は私がフラグメントするには、以下の

Question

をアクティビティを変更した後にNullPointerExceptionエラーが発生します。これは、その下の断片を使用して、別のフラグメントDisplayinListViewにつながるですjson_string = getActivity().getIntent().getExtras().getString("json_data");

09-10 21:56:07.507 22129-22129/com.example.aids.a09application E/AndroidRuntime: FATAL EXCEPTION: main 
                        Process: com.example.aids.a09application, PID: 22129 
                        java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference 
                         at com.example.aids.a09application.DisplayListView.onCreateView(DisplayListView.java:31) 
                         at android.support.v4.app.Fragment.performCreateView(Fragment.java:2192) 
                         at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1299) 
                         at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1528) 
                         at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1595) 
                         at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:758) 
                         at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2363) 
                         at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2149) 
                         at android.support.v4.app.FragmentManagerImpl.optimizeAndExecuteOps(FragmentManager.java:2103) 
                         at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2013) 
                         at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:710) 
                         at android.os.Handler.handleCallback(Handler.java:751) 
                         at android.os.Handler.dispatchMessage(Handler.java:95) 
                         at android.os.Looper.loop(Looper.java:154) 
                         at android.app.ActivityThread.main(ActivityThread.java:6692) 
                         at java.lang.reflect.Method.invoke(Native Method) 
                         at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1468) 
                         at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1358) 

、私は取得していますエラーのためLogcatですこのコードの最後に見つかったフラグメントトランザクション。もともと、これは、DisplayinListViewがアクティビティであったのと同じ意図でしたが、ナビゲーション・ドロワのために、これをフラグメントに変更しました。

public class StandingsList extends Fragment implements View.OnClickListener { 
    //make member variable is Views 
    Button mButton; 
    Button mButton1; 
    TextView mResult; 
    String JSON_RESPONSE; 
    String json_string; 
    FragmentTransaction fragmentTransaction; 

    ProgressDialog mProgressDialog; 


    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
     // Inflate the layout for this fragment 
     View view = inflater.inflate(R.layout.fragment_standings, container, false); 


     //get reference of the views 
     mButton = (Button) view.findViewById(R.id.button); 
     mButton1 = (Button) view.findViewById(R.id.buttontwo); 
     mResult = (TextView) view.findViewById(R.id.result); 
     mButton1.setOnClickListener(this); 

     //when button is clicked 
     mButton.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View view) { 
       //call the getJsonResponse method and fetch the response from the server 
       new getJsonResponse().execute(); 
      } 
     }); 

     return view; 
    } 


     public class getJsonResponse extends AsyncTask<Void, Void, String> { 
      String serverUrl; 

      public getJsonResponse() { 
       mProgressDialog = new ProgressDialog(getActivity()); 
       mProgressDialog.setMessage("Please Wait"); 
       mProgressDialog.setTitle("Processing"); 
       mProgressDialog.setCancelable(false); 
      } 

      @Override 
      protected void onPreExecute() { 

       //set the url from we have to fetch the json response 
       // DO NOT ADD REAL IP. 
       serverUrl = "http://xx.xx.xx.xx/get_info.php"; 
       mProgressDialog.show(); 
      } 

      @Override 
      protected String doInBackground(Void... params) { 
       try { 
        URL url = new URL(serverUrl); 
        HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection(); 
        InputStream inputStream = httpURLConnection.getInputStream(); 
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream)); 
        StringBuilder stringBuilder = new StringBuilder(); 

        while ((JSON_RESPONSE = bufferedReader.readLine()) != null) { 

         stringBuilder.append(JSON_RESPONSE + "\n"); 

        } 

        inputStream.close(); 
        bufferedReader.close(); 
        httpURLConnection.disconnect(); 

        return stringBuilder.toString().trim(); 

       } catch (MalformedURLException e) { 
        Log.e(TAG, "MalformedURLException: " + e); //print exception message to log 
       } catch (IOException e) { 
        Log.e(TAG, "IOException: " + e); //print exception message to log 
       } 
       return null; 
      } 

      @Override 
      protected void onProgressUpdate(Void... values) { 
       super.onProgressUpdate(values); 
      } 

      @Override 
      protected void onPostExecute(String result) { 
       //set the result which is returned by doInBackground() method to result textView 
       mResult.setText(result); 
       mProgressDialog.dismiss(); 
       json_string = result; 
      } 

     } 

      public void onClick(View view){ 

       switch (view.getId()) { 
        case R.id.buttontwo: 
         fragmentTransaction = getFragmentManager().beginTransaction(); 
         fragmentTransaction.replace(main_container, new DisplayListView()); 
         fragmentTransaction.commit(); 
         break; 

       } 


      } 
     } 

これは、エラーは、ライン31上にあるクラスである - 私は活動からのフラグメントに、このクラスを変換するのでjson_string = getActivity().getIntent().getExtras().getString("json_data");

このエラーのみ作成されています。

public class DisplayListView extends Fragment { 

    String json_string; 
    JSONObject jsonObject; 
    JSONArray jsonArray; 
    StandingsAdapter standingsAdapter; 
    ListView listView; 


    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
     // Inflate the layout for this fragment 
     View view = inflater.inflate(R.layout.display_list_view_layout, container, false); 
     listView= (ListView) view.findViewById(R.id.ListViewParse); 
     standingsAdapter = new StandingsAdapter(getActivity(),R.layout.row_layout); 
     listView.setAdapter(standingsAdapter); 
     json_string = getActivity().getIntent().getExtras().getString("json_data"); 
     try { 
      jsonArray = new JSONObject(json_string).getJSONArray("server_response"); 


      int count = 0; 

      int driver_id, team_id, position, points; 
      String firstName, lastName; 



      while(count<jsonArray.length()) 
      { 
       JSONObject JO = jsonArray.getJSONObject(count); 
       driver_id = JO.getInt("Driver_id"); 
       team_id =JO.getInt("Team_id"); 
       firstName = JO.getString("First_name"); 
       lastName= JO.getString("Last_name"); 
       position= JO.getInt("Position"); 
       points = JO.getInt("Points"); 

       Standings standings = new Standings(driver_id, team_id, firstName, lastName, position, points); 
       standingsAdapter.add(standings); 
       count++; 
      } 

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

     return view; 
    } 

} 

Answer 1

によって

json_string = getActivity().getIntent().getExtras().getString("json_data"); 

を置き換える、あなたはargument.Youが私として行うことができますように、データを渡すために持っている新しいFragment.Soであなたの活動を交換しました以下のコードに言及してください。

Bundle bundle = new Bundle(); 
    bundle.putString(Constants.STRING_JSON, json_string); 
    replaceFragment(DisplayListView.newInstance(bundle)); 

ここでは、このjson_stringを実際のフレンドの広告で取得する必要があります。

public static DisplayListView newInstance(Bundle bungle) { 
    DisplayListView fragment = new DisplayListView(); 
    fragment.setArguments(bungle); 
    return fragment;} 

あなたは

String json_string = getArguments().getString(Constants.STRING_JSON); 

Answer 2

今

json_string = getActivity().getIntent().getStringExtra("json_data");