android - 无法从 Firebase 数据库中获取数据

问题描述

我正在尝试从 firebase 数据库中检索值。但是当我尝试运行应用程序时它崩溃了。这是java文件：package com.example.fresh24；

import android.content.Context;
import android.widget.Toast;

import androidx.annotation.NonNull;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.firestore.FirebaseFirestore;
import com.google.firebase.firestore.QueryDocumentSnapshot;
import com.google.firebase.firestore.QuerySnapshot;

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

public class DBqueries {

    public static FirebaseFirestore firebaseFirestore = FirebaseFirestore.getInstance();
    public static List<MachineCategoryModel> machineCategoryModelList = new ArrayList<>();
    public static List<HomePageModel> homePageModelList = new ArrayList<>();

    public static void loadCategories(final MachineCategoryAdapter machineCategoryAdapter, final Context context){


        firebaseFirestore.collection("CATEGORIES").orderBy("index").get()
                .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
                    @Override
                    public void onComplete(@NonNull Task<QuerySnapshot> task) {
                        if (task.isSuccessful()){
                            for(QueryDocumentSnapshot documentSnapshot : task.getResult()){
                                machineCategoryModelList.add(new MachineCategoryModel(documentSnapshot.get("categoryName").toString()));
                            }
                            machineCategoryAdapter.notifyDataSetChanged();
                        }   else{
                            String error = task.getException().getMessage();
                            Toast.makeText(context,error,Toast.LENGTH_SHORT).show();
                        }
                    }
                });
    }

    public static void loadFragmentData(final HomePageAdapter adapter, final Context context){
        firebaseFirestore.collection("CATEGORIES")
                .document("CoolingCabinet")
                .collection("TRAYS").orderBy("index").get()
                .addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
                    @Override
                    public void onComplete(@NonNull Task<QuerySnapshot> task) {
                        if (task.isSuccessful()){
                            for(QueryDocumentSnapshot documentSnapshot : task.getResult()){
                                if((long)documentSnapshot.get("view_type") == 0){

                                    List<WishlistModel>viewAllProductList = new ArrayList<>();
                                    List<HorizontalProductScrollModel> horizontalProductScrollModelList = new ArrayList<>();
                                    long no_of_products= (long)documentSnapshot.get("no_of_products");
                                    for(long x = 1; x < no_of_products; x++){
                                        horizontalProductScrollModelList.add(new HorizontalProductScrollModel(documentSnapshot.get("product_ID_"+x).toString(),
                                                documentSnapshot.get("product_location_"+x).toString(),
                                                documentSnapshot.get("product_image_"+x).toString(),
                                                documentSnapshot.get("product_title_"+x).toString(),
                                                documentSnapshot.get("product_stock_"+x).toString(),
                                                documentSnapshot.get("product_price_"+x).toString()));

                                        viewAllProductList.add(new WishlistModel(
                                                documentSnapshot.get("product_image_"+x).toString(),
                                                documentSnapshot.get("product_title_"+x).toString(),
                                                (long)documentSnapshot.get("free_coupons_"+x),
                                                documentSnapshot.get("average_rating_"+x).toString(),
                                                (long)documentSnapshot.get("tol_rating_"+x),
                                                documentSnapshot.get("product_price_"+x).toString(),
                                                documentSnapshot.get("product_cut_price_"+x).toString()
                                        ));
                                    }
                                    homePageModelList.add(new HomePageModel(0,documentSnapshot.get("layout_title").toString(),documentSnapshot.get("layout_background").toString(),horizontalProductScrollModelList,viewAllProductList));
                                }
                            }
                            adapter.notifyDataSetChanged();
                        }   else{
                            String error = task.getException().getMessage();
                            Toast.makeText(context,error,Toast.LENGTH_SHORT).show();
                        }
                    }
                });
    }
}

这是我的模型课

package com.example.fresh24;

public class WishlistModel {

    private String productImage;
    private String productTitle;
    private long freeCoupon;
    private String rating;
    private long totalRatings;
    private String productPrice;
    private String cutPrice;

    public WishlistModel(String productImage, String productTitle, long freeCoupon, String rating, long totalRatings, String productPrice, String cutPrice) {
        this.productImage = productImage;
        this.productTitle = productTitle;
        this.freeCoupon = freeCoupon;
        this.rating = rating;
        this.totalRatings = totalRatings;
        this.productPrice = productPrice;
        this.cutPrice = cutPrice;
    }

    public String getProductImage() {
        return productImage;
    }

    public void setProductImage(String productImage) {
        this.productImage = productImage;
    }

    public String getProductTitle() {
        return productTitle;
    }

    public void setProductTitle(String productTitle) {
        this.productTitle = productTitle;
    }

    public long getFreeCoupon() {
        return freeCoupon;
    }

    public void setFreeCoupon(long freeCoupon) {
        this.freeCoupon = freeCoupon;
    }

    public String getRating() {
        return rating;
    }

    public void setRating(String rating) {
        this.rating = rating;
    }

    public long getTotalRatings() {
        return totalRatings;
    }

    public void setTotalRatings(long totalRatings) {
        this.totalRatings = totalRatings;
    }

    public String getProductPrice() {
        return productPrice;
    }

    public void setProductPrice(String productPrice) {
        this.productPrice = productPrice;
    }

    public String getCutPrice() {
        return cutPrice;
    }

    public void setCutPrice(String cutPrice) {
        this.cutPrice = cutPrice;
    }
}

这是适配器文件：

package com.example.fresh24;

import android.content.Intent;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

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

import com.bumptech.glide.Glide;
import com.bumptech.glide.request.RequestOptions;

import java.util.List;

public class WishlistAdapter extends RecyclerView.Adapter<WishlistAdapter.ViewHolder> {

    private List<WishlistModel> wishlistModelList;
    private Boolean wishlist;

    public WishlistAdapter(List<WishlistModel> wishlistModelList, Boolean wishlist) {
        this.wishlistModelList = wishlistModelList;
        this.wishlist = wishlist;
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int viewType) {
        View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.wishlist_item_layout, viewGroup, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull WishlistAdapter.ViewHolder viewHolder, int position) {
        String resource = wishlistModelList.get(position).getProductImage();
        String title = wishlistModelList.get(position).getProductTitle();
        long freeCoupon = wishlistModelList.get(position).getFreeCoupon();
        String rating = wishlistModelList.get(position).getRating();
        long totalRatings = wishlistModelList.get(position).getTotalRatings();
        String productPrice = wishlistModelList.get(position).getProductPrice();
        String cutPrice = wishlistModelList.get(position).getCutPrice();

        viewHolder.setData(resource, title, freeCoupon, rating, totalRatings, productPrice, cutPrice);
    }

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

    public class ViewHolder extends RecyclerView.ViewHolder {
        private ImageView productImage;
        private TextView productTitle;
        private TextView freeCoupons;
        private TextView rating;
        private TextView totalRatings;
        private View priceCut;
        private ImageView couponIcon;
        private TextView productPrice;
        private TextView cutPrice;
        private ImageView deleteBtn;

        public ViewHolder(@NonNull View itemView) {
            super(itemView);
            productImage = itemView.findViewById(R.id.product_image);
            productTitle = itemView.findViewById(R.id.product_title);
            freeCoupons = itemView.findViewById(R.id.free_coupon);
            rating = itemView.findViewById(R.id.tv_product_rating_miniview);
            totalRatings = itemView.findViewById(R.id.total_ratings);
            priceCut = itemView.findViewById(R.id.price_cut);
            couponIcon = itemView.findViewById(R.id.coupon_icon);
            productPrice = itemView.findViewById(R.id.product_price);
            cutPrice = itemView.findViewById(R.id.cut_price);
            deleteBtn = itemView.findViewById(R.id.delete_btn);
        }

        private void setData(String resource, String title, long freeCouponsNo, String averageRate, long totalRatingsNo, String price, String cutPriceValue) {

            Glide.with(itemView.getContext()).load(resource).apply(new RequestOptions().placeholder(R.drawable.home_icon_green)).into(productImage);
            productTitle.setText(title);
            if (freeCouponsNo != 0) {
                couponIcon.setVisibility(View.VISIBLE);
                if (freeCouponsNo == 1) {
                    freeCoupons.setText("free " + freeCouponsNo + " coupon");
                } else {
                    freeCoupons.setText("free " + freeCouponsNo + " coupons");
                }
            }else{
                couponIcon.setVisibility(View.INVISIBLE);
                freeCoupons.setVisibility(View.INVISIBLE);
            }
            rating.setText(averageRate);
            totalRatings.setText(totalRatingsNo+"(ratings)");
            productPrice.setText(price);
            cutPrice.setText(cutPriceValue);

            if(wishlist){
                deleteBtn.setVisibility(View.VISIBLE);
            }else{
                deleteBtn.setVisibility(View.GONE);
            }
            deleteBtn.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Toast.makeText(itemView.getContext(),"Testing Deleted",Toast.LENGTH_SHORT).show();
                }
            });
            itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    Intent productDetailsIntent = new Intent(itemView.getContext(),ProductDetailsActivity.class);
                    itemView.getContext().startActivity(productDetailsIntent);
                }
            });
        }
    }
}

这是 logcat 错误：

Process: com.example.fresh24, PID: 9413
    java.lang.NullPointerException: Attempt to invoke virtual method 'long java.lang.Long.longValue()' on a null object reference
        at com.example.fresh24.DBqueries$2.onComplete(DBqueries.java:68)
        at com.google.android.gms.tasks.zzj.run(Unknown Source)
        at android.os.Handler.handleCallback(Handler.java:751)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:154)
        at android.app.ActivityThread.main(ActivityThread.java:6077)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)

错误出现在 java 文件中的这一行 - (long)documentSnapshot.get("free_coupons_"+x). 我为 Firebase 数据库中的“免费优惠券”和“总评分”字段选择了数字。我已经读到从 firebase 数据库中获取数字字段时会转换为 Long，因此我将它们转换为 long。我无法找到错误的来源。请帮忙。提前致谢。

标签： android

android - 无法从 Firebase 数据库中获取数据

问题描述

解决方案

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