Java Firebase JSON到Arraylist内部的Arraylist，存在对象问题 这是我想要创建的JSON对象示例： 这是我创建的类

这是对我有效的解决方案：

for (DataSnapshot postSnapshot : snapshot.getChildren()) {
    ProductEntity upload = postSnapshot.getValue(ProductEntity.class);
    Log.d("error", "onDataChange: " + upload.about);

    List<ProductImage> images = new ArrayList<>() ;
    for(DataSnapshot datas : postSnapshot.child("images").getChildren()){

    ProductImage upload_image = datas.getValue(ProductImage.class);
    images.add(upload_image) ;
    }
    upload.image = images ;
    productList.add(upload);
}

（DataSnapshot postSnapshot:snapshot.getChildren（））的

{
ProductEntity upload=postSnapshot.getValue（ProductEntity.class）；
Log.d（“错误”，“onDataChange:+upload.about”）；
列表图像=新的ArrayList（）；
对于（DataSnapshot数据：postSnapshot.child（“图像”）.getChildren（））{
ProductImage upload\u image=datas.getValue（ProductImage.class）；
添加（上传图片）；
}
upload.image=图像；
productList.add（上传）；
}

class ProductEntity {
    int id;
    String about;
    String contact_vendor;
    String vendor_address;
    String category;
    List<ProductImage> image;
    public String shop_location;

    public ProductEntity(int id, String about, String contact_vendor,
                         String vendor_address, String category, ArrayList<ProductImage> image, String shop_location) {
        this.id = id;
        this.about = about;
        this.contact_vendor = contact_vendor;
        this.vendor_address = vendor_address;
        this.category = category;
        this.image = image;
        this.shop_location = shop_location;
    }

    public ProductEntity() {
    }
}

class ProductImage {
    String url ;

    public ProductImage() {
    }

    public ProductImage(String url) {
        this.url = url;
    }
}

mDatabase = FirebaseDatabase.getInstance().getReference("products");
        mDatabase.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot snapshot) {

                for (DataSnapshot postSnapshot : snapshot.getChildren()) {
                    ProductEntity upload = postSnapshot.getValue(ProductEntity.class);
                    productList.add(upload);
                }

                productsRecyclerAdapter = new ProductsRecyclerAdapter(productList, CategoryActivity.this);
                products.setAdapter(productsRecyclerAdapter);
            }

ProductEntity upload;
mDatabase = FirebaseDatabase.getInstance().getReference("products");
    mDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot snapshot) {

            for (DataSnapshot postSnapshot : snapshot.getChildren()) {
                upload = postSnapshot.getValue(ProductEntity.class);
            for(DataSnapshot datas : postSnapshot.getChildren()){
                  upload=datas.getValue(ProductEntity.class);
                productList.add(upload);
            }
            }
            productsRecyclerAdapter = new ProductsRecyclerAdapter(productList, CategoryActivity.this);
            products.setAdapter(productsRecyclerAdapter);
        }

for (DataSnapshot postSnapshot : snapshot.getChildren()) {
    ProductEntity upload = postSnapshot.getValue(ProductEntity.class);
    Log.d("error", "onDataChange: " + upload.about);

    List<ProductImage> images = new ArrayList<>() ;
    for(DataSnapshot datas : postSnapshot.child("images").getChildren()){

    ProductImage upload_image = datas.getValue(ProductImage.class);
    images.add(upload_image) ;
    }
    upload.image = images ;
    productList.add(upload);
}