Java com.google.firebase.database.DatabaseException:在com.sale.organicgroups.organicropsonsale.CartData类上找不到要序列化的属性

我正在开发一个Android应用程序，出现以下错误：

2019-05-05 18:19:35.582 9087-9087/com.sale.organiccrops.organiccropsonsale E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.sale.organiccrops.organiccropsonsale, PID: 9087
    com.google.firebase.database.DatabaseException: No properties to serialize found on class com.sale.organiccrops.organiccropsonsale.CartData
        at com.google.firebase.database.core.utilities.encoding.CustomClassMapper$BeanMapper.<init>(com.google.firebase:firebase-database@@16.1.0:535)
        at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.loadOrCreateBeanMapperForClass(com.google.firebase:firebase-database@@16.1.0:317)
        at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.serialize(com.google.firebase:firebase-database@@16.1.0:166)
        at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.serialize(com.google.firebase:firebase-database@@16.1.0:152)
        at com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertToPlainJavaTypes(com.google.firebase:firebase-database@@16.1.0:60)
        at com.google.firebase.database.DatabaseReference.setValueInternal(com.google.firebase:firebase-database@@16.1.0:292)
        at com.google.firebase.database.DatabaseReference.setValue(com.google.firebase:firebase-database@@16.1.0:166)
        at com.sale.organiccrops.organiccropsonsale.CheckoutActivity$2.onClick(CheckoutActivity.java:64)
        at android.view.View.performClick(View.java:6304)
        at android.view.View$PerformClick.run(View.java:24803)
        at android.os.Handler.handleCallback(Handler.java:794)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:176)
        at android.app.ActivityThread.main(ActivityThread.java:6635)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:823)

2019-05-05 18:19:35.582 9087-9087/com.sale.organicgroups.organicropsonsale E/AndroidRuntime:致命异常：main
工艺：com.sale.organicgroups.organicropsonsale，PID:9087
com.google.firebase.database.DatabaseException:在com.sale.organicgroups.organicropsonsale.CartData类上找不到要序列化的属性
位于com.google.firebase.database.core.utilities.encoding.CustomClassMapper$BeanMapper。（com.google.firebase:firebase数据库@@16.1.0:535）
位于com.google.firebase.database.core.utilities.encoding.CustomClassMapper.loadOrCreateBeanMapperForClass（com.google.firebase:firebase数据库@@16.1.0:317）
位于com.google.firebase.database.core.utilities.encoding.CustomClassMapper.serialize（com.google.firebase:firebase数据库@@16.1.0:166）
位于com.google.firebase.database.core.utilities.encoding.CustomClassMapper.serialize（com.google.firebase:firebase数据库@@16.1.0:152）
位于com.google.firebase.database.core.utilities.encoding.CustomClassMapper.convertToPlainJavaTypes（com.google.firebase:firebase数据库@@16.1.0:60）
位于com.google.firebase.database.DatabaseReference.setValueInternal（com.google.firebase:firebase数据库@@16.1.0:292）
位于com.google.firebase.database.DatabaseReference.setValue（com.google.firebase:firebase数据库@@16.1.0:166）
在com.sale.organicgroups.organicropsonsale.CheckoutActivity$2.onClick上（CheckoutActivity.java:64）
在android.view.view.performClick上（view.java:6304）
在android.view.view$PerformClick.run（view.java:24803）
位于android.os.Handler.handleCallback（Handler.java:794）
位于android.os.Handler.dispatchMessage（Handler.java:99）
位于android.os.Looper.loop（Looper.java:176）
位于android.app.ActivityThread.main（ActivityThread.java:6635）
位于java.lang.reflect.Method.invoke（本机方法）
位于com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run（RuntimeInit.java:547）
位于com.android.internal.os.ZygoteInit.main（ZygoteInit.java:823）

CheckoutActivity的Java代码为：

package com.sale.organiccrops.organiccropsonsale;
import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;
import java.util.Objects;
public class CheckoutActivity extends AppCompatActivity {
    private EditText address;
    private DatabaseReference reference;
    private TextView amount;
    private Double sum;
    private ArrayList<CartData> data;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_checkout);
        amount = findViewById(R.id.amount);
        address = findViewById(R.id.address);
        data = new ArrayList<>();
        Button confirm = findViewById(R.id.confirm);
        if (FirebaseAuth.getInstance().getCurrentUser() != null) {
            reference = FirebaseDatabase.getInstance().getReference("users/" + FirebaseAuth.getInstance().getCurrentUser().getUid() + "/cart");
            reference.addListenerForSingleValueEvent(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                    data.clear();
                    sum = 0.0;
                    for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                        data.add(new CartData(snapshot.child("english").getValue(String.class), snapshot.child("hindi").getValue(String.class), snapshot.child("quantity").getValue(String.class), snapshot.child("image").getValue(String.class), snapshot.child("price").getValue()));
                        sum += snapshot.child("price").getValue(Double.class);
                    }
                    amount.setText(new StringBuilder().append("₹ ").append(sum));
                }
                @Override
                public void onCancelled(@NonNull DatabaseError databaseError) {
                }
            });
        }
        confirm.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (address.length() == 0) {
                    address.requestFocus();
                    address.setError("This Is A Required Field");
                } else {
                    reference = FirebaseDatabase.getInstance().getReference("admins/orders/pending").push();
                    reference.child("user").setValue(FirebaseAuth.getInstance().getCurrentUser().getUid());
                    reference.child("address").setValue(address.getText().toString());
                    reference.child("items").setValue(data);
                    reference.child("price").setValue(Double.parseDouble(amount.getText().toString().replace("₹ ", "")));
                    reference = FirebaseDatabase.getInstance().getReference("users/" + FirebaseAuth.getInstance().getCurrentUser().getUid() + "/orders/ongoing").child(Objects.requireNonNull(reference.getKey()));
                    reference.child("address").setValue(address.getText().toString());
                    reference.child("items").setValue(data);
                    reference.child("price").setValue(Double.parseDouble(amount.getText().toString().replace("₹ ", ""))).addOnCompleteListener(new OnCompleteListener<Void>() {
                        @Override
                        public void onComplete(@NonNull Task<Void> task) {
                            if (FirebaseAuth.getInstance().getCurrentUser() != null) {
                                reference = FirebaseDatabase.getInstance().getReference("users/" + FirebaseAuth.getInstance().getCurrentUser().getUid() + "/cart");
                                reference.removeValue().addOnCompleteListener(new OnCompleteListener<Void>() {
                                    @Override
                                    public void onComplete(@NonNull Task<Void> task) {
                                        Toast.makeText(getBaseContext(), "Order Placed Successfully", Toast.LENGTH_SHORT).show();
                                        startActivity(new Intent(getBaseContext(), UserDashboardActivity.class));
                                        finish();
                                    }
                                });
                            }
                        }
                    });
                }
            }
        });
    }
    @Override
    public void onBackPressed() {
        startActivity(new Intent(getBaseContext(), CartActivity.class));
        finish();
    }
    @Override
    protected void onStart() {
        super.onStart();
        if (FirebaseAuth.getInstance().getCurrentUser() == null) {
            startActivity(new Intent(getBaseContext(), AuthenticationActivity.class));
            finish();
        }
    }
    @Override
    protected void onRestart() {
        super.onRestart();
        if (FirebaseAuth.getInstance().getCurrentUser() == null) {
            startActivity(new Intent(getBaseContext(), AuthenticationActivity.class));
            finish();
        }
    }
    @Override
    protected void onResume() {
        super.onResume();
        if (FirebaseAuth.getInstance().getCurrentUser() == null) {
            startActivity(new Intent(getBaseContext(), AuthenticationActivity.class));
            finish();
        }
    }
}

package com.sale.organicgroups.organicropsonsale；
导入android.content.Intent；
导入android.support.annotation.NonNull；
导入android.support.v7.app.AppActivity；
导入android.os.Bundle；
导入android.view.view；
导入android.widget.Button；
导入android.widget.EditText；
导入android.widget.TextView；
导入android.widget.Toast；
导入com.google.android.gms.tasks.OnCompleteListener；
导入com.google.android.gms.tasks.Task；
导入com.google.firebase.auth.FirebaseAuth；
导入com.google.firebase.database.DataSnapshot；
导入com.google.firebase.database.DatabaseError；
导入com.google.firebase.database.DatabaseReference；
导入com.google.firebase.database.FirebaseDatabase；
导入com.google.firebase.database.ValueEventListener；
导入java.util.ArrayList；
导入java.util.Objects；
公共类签出活动扩展了AppCompatActivity{
专用文本地址；
私人数据库参考；
私有文本浏览量；
私人双和；
私有数组列表数据；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity\u checkout）；
金额=findViewById（R.id.金额）；
地址=findViewById（R.id.address）；
数据=新的ArrayList（）；
按钮确认=findViewById（R.id.confirm）；
如果（FirebaseAuth.getInstance（）.getCurrentUser（）！=null）{
reference=FirebaseDatabase.getInstance（）.getReference（“用户/”+FirebaseAuth.getInstance（）.getCurrentUser（）.getUid（）+“/cart”）；
reference.addListenerForSingleValueEvent（新的ValueEventListener（））{
@凌驾
public void onDataChange（@NonNull DataSnapshot DataSnapshot）{
data.clear（）；
总和=0.0；
对于（DataSnapshot快照：DataSnapshot.getChildren（））{
data.add（新的CartData（snapshot.child（“英语”）.getValue（String.class）、snapshot.child（“印地语”）.getValue（String.class）、snapshot.child（“数量”）.getValue（String.class）、snapshot.child（“图像”）.getValue（String.class）、snapshot.child（“价格”）.getValue（））；
sum+=snapshot.child（“price”）.getValue（Double.class）；
}
amount.setText（新的StringBuilder（）.append（“₹ ").追加（总和）；
}
@凌驾
已取消的公共void（@NonNull DatabaseError DatabaseError）{
}
});
}
confirm.setOnClickListener（新视图.OnClickListener（）{
@凌驾
公共void onClick（视图v）{
if（address.length（）==0）{
address.requestFocus（）；
address.setError（“这是必填字段”）；
}否则{
reference=FirebaseDatabase.getInstance（）.getReference（“admins/orders/pending”）.push（）；
reference.child（“user”）.setValue（FirebaseAuth.getInstance（）.getCurrentUser（）.getUid（））；
reference.child（“address”）.setValue（address.getText（）.toString（））；
参考。子项（“项目”）。设定值（数据）；
reference.child（“price”）.setValue（Double.parseDouble（amount.getText（）.toString（）.replace（）₹ ", "")));
reference=FirebaseDatabase.getInstance（）.getReference（“users/”+FirebaseAuth.getInstance（）.getCurrentUser（）.getUid（）+“/orders/consuming”）.child（Objects.requirennull（reference.getKey（））；
reference.child（“address”）.setValue（address.getText（）.toString（））；
参考。子项（“项目”）。设定值（数据）；
package com.sale.organiccrops.organiccropsonsale;

import android.annotation.SuppressLint;
import android.content.Intent;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.TextView;

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

import java.util.ArrayList;
import java.util.Objects;
class CartData {
    private String english, hindi, quantity, url;
    private Object price;
    CartData(String english, String hindi, String quantity, String url, Object price) {
        this.english = english;
        this.hindi = hindi;
        this.quantity = quantity;
        this.url = url;
        this.price = price;
    }
    String getEnglish() {
        return english;
    }
    String getHindi() {
        return hindi;
    }
    String getQuantity() {
        return quantity;
    }
    String getUrl() {
        return url;
    }
    Object getPrice() {
        return price;
    }
    void setPrice(Object price) {
        this.price = price;
    }
}
public class CartActivity extends AppCompatActivity {
    private ProgressBar progress;
    private ArrayList<CartData> data;
    private TextView products;
    private RecyclerView recyclerView;
    private Button checkout;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_cart);
        progress = findViewById(R.id.progress);
        progress.setVisibility(View.VISIBLE);
        products = findViewById(R.id.products);
        checkout = findViewById(R.id.checkout);
        data = new ArrayList<>();
        if (FirebaseAuth.getInstance().getCurrentUser() != null) {
            DatabaseReference reference = FirebaseDatabase.getInstance().getReference("users/" + FirebaseAuth.getInstance().getCurrentUser().getUid() + "/cart");
            reference.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                    data.clear();
                    for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                        data.add(new CartData(snapshot.child("english").getValue(String.class), snapshot.child("hindi").getValue(String.class), snapshot.child("quantity").getValue(String.class), snapshot.child("image").getValue(String.class), snapshot.child("price").getValue()));
                    }
                    progress.setVisibility(View.GONE);
                    if (data.isEmpty()) {
                        products.setVisibility(View.VISIBLE);
                        checkout.setEnabled(false);
                    } else {
                        products.setVisibility(View.GONE);
                        checkout.setEnabled(true);
                        checkout.setOnClickListener(new View.OnClickListener() {
                            @Override
                            public void onClick(View v) {
                                startActivity(new Intent(getBaseContext(), CheckoutActivity.class));
                                finish();
                            }
                        });
                    }
                    recyclerView = findViewById(R.id.recyclerView);
                    recyclerView.setHasFixedSize(true);
                    recyclerView.setLayoutManager(new LinearLayoutManager(getBaseContext()));
                    recyclerView.setAdapter(new CartAdapter(data));
                }
                @Override
                public void onCancelled(@NonNull DatabaseError databaseError) {
                }
            });
        }
    }
    @Override
    public void onBackPressed() {
        startActivity(new Intent(getBaseContext(), UserDashboardActivity.class));
        finish();
    }
    @Override
    protected void onStart() {
        super.onStart();
        if (FirebaseAuth.getInstance().getCurrentUser() == null) {
            startActivity(new Intent(getBaseContext(), AuthenticationActivity.class));
            finish();
        }
    }
    @Override
    protected void onRestart() {
        super.onRestart();
        if (FirebaseAuth.getInstance().getCurrentUser() == null) {
            startActivity(new Intent(getBaseContext(), AuthenticationActivity.class));
            finish();
        }
    }
    @Override
    protected void onResume() {
        super.onResume();
        if (FirebaseAuth.getInstance().getCurrentUser() == null) {
            startActivity(new Intent(getBaseContext(), AuthenticationActivity.class));
            finish();
        }
    }
}
class CartAdapter extends RecyclerView.Adapter<CartAdapter.ViewHolder> {
    private ArrayList<CartData> data;
    private DatabaseReference reference;
    private String key;
    CartAdapter(ArrayList<CartData> data) {
        this.data = data;
    }
    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int viewType) {
        return new ViewHolder(LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.list_cart, viewGroup, false));
    }
    @Override
    public void onBindViewHolder(@NonNull ViewHolder viewHolder, @SuppressLint("RecyclerView") final int i) {
        viewHolder.english.setText(data.get(i).getEnglish());
        viewHolder.hindi.setText(data.get(i).getHindi());
        viewHolder.quantity.setText(data.get(i).getQuantity());
        viewHolder.price.setText(new StringBuilder().append("₹ ").append(data.get(i).getPrice()));
        GlideApp.with(viewHolder.image.getContext()).load(data.get(i).getUrl()).into(viewHolder.image);
        viewHolder.delete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (FirebaseAuth.getInstance().getCurrentUser() != null) {
                    reference = FirebaseDatabase.getInstance().getReference("users/" + FirebaseAuth.getInstance().getCurrentUser().getUid() + "/cart");
                    reference.addListenerForSingleValueEvent(new ValueEventListener() {
                        @Override
                        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                            for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
                                if (Objects.equals(snapshot.child("english").getValue(), data.get(i).getEnglish()) && Objects.equals(snapshot.child("hindi").getValue(), data.get(i).getHindi()) && Objects.equals(snapshot.child("quantity").getValue(), data.get(i).getQuantity()) && Objects.equals(snapshot.child("price").getValue(), data.get(i).getPrice())) {
                                    key = snapshot.getKey();
                                }
                            }
                            if (key != null) {
                                reference.child(key).removeValue();
                            }
                        }
                        @Override
                        public void onCancelled(@NonNull DatabaseError databaseError) {
                        }
                    });
                }
            }
        });
    }
    @Override
    public int getItemCount() {
        return data.size();
    }
    static class ViewHolder extends RecyclerView.ViewHolder {
        private TextView english, hindi, quantity, price;
        private ImageButton delete;
        private ImageView image;
        ViewHolder(View itemView) {
            super(itemView);
            this.english = itemView.findViewById(R.id.english);
            this.hindi = itemView.findViewById(R.id.hindi);
            this.quantity = itemView.findViewById(R.id.quantity);
            this.price = itemView.findViewById(R.id.price);
            this.delete = itemView.findViewById(R.id.delete);
            this.image = itemView.findViewById(R.id.image);
        }
    }
}

void setEnglish() {
       this.english = english;
    }