在片段PullToRefresh

Question

我有需要刷新的列表，我使用PullToRefresh。我曾经与Activiti合作过，但现在我需要重写片段中的所有内容。当我使用Activiti时，一切正常，但现在我发现了一个错误，当我复制了所有使用相同方法和逻辑的所有内容时，发生了错误nullpointerexception。这是我的片段代码：

private PullToRefreshListView mPullRefreshListView; 

public View onCreateView(LayoutInflater inflater, ViewGroup container, 
     Bundle savedInstanceState) {   
    View view = inflater.inflate(R.layout.fragment_vk, container, false); 
    Map<String, String> networkDetails = getConnectionDetails(); 
    if (networkDetails.isEmpty()) { 
     Toast.makeText(getActivity().getApplicationContext(), 
       "Нет интернет подключения!", Toast.LENGTH_LONG).show(); 
    } 
    getActivity().getActionBar().setDisplayShowTitleEnabled(false); 
    /** Create an array adapter to populate dropdownlist */ 
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(
      getActivity().getBaseContext(), 
      android.R.layout.simple_spinner_dropdown_item, actions); 

    /** Enabling dropdown list navigation for the action bar */ 
    getActivity().getActionBar().setNavigationMode(ActionBar.NAVIGATION_MODE_LIST); 

    /** Defining Navigation listener */ 
    ActionBar.OnNavigationListener navigationListener = new OnNavigationListener() { 

     @Override 
     public boolean onNavigationItemSelected(int itemPosition, 
       long itemId) { 
      switch (itemPosition) { 
      case 1: 
       Intent intent1 = new Intent(getActivity().getApplicationContext(), 
         KfuNews.class); 
       getActivity().finish(); 
       startActivity(intent1); 
       break; 
      } 
      return false; 
     } 
    }; 

    /** 
    * Setting dropdown items and item navigation listener for the actionbar 
    */ 
    getActivity().getActionBar().setListNavigationCallbacks(adapter, navigationListener); 
    boolean firstrun = getActivity().getSharedPreferences("PREFERENCE", getActivity().MODE_PRIVATE) 
      .getBoolean("firstrun", true); 

    // Set a listener to be invoked when the list should be refreshed. 
    mPullRefreshListView 
      .setOnRefreshListener(new OnRefreshListener<ListView>() { 
       @Override 
       public void onRefresh(
         PullToRefreshBase<ListView> refreshView) { 
        String label = DateUtils.formatDateTime(
          getActivity().getApplicationContext(), 
          System.currentTimeMillis(), 
          DateUtils.FORMAT_SHOW_TIME 
            | DateUtils.FORMAT_SHOW_DATE 
            | DateUtils.FORMAT_ABBREV_ALL); 

        // Update the LastUpdatedLabel 
        refreshView.getLoadingLayoutProxy() 
          .setLastUpdatedLabel(label); 

        // Do work to refresh the list here. 
        new GetDataTask().execute(); 
       } 
      }); 

    // Add an end-of-list listener 
    mPullRefreshListView 
      .setOnLastItemVisibleListener(new OnLastItemVisibleListener() { 

       @Override 
       public void onLastItemVisible() { 
        Toast.makeText(getActivity().getApplicationContext(), "End of List!", 
          Toast.LENGTH_SHORT).show(); 
       } 
      }); 
    sp11 = getActivity().getSharedPreferences("VK", 0); 
    editor1 = sp11.edit(); 
    account.restore(getActivity()); 
    if ((firstrun) || (account.access_token == null)) { 
     AlertDialog.Builder builder = new AlertDialog.Builder(getActivity()); 
     builder.setTitle("Авторизация") 
       .setMessage(
         "для просмотра новостей необходимо авторизоваться.") 
       .setCancelable(false) 
       .setPositiveButton("Авторизоваться", 
         new DialogInterface.OnClickListener() { 
          public void onClick(DialogInterface dialog, 
            int id) { 
           editor1.putInt("isVk", 1).commit(); 
           editor1.apply(); 
           startLoginActivity(); 
          } 
         }) 
       .setNegativeButton("Отмена", 
         new DialogInterface.OnClickListener() { 
          public void onClick(DialogInterface dialog, 
            int id) { 
           dialog.cancel(); 
           editor1.putInt("isVk", 0).commit(); 
           editor1.apply(); 
           Intent intent = new Intent(
             getActivity().getApplicationContext(), 
             KfuNews.class); 
           getActivity().finish(); 
           startActivity(intent); 
          } 
         }); 
     AlertDialog alert = builder.create(); 
     alert.show(); 
     // Save the state 
     getActivity().getSharedPreferences("PREFERENCE", getActivity().MODE_PRIVATE).edit() 
       .putBoolean("firstrun", false).commit(); 
    } 
    if (account.access_token != null) { 
     api = new Api(account.access_token, Constants.API_ID); 
    } 
    Log.d("isChange", isChangedStat + ""); 
    getWall(); 
    return view; 
} 

而且我在这行的问题：

mPullRefreshListView 
      .setOnRefreshListener(new OnRefreshListener<ListView>() { 

在那里，我有NullPointerException异常，我没有太多的时间来解决问题，请帮助。

Answer 1

您并未初始化您的mPullRefreshListView变量因此为nullpointerexception。根据你的代码，你是缺少这条线：

mPullRefreshListView = (PullToRefreshListView) view .findViewById(R.id.mPullRefreshListView); 

Answer 2

在片段中启动listview并将侦听器添加到此列表视图的refreshlayout。