我在尝试从 JSON 获取数据时收到此错误

Question

package com.joshbradley.pokemonapp.activities;

import android.annotation.SuppressLint;
import android.os.Bundle;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonArrayRequest;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;
import com.joshbradley.pokemonapp.R;
import com.joshbradley.pokemonapp.adapters.Adapter;
import com.joshbradley.pokemonapp.helperclass.HelperClass;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import java.security.SecureRandom;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.List;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSession;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

public class HomeScreen extends AppCompatActivity {

//VARIABLES

    RecyclerView recyclerView;
    List<HelperClass> helperClasses;
    Adapter adapter;

    private static String JSON_URL_TEST = "https://pokeapi.co/api/v2/pokemon?limit=151";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_home_screen);

//回收器和视图

    recyclerView = findViewById(R.id.home_screen_recycler);
    helperClasses = new ArrayList<>();

//调用提取数据方法extractData（）；

}

//提取数据

private void extractData() {

    RequestQueue queue = Volley.newRequestQueue(this);
    JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(Request.Method.GET, "https://pokeapi.co/api/v2/pokemon?limit=151", null, new Response.Listener<JSONArray>() {
        @Override
        public void onResponse(JSONArray response) {
            for (int i = 0; i < response.length(); i++){
                try {
                    JSONObject jsonObject = response.getJSONObject(i);

                    HelperClass helperClass = new HelperClass();

                    helperClass.setName(jsonObject.getString("name"));
                    helperClass.setImageUrl(jsonObject.getString("url"));
                    helperClasses.add(helperClass);


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

//ADAPTER AND LAYOUT MANAGER

                recyclerView.setLayoutManager(new LinearLayoutManager(getApplicationContext()));
                adapter = new Adapter(getApplicationContext(), helperClasses);
                recyclerView.setAdapter(adapter);
            }

// ERROR RESPONSE 

        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                error.printStackTrace();
            }
        });

        queue.add(jsonArrayRequest);


    }


}
// MY ERROR
com.android.volley.ParseError: org.json.JSONException: Value {"count":1154,"next":"https:\/\/pokeapi.co\/api\/v2\/pokemon?offset=151&limit=151","previous":null,"results":[{"name":"bulbasaur","url":"https:\/\/pokeapi.co\/api\/v2\/pokemon\/1\/"},{"name":"ivysaur","url":"https:\/\/pokeapi.co\/api\/v2\/pokemon\/2\/"},{"name":"venusaur","url":"https:\/\/pokeapi.co\/api\/v2\/pokemon\/3\/"},

Answer 1

在 ExtractData（） 方法中，您有以下内容，这意味着您希望服务响应是 JSON 数组：

JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(Request.Method.GET, ...

如果查看Exception的主体，您将看到服务正在返回一个对象（其中包含一个数组）。

{ "count":1154
, "next":"https:\/\/pokeapi.co\/api\/v2\/pokemon?offset=151&limit=151"
, "previous":null
, "results":[ ... some array of values]
  ... you cut it off so there may be more fields ... 
}

因此，看起来您应该接受一个JSONObject，然后提取与< code>results键相关联的值。我不确定语法，但可能是这样的...

JsonObjectRequest request = new JsonObjectRequest(...
    @Override
    public void onResponse(JSONObject response) {
        JSONArray results = response.getJSONArray("results");
        ....