Android使用Volley解析JSON数组遇类型转换错误，求解决方法

The core issue here is that your server returns a JSONArray as the root response, but your code is using JsonObjectRequest which expects a JSONObject. Let's walk through the fixes step by step:

1. Replace JsonObjectRequest with JsonArrayRequest #

Since the response is a top-level JSONArray, switch to JsonArrayRequest instead of JsonObjectRequest. This eliminates the type mismatch error entirely.

Corrected MyCartActivity Code #

// Initialize your list first (make sure this is done in onCreate)
private List<CartPojo> list = new ArrayList<>();
private CartAdapter adapter;

// ... rest of your onCreate code ...

final JsonArrayRequest request = new JsonArrayRequest(Request.Method.POST, fetchurl, null, 
    new Response.Listener<JSONArray>() {
        @Override
        public void onResponse(JSONArray response) {
            try {
                // Loop directly through the root JSONArray
                for (int i = 0; i < response.length(); i++) {
                    JSONObject object = response.getJSONObject(i);
                    String price = object.getString("Price");
                    String name = object.getString("Items");
                    String quantity = object.getString("Quantity");
                    
                    // Add item to your list
                    list.add(new CartPojo(price, name, quantity));
                }
                
                // Initialize adapter AFTER populating the list (or before, then notify)
                adapter = new CartAdapter(MyCartActivity.this, list);
                // Don't forget to attach the adapter to your ListView/RecyclerView here
                // Example: listView.setAdapter(adapter);
                
                adapter.notifyDataSetChanged();
                progressbar.setVisibility(View.GONE);
                
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    }, 
    new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            error.printStackTrace();
        }
    });

requestQueue.add(request);

2. Improve Adapter Type Safety #

Your adapter uses raw List types, which can lead to runtime errors. Update it to use generic List<CartPojo> for better type checking:

Corrected Adapter Code #

public class CartAdapter extends BaseAdapter { // Assuming you're extending BaseAdapter
    private Activity activity;
    private List<CartPojo> datalist;
    private LayoutInflater inflater;

    public CartAdapter(Activity activity, List<CartPojo> datalist) {
        this.activity = activity;
        this.datalist = datalist;
        this.inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    }

    @Override
    public int getCount() {
        return datalist.size();
    }

    @Override
    public CartPojo getItem(int position) {
        return datalist.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (convertView == null) {
            convertView = inflater.inflate(R.layout.cart_item_layout, parent, false);
        }

        TextView itemName = convertView.findViewById(R.id.item_name);
        TextView price = convertView.findViewById(R.id.item_price);
        TextView quantity = convertView.findViewById(R.id.items_quantity);

        CartPojo pojo = datalist.get(position);
        itemName.setText(pojo.getName());
        price.setText(pojo.getPrice());
        quantity.setText(pojo.getQuantity());

        return convertView;
    }
}

Key Notes: #

• Always match your Volley request type to the root structure of the JSON response (JSONArray vs JSONObject).
• Initialize your list before making the request to avoid null pointer exceptions.
• Move adapter initialization outside the loop (either after populating the list or before the request, then call notifyDataSetChanged() once after adding all items).

内容的提问来源于stack exchange，提问作者Ayush Katuwal