Json에서 불러온 파싱 데이터를 리스트뷰에 넣는 과정에서 NullPointerException이 발생합니다

Question

프래그먼트의 리사이클러뷰에 당일 급식을 표시하는 애플리케이션을 제작하려고 합니다. 일단 Json객체가 제대로 불러와지고 읽어지는 것까지는 확인했는데 그걸 리사이클러뷰에 담으려고 하니 NullPointerException이 발생합니다.

 

GalleryFragment.java

public class GalleryFragment extends Fragment {
    long mNow;
    Date mDate;
    SimpleDateFormat mFormat = new SimpleDateFormat("yyyyMMdd");
    String res = ".";


    private GalleryViewModel galleryViewModel;
    private FragmentGalleryBinding binding;

    RecyclerView recyclerView;
    MealAdapter adapter;


public View onCreateView(@NonNull LayoutInflater inflater,
                             ViewGroup container, Bundle savedInstanceState) {
        galleryViewModel =
                new ViewModelProvider(this).get(GalleryViewModel.class);

        binding = FragmentGalleryBinding.inflate(inflater, container, false);
        View root = binding.getRoot();

        recyclerView = root.findViewById(R.id.recyclerView);

      

        adapter = new MealAdapter();
        recyclerView.setAdapter(adapter);


      
        dayNow();

        String urlForm = "https://open.neis.go.kr/hub/mealServiceDietInfo?ATPT_OFCDC_SC_CODE=___&SD_SCHUL_CODE=_______&Type=json&KEY=_";


        final String urlStr = urlForm+"&MLSV_YMD="+dayNow();


        new Thread (new Runnable() {
            @Override
            public void run() {
                request(urlStr);
            }
        }).start();


        //불필요한 부분 제거
        res = res.replace("[{\"head\":[{\"list_total_count\":2},{\"RESULT\":{\"CODE\":\"INFO-000\",\"MESSAGE\":\"정상 처리되었습니다.\"}}]},", "");
        res = res.replace("[{\"head\":[{\"list_total_count\":1},{\"RESULT\":{\"CODE\":\"INFO-000\",\"MESSAGE\":\"정상 처리되었습니다.\"}}]},","");
        res = res.replace("}]}]}", "}]}}");

        TextView textView = root.findViewById(R.id.textView);


      
        return root;
    }

    @Override
    public void onDestroyView() {
        super.onDestroyView();
        binding = null;
    }

    public void request(String urlStr) {
        StringBuilder output = new StringBuilder();
        try {
            URL url = new URL(urlStr);

            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            if (conn != null) {
                conn.setRequestProperty("https.protocols", "TLSv1.2");
                conn.setConnectTimeout(10000);
                conn.setRequestMethod("GET");
                conn.setDoInput(true);

                int resCode = conn.getResponseCode();
                BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
                String line = null;
                while (true) {
                    line = reader.readLine();
                    if (line == null) {
                        break;
                    }

                    output.append(line + "\n");
                }
                reader.close();
                conn.disconnect();

            }
        } catch (Exception ex) {
          
            Log.i(TAG, "request: "+ex.toString());

        }

        res = output.toString();

        processResponse(res);
        
      
    }

    public void processResponse(String res) { 
        Gson gson = new Gson();

        MealList mealList = gson.fromJson(res, MealList.class);
        for (int i = 0; i < mealList.mealServiceDietInfo.row.size(); i++) {   //NullPointerException 발생 지점
            Meal meal = mealList.mealServiceDietInfo.row.get(i);
            adapter.additem(meal);
        }


        adapter.notifyDataSetChanged();
    }

    private String dayNow() {  //당일 날짜
        mNow = System.currentTimeMillis();
        mDate = new Date(mNow);
        return mFormat.format(mDate);
    }


    
}

 

Meal.java

package org.techtown.geubsik;

public class Meal {
    public String ATPT_OFCDC_SC_NM;
    public String SCCUL_NM;
    public String MMEAL_SC_NM;
    public String MLSV_YMN;
    public String DDISH_NM;
    public String ORPLC_INFO;
    public String CAL_INFO;
    public String NTR_INFO;
}

MealList.java

package org.techtown.geubsik;

public class MealList {
    public MealListResult mealServiceDietInfo;
}

 

MealListResult.Java

package org.techtown.geubsik;

import java.util.ArrayList;

public class MealListResult {
    public ArrayList<Meal> row = new ArrayList<Meal>();
}

 

로그캣 메시지

2021-11-07 19:28:16.579 27757-27793/org.techtown.geubsik E/AndroidRuntime: FATAL EXCEPTION: Thread-2
    Process: org.techtown.geubsik, PID: 27757
    java.lang.NullPointerException: Attempt to read from field 'java.util.ArrayList org.techtown.geubsik.MealListResult.row' on a null object reference
        at org.techtown.geubsik.ui.gallery.GalleryFragment.processResponse(GalleryFragment.java:169)
        at org.techtown.geubsik.ui.gallery.GalleryFragment.request(GalleryFragment.java:158)
        at org.techtown.geubsik.ui.gallery.GalleryFragment$1.run(GalleryFragment.java:95)
        at java.lang.Thread.run(Thread.java:761)

Comments

mealList.mealServiceDietInfo가 널입니다. gson 파싱이 제대로 안된 것 같네요.
응답데이터에 mealServiceDietInfo 필드가 존재하는지 잘 확인해 보세요. 참고로 JSON은 case sensitive, 즉 대소문자를 구분합니다.
잘 안되시면 JSON 응답 데이터도 올려보시면 좋을 것 같습니다.