如何解决这些问题？ “无法反序列化对象。”

Question

java.lang.RuntimeException：无法反序列化对象。 com.example.knowledgegain.User 类没有定义无参数构造函数。如果您使用 ProGuard，请确保这些构造函数没有被剥离。

或在这种情况下从 Firestore 获取数据的任何其他方式？

show this exception.

problem in this object.

公共类 WalletFragment 扩展 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

应该不在WalletFragment 中添加无参数构造函数。它必须添加到User 类中。为什么？因为在使用以下代码行时，您需要反序列化来自 Firestore 的对象：

user = documentSnapshot.toObject(User.class);

更多信息，请查看我在以下帖子中的回答：

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