimeException: Could not deserialize object. Class com.example.knowledgegain.User does not define a no-argument constructor. If you are using ProGuard, make sure these constructors are not stripped.

or any other way of getting data from Firestore in this situation?

show this exception.

problem in this object.

public class WalletFragment extends Fragment {

public WalletFragment() {
    // Required empty public constructor
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

}

FragmentWalletBinding binding;
FirebaseFirestore database;
User user;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    binding = FragmentWalletBinding.inflate(inflater,container,false);
    database = FirebaseFirestore.getInstance();

    try {

        database.collection("User").document(FirebaseAuth.getInstance().getUid())
        .get().addOnSuccessListener(new OnSuccessListener<DocumentSnapshot>() {
            @Override
            public void onSuccess(DocumentSnapshot documentSnapshot) {
                try {

                    user = documentSnapshot.toObject(User.class);
                    binding.showCoinsId.setText(String.valueOf(user.getCoins()));

                }catch (Exception e){
                    Log.e("TAG", "onSuccess: ", e );
                }
            }
        });

    }catch (Exception e){
        Log.d("TAg", e.toString());
        Toast.makeText(getContext(),e.toString(),Toast.LENGTH_LONG).show();
    }

    return binding.getRoot();
}

}

Answer 1

The no-argument constructor should not be added in the WalletFragment. It must be added in the User class. Why? Because you need to deserialize the objects that are coming from the Firestore when using the following line of code:

user = documentSnapshot.toObject(User.class);

For more information, please check my answer from the following post:

• Error in fetching data from Firebase to RecyclerView. FATAL EXCEPTION: ... does not define a no-argument constructor