Android - How to handle multidimensional JSON results into a spinner using Volley library

I have a listview of products displayed on my android app. I am using a web service that returns a JSON. Earlier I had only a flat list of products to display. But now for each list, I have to add a spinner with the variants values from JSON. How do I achieve this?

My present code gives me the below error

com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 168 path $[0].variants

Below is my code :

JSON response

{
"responce": "true",
"top_selling_product": [
{
"product_id": "10",
"product_name": "Palm Ruchi (Pack of 10)",
"product_name_arb": "",
"product_description_arb": "",
"category_id": "8",
"product_description": "",
"variants": [
{
"variant_id": "7",
"variant_name": "2L",
"in_stock": "0",
"price": "120",
"mrp": "130",
"unit_value": "25"
},
{
"variant_id": "8",
"variant_name": "5L",
"in_stock": "1",
"price": "240",
"mrp": "255",
"unit_value": "25"
},
{
"variant_id": "9",
"variant_name": "10L",
"in_stock": "1",
"price": "0",
"mrp": "0",
"unit_value": "0"
}
],
"product_image": "product-placeholder2.jpg",
"status": "",
"unit": "Box",
"increment": "0",
"rewards": "0",
"stock": "",
"title": "Oil"
},
{
"product_id": "11",
"product_name": "Sunflower Sunrich 1 ltr Box(pack of 10)",
"product_name_arb": "",
"product_description_arb": "",
"category_id": "8",
"product_description": "",
"variants": [],
"product_image": "product-placeholder3.jpg",
"status": "",
"unit": "Box",
"increment": "0",
"rewards": "0",
"stock": "",
"title": "Oil"
},
{
"product_id": "26",
"product_name": "TestName4",
"product_name_arb": "",
"product_description_arb": "",
"category_id": "8",
"product_description": "TestAddress4",
"variants": [],
"product_image": "img8",
"status": "",
"unit": "kg",
"increment": "1",
"rewards": "20",
"stock": "",
"title": "Oil"
}
]
}

Top_Selling_model.java

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;



public class Top_Selling_model implements Serializable {

    @SerializedName("product_id")
    @Expose
    private String productId;
    @SerializedName("product_name")
    @Expose
    private String productName;
    @SerializedName("product_name_arb")
    @Expose
    private String productNameArb;
    @SerializedName("product_description_arb")
    @Expose
    private String productDescriptionArb;
    @SerializedName("category_id")
    @Expose
    private String categoryId;
    @SerializedName("product_description")
    @Expose
    private String productDescription;
    @SerializedName("variants")
    @Expose
    private List<VariantsModel> variants = null;
    @SerializedName("product_image")
    @Expose
    private String productImage;
    @SerializedName("status")
    @Expose
    private String status;
    @SerializedName("unit")
    @Expose
    private String unit;
    @SerializedName("increment")
    @Expose
    private String increment;
    @SerializedName("rewards")
    @Expose
    private String rewards;
    @SerializedName("stock")
    @Expose
    private String stock;
    @SerializedName("title")
    @Expose
    private String title;

    public String getProductId() {
        return productId;
    }

    public void setProductId(String productId) {
        this.productId = productId;
    }

    public String getProductName() {
        return productName;
    }

    public void setProductName(String productName) {
        this.productName = productName;
    }

    public String getProductNameArb() {
        return productNameArb;
    }

    public void setProductNameArb(String productNameArb) {
        this.productNameArb = productNameArb;
    }

    public String getProductDescriptionArb() {
        return productDescriptionArb;
    }

    public void setProductDescriptionArb(String productDescriptionArb) {
        this.productDescriptionArb = productDescriptionArb;
    }

    public String getCategoryId() {
        return categoryId;
    }

    public void setCategoryId(String categoryId) {
        this.categoryId = categoryId;
    }

    public String getProductDescription() {
        return productDescription;
    }

    public void setProductDescription(String productDescription) {
        this.productDescription = productDescription;
    }

    public List<VariantsModel> getVariants() {
        return variants;
    }

    public void setVariants(List<VariantsModel> variants) {
        this.variants = variants;
    }

    public String getProductImage() {
        return productImage;
    }

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

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    public String getUnit() {
        return unit;
    }

    public void setUnit(String unit) {
        this.unit = unit;
    }

    public String getIncrement() {
        return increment;
    }

    public void setIncrement(String increment) {
        this.increment = increment;
    }

    public String getRewards() {
        return rewards;
    }

    public void setRewards(String rewards) {
        this.rewards = rewards;
    }

    public String getStock() {
        return stock;
    }

    public void setStock(String stock) {
        this.stock = stock;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }




}

Variants_model.java

import com.google.gson.annotations.Expose;
import com.google.gson.annotations.SerializedName;

import java.io.Serializable;

public class VariantsModel implements Serializable {

    @SerializedName("variant_id")
    @Expose
    private String variantId;
    @SerializedName("variant_name")
    @Expose
    private String variantName;
    @SerializedName("in_stock")
    @Expose
    private String inStock;
    @SerializedName("price")
    @Expose
    private String price;
    @SerializedName("mrp")
    @Expose
    private String mrp;
    @SerializedName("unit_value")
    @Expose
    private String unitValue;

    public String getVariantId() {
        return variantId;
    }

    public void setVariantId(String variantId) {
        this.variantId = variantId;
    }

    public String getVariantName() {
        return variantName;
    }

    public void setVariantName(String variantName) {
        this.variantName = variantName;
    }

    public String getInStock() {
        return inStock;
    }

    public void setInStock(String inStock) {
        this.inStock = inStock;
    }

    public String getPrice() {
        return price;
    }

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

    public String getMrp() {
        return mrp;
    }

    public void setMrp(String mrp) {
        this.mrp = mrp;
    }

    public String getUnitValue() {
        return unitValue;
    }

    public void setUnitValue(String unitValue) {
        this.unitValue = unitValue;
    }

}

Top_selling_Adapter.java

import android.content.Context;
import android.content.SharedPreferences;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.Spinner;
import android.widget.TextView;

import com.bumptech.glide.Glide;
import com.bumptech.glide.load.engine.DiskCacheStrategy;

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

import Config.BaseURL;
import Model.Top_Selling_model;
import gogrocer.tcc.R;

import static android.content.Context.MODE_PRIVATE;


public class Top_Selling_Adapter extends RecyclerView.Adapter<Top_Selling_Adapter.MyViewHolder> {

    private List<Top_Selling_model> modelList;
    ArrayList<String> variantsData = new ArrayList<>();
    private Context context;
SharedPreferences preferences;
    public class MyViewHolder extends RecyclerView.ViewHolder {
        public TextView product_nmae, product_prize;
        public ImageView image;
        public Spinner spinner;

        public MyViewHolder(View view) {
            super(view);
            product_nmae = (TextView) view.findViewById(R.id.product_name);
            product_prize = (TextView) view.findViewById(R.id.product_prize);
            image = (ImageView) view.findViewById(R.id.iv_icon);
            spinner=(Spinner) view.findViewById(R.id.variants);

        }
    }

    public Top_Selling_Adapter(List<Top_Selling_model> modelList) {
        this.modelList = modelList;
    }

    @Override
    public Top_Selling_Adapter.MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.row_top_selling, parent, false);
        context = parent.getContext();
        return new Top_Selling_Adapter.MyViewHolder(itemView);
    }
    @Override
    public void onBindViewHolder(Top_Selling_Adapter.MyViewHolder holder, int position) {
        Top_Selling_model mList = modelList.get(position);
         preferences = context.getSharedPreferences("lan", MODE_PRIVATE);
    String language=preferences.getString("language","");
        Glide.with(context)
                .load(BaseURL.IMG_PRODUCT_URL + mList.getProduct_image())
                .placeholder(R.drawable.icon)
                .crossFade()
                .diskCacheStrategy(DiskCacheStrategy.ALL)
                .dontAnimate()
                .into(holder.image);
      //  variantsData.add(mList.getVariants().getVariantName());
        Log.e("Top_selling_array",mList.getVariants().getVariantName());
        holder.product_prize.setText(context.getResources().getString(R.string.currency) + mList.getVariants().getPrice());
       // Log.e("Top_selling_array",mList.getVariants().toString());
        if (language.contains("english")) {
            holder.product_nmae.setText(mList.getProduct_name());
        }
        else {
            holder.product_nmae.setText(mList.getProduct_name_arb());

        }

    }

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

}

Home_fragment.java

private void make_top_selling() {
        String tag_json_obj = "json_category_req";
        ArrayList<VariantsModel> variantsList = new ArrayList<VariantsModel>();
        isSubcat = false;
        Map<String, String> params = new HashMap<String, String>();
        params.put("parent", "");
        isSubcat = true;
       /* if (parent_id != null && parent_id != "") {
        }*/

        CustomVolleyJsonRequest jsonObjReq = new CustomVolleyJsonRequest(Request.Method.POST,
                BaseURL.GET_TOP_SELLING_PRODUCTS, params, new Response.Listener<JSONObject>() {

            @Override
            public void onResponse(JSONObject response) {
                Log.d(TAG, response.toString());

                try {
                    if (response != null && response.length() > 0) {
                        Boolean status = response.getBoolean("responce");
                        if (status) {
                            Gson gson = new Gson();
                            Type listType = new TypeToken<List<Top_Selling_model>>() {
                            }.getType();
                            Type listType2 = new TypeToken<List<VariantsModel>>() {
                            }.getType();
                            top_selling_models = gson.fromJson(response.getString("top_selling_product"), listType);
                            top_selling_adapter = new Top_Selling_Adapter(top_selling_models);
                            rv_top_selling.setAdapter(top_selling_adapter);
                            top_selling_adapter.notifyDataSetChanged();
                        }
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        }, new Response.ErrorListener() {

            @Override
            public void onErrorResponse(VolleyError error) {
                VolleyLog.d(TAG, "Error: " + error.getMessage());
                if (error instanceof TimeoutError || error instanceof NoConnectionError) {
                    Toast.makeText(getActivity(), getResources().getString(R.string.connection_time_out), Toast.LENGTH_SHORT).show();
                }
            }
        });
        jsonObjReq.setRetryPolicy(new DefaultRetryPolicy(
                retry,
                DefaultRetryPolicy.DEFAULT_MAX_RETRIES,
                DefaultRetryPolicy.DEFAULT_BACKOFF_MULT));
        // Adding request to request queue
        // Adding request to request queue
        AppController.getInstance().addToRequestQueue(jsonObjReq, tag_json_obj);

    }

CustomVolleyJsonRequest.java

public class CustomVolleyJsonRequest extends Request<JSONObject> {

    private Response.Listener<JSONObject> listener;
    private Map<String, String> params;

    public CustomVolleyJsonRequest(String url, Map<String, String> params,
                                   Response.Listener<JSONObject> reponseListener, Response.ErrorListener errorListener) {
        super(Method.GET, url, errorListener);
        this.listener = reponseListener;
        this.params = params;
    }

    public CustomVolleyJsonRequest(int method, String url, Map<String, String> params,
                                   Response.Listener<JSONObject> reponseListener, Response.ErrorListener errorListener) {
        super(method, url, errorListener);
        this.listener = reponseListener;
        this.params = params;
    }

    protected Map<String, String> getParams()
            throws com.android.volley.AuthFailureError {
        return params;
    };

    @Override
    protected Response<JSONObject> parseNetworkResponse(NetworkResponse response) {
        try {
            String jsonString = new String(response.data,
                    HttpHeaderParser.parseCharset(response.headers));
            return Response.success(new JSONObject(jsonString),
                    HttpHeaderParser.parseCacheHeaders(response));
        } catch (UnsupportedEncodingException e) {
            return Response.error(new ParseError(e));
        } catch (JSONException je) {
            return Response.error(new ParseError(je));
        }
    }

    @Override
    protected void deliverResponse(JSONObject response) {
        // TODO Auto-generated method stub
        listener.onResponse(response);
    }
}

EDIT : Changed my POJO classes.

I think there is a problem with your models according to this JsonResponce.
Paste your json response here https://jsoneditoronline.org and see your formatted json and paste your json http://www.jsonschema2pojo.org here for creating your models. In http://www.jsonschema2pojo.org you have to choose Target language Java,
Source type Json, Annotation Style Gson and preview. Get your models from there and try again.

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

for (mList:mList){
   for (variant : Variants){
      variantList.add (variant)
   }
}

<!-- end snippet -->

Firstly create a String list.

List<String> variantNameList = new ArrayList<String>();



for (mList:mList){
   for (variant : Variants){
      variantNameList.add (variant. variant_name)
   }
} 

This is your list which icludes all variant names. Then you need an adapter

// Creating adapter for spinner

ArrayAdapter<String> dataAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_spinner_item,  variantNameList);

// Drop down layout style - list view with radio

buttondataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

// attaching data adapter to spinner

spinner.setAdapter(dataAdapter);

Thats all