java - 如何修复 com.android.volley.ParseError: org.json.JSONExeption: Value 我有一个 listview 的自定义适配器，我想从数据库中获取项目列表并使用 json 从 php 构建 CustomArrayAdapter，但问题是我从

Question

我有一个 listview 的自定义适配器，我想从数据库中获取项目列表并使用 json 从 php 构建 CustomArrayAdapter，但问题是我从函数 onErrorResponse 获取 VolleyError 错误。

我通过传递 burger 和 $_POST['category'] 使用邮递员发送了一个帖子请求，并且我得到了这种格式：

    {
    "items": [
    {
        "title": "Beef Burger",
        "price": "10"
    },
    {
        "title": "Pug Burger",
        "price": "12"
    },
    {
        "title": "Green-Chile Burger with Fried Eggs",
        "price": "15"
    },
    {
        "title": "Minetta Burger",
        "price": "8"
    },
    {
        "title": "Cheese Burger",
        "price": "13"
    }
]

}

<?php


$connection = mysqli_connect("localhost", "root", "", "mydb");

if(!$connection){
    die("Connection Failure");
}
else{
    $category = $_POST['category'];
    $response['items'] = array();
    $sql = "SELECT * FROM item WHERE category = '$category'";
    $result = mysqli_query($connection, $sql);
    if((mysqli_num_rows($result)) > 0){
        while($rows = mysqli_fetch_assoc($result)){
            $item['title'] = $rows['title'];
            $item['price'] = $rows['price'];
            array_push($response['items'], $item);  
        }
    }
header('Content-Type: application/json');
echo json_encode($response);
mysqli_close($connection);

}

?>

public class Item extends AppCompatActivity {
List<DataInformation> informationList;
RequestQueue requestQueue;
ListView listView;
String URL = "http://192.168.137.1/MyMobileProject/getItem.php";
DataInformationAdapter adapter;
String category;//the post string
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.itemlayout);

    Bundle bundle = getIntent().getExtras();
    if(bundle != null) {
        category = bundle.getString("category");//can be burger-pizza-drinks
    }
    informationList = new ArrayList<>();
requestQueue = Volley.newRequestQueue(getApplicationContext());

    JsonObjectRequest jsonObjectRequest = new JsonObjectRequest(Request.Method.POST, URL, new Response.Listener<JSONObject>() {

        @Override
        public void onResponse(JSONObject response) {
            try {
                Toast.makeText(getApplicationContext(), "hello", Toast.LENGTH_SHORT).show();
                JSONArray items = response.getJSONArray("items");
                for(int i = 0; i < items.length(); i++){
                    JSONObject item = items.getJSONObject(i);
                    String s1 = item.getString("title");
                    int s2 = item.getInt("price");
                    DataInformation dataInformation = new DataInformation(s1, s2);
                    informationList.add(dataInformation);
                }

            } catch (JSONException e) {
                e.printStackTrace();

            }
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            Toast.makeText(getApplicationContext(), error.toString(), Toast.LENGTH_SHORT).show();
        }
    }){
        @Override
        protected Map<String, String> getParams() throws AuthFailureError {
            Map<String, String> params = new HashMap<>();

            params.put("category", category);//category value is taken from intent
            return params;
        }
    };
    requestQueue.add(jsonObjectRequest);
    adapter = new DataInformationAdapter(Item.this, R.layout.itemlayout2, informationList);
    listView = (ListView)findViewById(R.id.list);
    listView.setAdapter(adapter);

    }

}

List informationList 应该从 php json 编码构建，然后通过 CustomAdapter 并构建 listview。