为什么标签不显示我的数组元素？

Question

it gives me a bunch of errors in the logcat. but if I delete Log.d("intheclass", questionsArray.get(0)); it shows no errors and app launches. with that code, app doesn't launch. I have tried to LOG the response itself, it works. Absolutely have no idea why this array doesn't work.

package com.example.trivia.data;

import android.util.Log;

import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonArrayRequest;
import com.example.trivia.controller.AppControl;

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

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

public class QuestionBank {
    private String que1;
    String url = "https://raw.githubusercontent.com/curiousily/simple-quiz/master/script/statements.json";
    ArrayList<String> questionsArray= new ArrayList<String>();



    public List<String> getQuestions(){
        JsonArrayRequest bank = new JsonArrayRequest(Request.Method.GET, url, null,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        for(int i=0; i<response.length(); i++){
                            try {
                                que1 = (String) response.getJSONArray(i).get(0);
                                Log.d("queva", String.valueOf(i));
                                questionsArray.add(que1);
                            } catch (JSONException e) {
                                e.printStackTrace();
                            }

                        }
                        //if(callback != null) callback.processFinish(questionsArray);
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {

                    }
                });
        AppControl.getInstance().addToRequestQueue(bank);
        Log.d("intheclass", questionsArray.get(0));
        return questionsArray;
    }
}

Answer 1

it's empty by the time you try to access. When you call getQuestions() it's going to another worker thread to add the values in the questionsArray but your log is on main thread and is in sequence call so it won't work and will give crash.

Possible solution.

public void getQuestions(){
    JsonArrayRequest bank = new JsonArrayRequest(Request.Method.GET, url, null,
            new Response.Listener<JSONArray>() {
                @Override
                public void onResponse(JSONArray response) {
                    for(int i=0; i<response.length(); i++){
                        try {
                            que1 = (String) response.getJSONArray(i).get(0);
                            Log.d("queva", String.valueOf(i));
                            questionsArray.add(que1);
                            doSomething(); //here calling
                        } catch (JSONException e) {
                            e.printStackTrace();
                        }
                    }
                    //if(callback != null) callback.processFinish(questionsArray);
                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {

                }
            });
 }
}

and call this from onRepsonse() after successful api call.

public void doSomething(){
    AppControl.getInstance().addToRequestQueue(bank);
    Log.d("intheclass", questionsArray.get(0));
}