java - 使用 FirebaseRecyclerAdapter 将 Firebase 实时数据库中的数据检索到 Recycler View 中

Question

我是第一次使用 FirebaseRecyclerAdapter，因此无法使用它并面临一些问题并且无法在屏幕上显示任何数据 HomeFragment 的代码如下

import android.os.Bundle;

import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.WindowManager;

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

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


/**
 * A simple {@link Fragment} subclass.
 * Use the {@link HomeFragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class HomeFragment extends Fragment {

    private RecyclerView recyclerView;
    private ProductAdapter adapter;

    // TODO: Rename parameter arguments, choose names that match
    // the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

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

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment HomeFragment.
     */
    // TODO: Rename and change types and number of parameters
    public static HomeFragment newInstance(String param1, String param2) {
        HomeFragment fragment = new HomeFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1, param1);
        args.putString(ARG_PARAM2, param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View v=  inflater.inflate(R.layout.fragment_home, container, false);
        recyclerView = v.findViewById(R.id.recyclerView);
        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        FirebaseRecyclerOptions<Product> options = new FirebaseRecyclerOptions.Builder<Product>()
                .setQuery(FirebaseDatabase.getInstance().getReference().child(FirebaseAuth.getInstance().getCurrentUser().getUid()), Product.class)
                .build();

        adapter = new ProductAdapter(options);
        recyclerView.setAdapter(adapter);
        return v;
    }

    @Override
    public void onStart() {
        super.onStart();
        adapter.startListening();
    }

    @Override
    public void onStop() {
        super.onStop();
        adapter.stopListening();
    }
}

ProductAdapter 的代码是

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

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

import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.firebase.ui.database.FirebaseRecyclerOptions;

public class ProductAdapter extends FirebaseRecyclerAdapter<Product, ProductAdapter.ProductViewHolder> {

    public ProductAdapter(@NonNull FirebaseRecyclerOptions<Product> options) {
        super(options);
    }

    @Override
    protected void onBindViewHolder(@NonNull ProductViewHolder holder, int position, @NonNull Product model) {
        holder.pname.setText(model.getPname());
        holder.price.setText(model.getPrice());
        holder.description.setText(model.getDescription());
    }

    @NonNull
    @Override
    public ProductViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view= LayoutInflater.from(parent.getContext())
                .inflate(R.layout.item_row, parent, false);

        return new ProductViewHolder(view);
    }

    class ProductViewHolder extends RecyclerView.ViewHolder{
        TextView pname, price, description;
        ImageView image;
        public ProductViewHolder(@NonNull View itemView) {
            super(itemView);
            pname = itemView.findViewById(R.id.product_list_name);
            price = itemView.findViewById(R.id.product_list_price);
            description = itemView.findViewById(R.id.product_list_description);
            image = itemView.findViewById(R.id.product_image);
        }
    }
}

Product类的代码如下

public class Product {
    String pname,price,description,image,date,category,pid,time;
    private boolean expanded;

    public String getDate() {
        return date;
    }

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

    public String getCategory() {
        return category;
    }

    public void setCategory(String category) {
        this.category = category;
    }

    public String getPid() {
        return pid;
    }

    public void setPid(String pid) {
        this.pid = pid;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }

    public Product() {
    }

    public Product(String pname, String price, String description, String image, String date, String category, String pid, String time) {
        this.pname = pname;
        this.price = price;
        this.description = description;
        this.image = image;
        this.date = date;
        this.category = category;
        this.pid = pid;
        this.time = time;
    }

    public String getPname() {
        return pname;
    }

    public void setPname(String pname) {
        this.pname = pname;
    }

    public String getPrice() {
        return price;
    }

    public void setPrice(String price) {
        this.price = price;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getImage() {
        return image;
    }

    public void setImage(String image) {
        this.image = image;
    }

    public boolean isExpanded() {
        return expanded;
    }

    public void setExpanded(boolean expanded) {
        this.expanded = expanded;
    }

    @Override
    public String toString() {
        return "Product{" +
                "pname='" + pname + '\'' +
                ", price='" + price + '\'' +
                ", description='" + description + '\'' +
                ", image='" + image + '\'' +
                ", expanded=" + expanded +
                '}';
    }
}

所以我想从实时数据库中检索产品详细信息，并希望在 fragment 中显示为不同产品的列表

Answer 1

我猜测您的 Product 类中有额外的字段:

在您的 Product 类中:

删除此字段:

private boolean expanded;

也删除这些:

public boolean isExpanded() {
    return expanded;
}

public void setExpanded(boolean expanded) {
    this.expanded = expanded;
}