无法将类型 java.lang.String 的对象转换为类型 - FirebaseUI

Question

我不明白问题出在哪里，根据我的说法一切正常。

Logcat:

com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.hamidmadarati.mobilsorgulari.Home.Dashboard.ui.PassengerRecyclerModel at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertBean(CustomClassMapper.java:436) at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.deserializeToClass(CustomClassMapper.java:232) at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertToCustomClass(CustomClassMapper.java:80) at com.google.firebase.database.DataSnapshot.getValue(DataSnapshot.java:203)

片段：

public class PassengerFragment extends Fragment {
    private RecyclerView listVehiclesWeekDay;
    private FirebaseRecyclerOptions<PassengerRecyclerModel> options;
    private FirebaseRecyclerAdapter<PassengerRecyclerModel, PassengerMyViewHolderRecycler> adapter;
    private DatabaseReference databaseReference;

    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_passenger, container,false);

        listVehiclesWeekDay = view.findViewById(R.id.listVehiclesWeekDay);
        listVehiclesWeekDay.setHasFixedSize(true);
        listVehiclesWeekDay.setLayoutManager(new LinearLayoutManager(getActivity()));

        databaseReference = FirebaseDatabase.getInstance().getReference().child("Travels").child("DaysOfTheWeekSimple");
        options = new FirebaseRecyclerOptions.Builder<PassengerRecyclerModel>().setQuery(databaseReference, PassengerRecyclerModel.class).build();
        adapter = new FirebaseRecyclerAdapter<PassengerRecyclerModel, PassengerMyViewHolderRecycler>(options){
            @Override
            protected void onBindViewHolder(@NonNull PassengerMyViewHolderRecycler holder, int position, @NonNull PassengerRecyclerModel model) {
                if (model.getDay() != null){
                    holder.titleTextView.setText(model.getDay());
                }
            }
            @Override
            public PassengerMyViewHolderRecycler onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
                View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.recyclerow, parent, false);
                return new PassengerMyViewHolderRecycler(view);
            }
        };
        adapter.startListening();
        listVehiclesWeekDay.smoothScrollToPosition(0);
        listVehiclesWeekDay.setAdapter(adapter);
        adapter.notifyDataSetChanged();
        return view;
    }
}

Class:

public class PassengerRecyclerModel {
    private String day; //name

    public PassengerRecyclerModel() {
        //Empty - for Firebase Database
    }

    // model
    public PassengerRecyclerModel(String day) {
        this.day = day;
    }

    //Getter and Setter
    public String getDay() {
        return day;
    }
    public void setDay(String day) {
        this.day = day;
    }
}

Answer 1

当您传递以下参考时：

databaseReference = FirebaseDatabase.getInstance().getReference().child("Travels").child("DaysOfTheWeekSimple");

连同“PassengerRecyclerModel”class 到 FirebaseRecyclerOptions.Builder 的“setQuety()”方法，意味着您想使用 Firebase-UI 库来显示所有“PassengerRecyclerModel” " 对象存在于：

Travels -> DaysOfTheWeekSimple

这实际上是不可能的，因为在该引用下它只存在一个 String 类型的子项，因此出现以下错误：

com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.hamidmadarati.mobilsorgulari.Home.Dashboard.ui.PassengerRecyclerModel

要解决这个问题，您需要在“DaysOfTheWeekSimple”节点下添加一个额外的关卡。这可以使用 DatabaseReference 的 push() 方法简单地实现。所以当你在上面的引用处添加一个对象时，像这样添加它：

databaseReference.push().setValue(passengerRecyclerModel);

这样，您的数据库架构应该如下所示：

Firebase-root
  |
  --- Travels
       |
       --- DaysOfTheWeekSimple
             |
             --- $pushedId
                   |
                   --- day: "Day 5: 22-4-2021"

获取数据的代码可以保持不变

编辑：

根据您的评论：

Nope, in fact, we do not create data

如果直接在 Firebase 控制台中添加数据，将无法使用 push()。如果您不想以编程方式添加数据，仍然需要额外的层级。因此，在这种情况下，在“DaysOfTheWeekSimple”节点和“day”属性之间，添加另一个至少包含日期或 ID 的节点，如下所示：

Firebase-root
  |
  --- Travels
       |
       --- DaysOfTheWeekSimple
             |
             --- 22-4-2021 //Extra level added
                   |
                   --- day: "Day 5: 22-4-2021"

the problem is when it is obtained and firebase thinks it is an object and does not convert it to a string

不“思考”，对象的类型为“PassengerRecyclerModel”，应在适配器中相应地读取。

无法将类型 java.lang.String 的对象转换为类型 - FirebaseUI

Can't convert object of type java.lang.String to type - FirebaseUI

java

android

firebase

firebase-realtime-database

firebaseui