NPEの原因は何ですか？

Question

実行時エラー行27,118,62と134.Logcatもそこにあります。30-35秒後にこれらのエラーが発生しています。

なぜ私はライン上でそれを取得しています27

ライン134：リストビューリストビュー=（リストビュー） getViewメソッド（）findViewById（R.id.list4）。

かもしれないが、NPE

public class Quizze extends android.support.v4.app.Fragment { //line 27 


JSONObject jsonobject; 
JSONArray jsonarray; 
String idno = " "; 



ArrayList<Details> details; 
LinearLayout layout; 
ArrayList<String> nameList; 
TextView textView; 

public Quizze() { 
} 



@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
         Bundle savedInstanceState) { 
    SharedPreferences pref = getActivity().getPreferences(0); 
    pref.getString("url-address", "empty"); 

    new DownloadJSON().execute(); 
    return inflater.inflate(R.layout.quiz_result, container, false); 





} 


class DownloadJSON extends AsyncTask<Void, Void, Void> { //line 62 

    @Override 
    protected Void doInBackground(Void... params) { 


     SharedPreferences pref = getActivity().getPreferences(0); 
     String url = pref.getString("url-address", "empty"); 

     details = new ArrayList<>(); 

     jsonobject = JSONfunctions 
       .getJSONfromURL(url); 

     try { 
      // Locate the NodeList name 
      jsonarray = jsonobject.getJSONArray("results"); 
      for (int i = 0; i < jsonarray.length(); i++) { 
       jsonobject = jsonarray.getJSONObject(i); 
       Collections.reverse(details); 
       if (jsonobject.getString("resType").contains("Multiple Choice Questions")) { 
        { 
         Details detailAll = new Details(); 

         detailAll.setResType(jsonobject.optString("resType")); 
         detailAll.setName(jsonobject.optString("resName")); 
         detailAll.setUrl(jsonobject.optString("resLink")); 
         detailAll.setId(jsonobject.optInt("id")); 


         details.add(detailAll); 
         Collections.reverse(details); 
        } 
       } 

      } 


     } catch (JSONException e) { 
      Log.e("Error", "" + e.getMessage()); 
      e.printStackTrace(); 
     } 
     return null; 


} 

    @Override 
    protected void onPostExecute(Void args) { 


     nameList = new ArrayList<>(); 
     for (Details bean : details) { 
      nameList.add(bean.getResType()); 


      aero(details); //line 118 
     } 
    } 
} 

private void aero(List<Details> mList) { 


    for (Details bean : details) { 
     final String urlChar = bean.getUrl(); 

     idno = String.valueOf(bean.getId()); 

     if (bean.getResType().equals("Multiple Choice Questions")) 

     { 
      ListView listView = (ListView) getView().findViewById(R.id.list4);  //Line 134 

      CustomListViewAdapterMindMaps adapter = new CustomListViewAdapterMindMaps(getContext(), 
        R.layout.quiz_result, mList); 
      listView.setAdapter(adapter); 


      listView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
       @Override 
       public void onItemClick(AdapterView<?> parent, View view, 
             int position, long id) { 


        Toast.makeText(getActivity(), 
          "Click ListItem Number " + idno, Toast.LENGTH_LONG); 


        Intent intent = new Intent(getContext(), Main_Activity_For_Quiz.class); 
        //add data to the Intent object 
        intent.putExtra("idquiz", idno); 
        intent.putExtra("urlchar", urlChar); 
        Toast.makeText(getActivity(), 
          "Click ListItem Number " +idno+ urlChar, Toast.LENGTH_LONG) 
          .show(); 
        //start the second activity 
        startActivity(intent); 

       } 


      }); 
     } 
    } 

    } 
} 




FATAL EXCEPTION: main 
                     Process: com.example.wonder5.player, PID: 21792 
                     java.lang.NullPointerException 
                      at com.example.wonder5.player.Quizze.aero(Quizze.java:134) 
                      at com.example.wonder5.player.Quizze.access$000(Quizze.java:27) 
                      at com.example.wonder5.player.Quizze$DownloadJSON.onPostExecute(Quizze.java:118) 
                      at com.example.wonder5.player.Quizze$DownloadJSON.onPostExecute(Quizze.java:62) 

Answer 1

IDEは、あなたが変更した場合getView()がNULL safe ではないことを警告原因警告ショー：に

ListView listView = (ListView) getView().findViewById(R.id.list4); 

：

ListView listView; 
View view = getView(); 
if(view != null){ 
listView = (ListView) view .findViewById(R.id.list4); 
} 

あなたはもうそれを手に入れません