java - 我不断收到此错误“com.google.firebase.database.DatabaseException：无法将 java.lang.String 类型的对象转换为类型”

Question

我正在尝试使用 ReyclerView 和 CardView 从 FireBase 检索数据。当我尝试运行我的系统时，它每次都会崩溃。我认为这是关于数据类型问题。但我找不到解决方案。FirebaseDatabaseHelper.java

package com.example.second_msma;
import androidx.annotation.NonNull;

import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;
import java.util.List;

public class FirebaseDatabaseHelper {
    private FirebaseDatabase mDatabase;
    private DatabaseReference mRefferencevessel;
    private List<VesselBook> vessel = new ArrayList<>();

    public interface DataStatus{
        void DataIsLoaded(List<VesselBook> vessel, List<String> keys);
        void DataIsInserted();
        void DataIsUpdated();
        void DataIsDeleted();

    }

    public FirebaseDatabaseHelper(){
        mDatabase = FirebaseDatabase.getInstance();
        mRefferencevessel = mDatabase.getReference("Bookingvessel");
    }

    public void readVesselBook(final DataStatus dataStatus){
        mRefferencevessel.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                vessel.clear();
                List<String> keys = new ArrayList<>();
                for (DataSnapshot keyNode : dataSnapshot.getChildren()){
                    keys.add(keyNode.getKey());
                    VesselBook vesselBook = keyNode.getValue(VesselBook.class);

                    vessel.add(vesselBook);
                }

                dataStatus.DataIsLoaded(vessel,keys);
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });
    }


}

在这里我总是得到错误VesselBook vesselBook = keyNode.getValue(VesselBook.class);

这是我的 VesselBook.class

package com.example.second_msma;

public class VesselBook {
    private String date;
    private String destination;
    private String origin;
    private String type;
    private  String weight;
    private String id;

    public VesselBook() {
    }

    public VesselBook(String destination, String origin, String type, String weight) {
        this.destination = destination;
        this.origin = origin;
        this.type = type;
        this.weight = weight;
    }

    public VesselBook(String destination, String origin, String type) {
        this.destination = destination;
        this.origin = origin;
        this.type = type;
    }

    public VesselBook(String date, String destination, String origin, String type, String weight, String id) {
        this.date = date;
        this.destination = destination;
        this.origin = origin;
        this.type = type;
        this.weight = weight;
        this.id = id;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public String getDestination() {
        return destination;
    }

    public void setDestination(String destination) {
        this.destination = destination;
    }

    public String getOrigin() {
        return origin;
    }

    public void setOrigin(String origin) {
        this.origin = origin;
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public String getWeight() {
        return weight;
    }

    public void setWeight(String weight) {
        this.weight = weight;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }
}

这是我的 RecyclerViewed_Config.java

package com.example.second_msma;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import java.util.List;

public class RecyclerViewed_Config {
    private Context mContext;
    private BooksAdapter mBookAdapter;
    public void setConfig(RecyclerView recyclerView, Context context, List<VesselBook> vesselBook, List<String> keys){
        mContext = context;
        mBookAdapter = new BooksAdapter(vesselBook,keys);
        recyclerView.setLayoutManager(new LinearLayoutManager(context));
        recyclerView.setAdapter(mBookAdapter);
    }

    class BookItemView extends RecyclerView.ViewHolder{
        private TextView mTitle;
        private TextView mAuthor;
        private TextView mISBN;
        private TextView mCategory;

        private String key;

        public BookItemView(ViewGroup parent){
            super(LayoutInflater.from(mContext).inflate(R.layout.user_list, parent, false));

            mTitle = (TextView) itemView.findViewById(R.id.tvName);
            mAuthor = (TextView) itemView.findViewById(R.id.tvPhone);
            mCategory = (TextView) itemView.findViewById(R.id.tvAddress);
            mISBN = (TextView) itemView.findViewById(R.id.tvISBN);

        }
        public void bind (VesselBook vesselBook, String key){
            mTitle.setText(vesselBook.getOrigin());
            mAuthor.setText(vesselBook.getDestination());
            mCategory.setText(vesselBook.getWeight());
            mISBN.setText(vesselBook.getType());

            this.key = key;

        }
    }

    class BooksAdapter extends RecyclerView.Adapter<BookItemView>{
        private List<VesselBook> mBookList;
        private List<String> mKeys;

        public BooksAdapter(List<VesselBook> mBookList, List<String> mKeys) {
            this.mBookList = mBookList;
            this.mKeys = mKeys;
        }

        @NonNull
        @Override
        public BookItemView onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            return new BookItemView(parent);
        }

        @Override
        public void onBindViewHolder(@NonNull BookItemView holder, int position) {
            holder.bind(mBookList.get(position), mKeys.get(position));

        }

        @Override
        public int getItemCount() {
            return mBookList.size();
        }
    }
}

这是我的数据将被插入到 firebase 的地方

public class BookingVessel extends AppCompatActivity {

    EditText etDate,weight;
    DatabaseReference reff;
    BookngGetter bookingvessel;
    Button book;
    FirebaseDatabase db;
    int maxid =0;
    Spinner mySpinner;

    ArrayAdapter<String> myAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.booking_vessel);

        book = findViewById(R.id.book);
        mySpinner = findViewById(R.id.spinner);
        final Spinner mySpinner1 = findViewById(R.id.spinner2);
        final Spinner mySpinner2 = findViewById(R.id.spinner3);
        weight = findViewById(R.id.weight);
        bookingvessel= new BookngGetter();
        reff = db.getInstance().getReference().child("Bookingvessel");



        myAdapter = new ArrayAdapter<String>(BookingVessel.this,
                android.R.layout.simple_list_item_1,getResources().getStringArray(R.array.origin) );
        myAdapter.setDropDownViewResource(android.R.layout.simple_dropdown_item_1line);
        mySpinner.setAdapter(myAdapter);

        ArrayAdapter<String> myAdapter1 = new ArrayAdapter<String>(BookingVessel.this,
                android.R.layout.simple_list_item_1, getResources().getStringArray(R.array.destination));
        myAdapter1.setDropDownViewResource(android.R.layout.simple_dropdown_item_1line);
        mySpinner1.setAdapter(myAdapter1);

        ArrayAdapter<String> myAdapter2 = new ArrayAdapter<String>(BookingVessel.this,
                android.R.layout.simple_list_item_1, getResources().getStringArray(R.array.shipment));
        myAdapter2.setDropDownViewResource(android.R.layout.simple_dropdown_item_1line);
        mySpinner2.setAdapter(myAdapter2);




        etDate = findViewById(R.id.et_date);

        Calendar calendar = Calendar.getInstance();
        final int year = calendar.get(Calendar.YEAR);
        final int month = calendar.get(Calendar.MONTH);
        final int day = calendar.get(Calendar.DAY_OF_MONTH);


        etDate.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                DatePickerDialog datePickerDialog = new DatePickerDialog(
                        BookingVessel.this, new DatePickerDialog.OnDateSetListener() {
                    @Override
                    public void onDateSet(DatePicker view, int year, int month, int day) {
                        month = month + 1;
                        String date = day + "/" + month + "/" + year;
                        etDate.setText(date);

                    }
                }, year, month, day);
                datePickerDialog.show();

            }
        });





        reff.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                if (dataSnapshot.exists())
                    maxid = (int) dataSnapshot.getChildrenCount();

            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {

            }
        });






        book.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String origin = mySpinner.getSelectedItem().toString().trim();
                String destination = mySpinner1.getSelectedItem().toString().trim();
               String type = mySpinner2.getSelectedItem().toString().trim();
               String date = etDate.getText().toString().trim();


               bookingvessel.setOrigin(mySpinner.getSelectedItem().toString());
               bookingvessel.setDestination(destination);
               bookingvessel.setDate(date);
               bookingvessel.setType(type);
               bookingvessel.setWeight(weight.getText().toString().trim());

                Toast.makeText(BookingVessel.this,"Booking Accepted", Toast.LENGTH_LONG).show();


                reff.child(String.valueOf(maxid+1)).setValue(bookingvessel);

                openFirst();

            }
        });




    }
    public void openFirst(){
        Intent intent = new Intent(this, First.class);
        startActivity(intent);
    }

}

这是我的数据库（Firebase）

标签： javaandroidfirebasefirebase-realtime-database