list view in fragments null Указатель указателя

Question

Я пытаюсь настроить салфетки для обновления в моем фрагменте, который извлекает объекты из синтаксического анализа. Но каждый раз, кажется, я получаю исключение с нулевым указателем в списке setadapter и list. Хотя оба они правильно инициализированы, не являются нулевыми.

Мой recentsadapter:

package com.astuetz.viewpager.extensions.sample; 

import android.content.Context; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.BaseAdapter; 
import android.widget.TextView; 

import java.util.ArrayList; 
import java.util.HashMap; 

public class RecentsAdapter extends BaseAdapter 
{ 

     LayoutInflater inflater; 
     Context context; 
     ArrayList<HashMap<String,String>> items = null; 

     public RecentsAdapter(Context context,ArrayList<HashMap<String,String>> items) 
     { 
      super(); 
      this.context = context; 
      this.items = items; 
      inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 

     } 

     @Override 
     public int getCount() 
     { 
      return items.size(); 
     } 

     @Override 
     public Object getItem(int position) 
     { 
      return items.get(position); 
     } 

     @Override 
     public long getItemId(int position) 
     { 
      return position; 
     } 

     @Override 
     public View getView(int position, View convertView, ViewGroup parent) 
     { 
      View v = convertView; 
      MyHolder holder = null; 
      if(v == null) 
      { 
       v = inflater.inflate(R.layout.recents_list_item,parent,false); 
       holder = new MyHolder(v); 
       v.setTag(holder); 
      } 

      else 
      { 
       holder = (MyHolder) v.getTag(); 
      } 

      holder.title.setText(items.get(position).get("title")); 
      holder.author.setText(items.get(position).get("author")); 
      holder.dept.setText(items.get(position).get("dept")); 
      holder.price.setText(items.get(position).get("price")); 
    //  holder.place.setText(items.get(position).get("place")); 


      return v; 
     } 

     class MyHolder 
     { 

      TextView dept,title,author,price,place; 

      public MyHolder(View view) 
      { 
       title = (TextView) view.findViewById(R.id.book_title); 
       dept = (TextView)view.findViewById(R.id.dept_name); 
       author = (TextView) view.findViewById(R.id.author_name); 
       price = (TextView)view.findViewById(R.id.price_list); 
    //   place = (TextView)view.findViewById(R.id.place_list); 
      } 

     } 
    } 

Мой recent_card.xml который определяет мой список вид и салфетки, чтобы обновить:

<?xml version="1.0" encoding="utf-8"?> 
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" 
      xmlns:card_view="http://schemas.android.com/apk/res-auto" 
      android:layout_width="match_parent" 
      android:layout_height="match_parent"> 

    <android.support.v4.widget.SwipeRefreshLayout 
     android:id="@+id/container" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent"> 

    <android.support.v7.widget.CardView 
     android:id="@+id/recents_card" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" 
     android:layout_margin="8dp" 
     card_view:cardBackgroundColor="@android:color/white" 
     card_view:cardCornerRadius="8dp" 
     android:padding="8dp"> 

     <ListView 
      android:layout_width="match_parent" 
      android:layout_height="wrap_content" 
      android:id="@+id/recents_list" 
      android:divider="@color/dividerColor" 
      android:dividerHeight="1dp"/> 

    </android.support.v7.widget.CardView> 
    </android.support.v4.widget.SwipeRefreshLayout> 
</FrameLayout> 

и мой RecentsCardFragment.java, который реализует их:

/* 
* Copyright (C) 2013 Andreas Stuetz <andreas.stuetz@gmail.com> 
* 
* Licensed under the Apache License, Version 2.0 (the "License"); 
* you may not use this file except in compliance with the License. 
* You may obtain a copy of the License at 
* 
*  http://www.apache.org/licenses/LICENSE-2.0 
* 
* Unless required by applicable law or agreed to in writing, software 
* distributed under the License is distributed on an "AS IS" BASIS, 
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
* See the License for the specific language governing permissions and 
* limitations under the License. 
*/ 

package com.astuetz.viewpager.extensions.sample; 

import android.app.AlertDialog; 
import android.app.ProgressDialog; 
import android.content.Context; 
import android.net.ConnectivityManager; 
import android.net.NetworkInfo; 
import android.os.Bundle; 
import android.support.v4.app.Fragment; 
import android.support.v4.view.ViewCompat; 
import android.support.v4.widget.SwipeRefreshLayout; 
import android.util.Log; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.Adapter; 
import android.widget.ListView; 
import android.widget.Toast; 


import com.parse.FindCallback; 
import com.parse.GetCallback; 
import com.parse.Parse; 
import com.parse.ParseException; 
import com.parse.ParseObject; 
import com.parse.ParseQuery; 



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



public class RecentsCardFragment extends Fragment implements SwipeRefreshLayout.OnRefreshListener 
{ 
    ListView recentsList = (ListView)getActivity().findViewById(R.id.recents_list); 

    private SwipeRefreshLayout refreshBooks; 

    ArrayList<HashMap<String,String>> items = new ArrayList<>(); 





    //private ProgressDialog progress; 


    public static RecentsCardFragment newInstance() { 
     RecentsCardFragment f = new RecentsCardFragment(); 
      return f; 
     } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     View rootView = inflater.inflate(R.layout.recents_card,container,false); 
     ViewCompat.setElevation(rootView,50); 
     refreshBooks = (SwipeRefreshLayout) rootView.findViewById(R.id.container); 
     refreshBooks.setOnRefreshListener(this); 


     getBooks(); 


     RecentsAdapter adapter = new RecentsAdapter(getActivity().getApplicationContext(), items); 

     recentsList.setAdapter(adapter); 


     return rootView; 
    } 


    private ArrayList<HashMap<String,String>> getBooks(){ 

     final ParseQuery<ParseObject> query = ParseQuery.getQuery("Posted"); 
     query.orderByDescending("createdAt"); 

     query.findInBackground(new FindCallback<ParseObject>() { 


      @Override 
      public void done(List<ParseObject> parseObjects, ParseException e) { 


       if (e == null){ 

        Log.w("Parse","Inside getbooks()"); 
        for (ParseObject book : parseObjects) { 

         HashMap<String, String> test = new HashMap<>(); 

         String dept = book.getString("Department"); 
         String title = book.getString("Title"); 
         String author = book.getString("Author"); 
         Number price_num = book.getNumber("Price"); 
         String price = String.valueOf(price_num); 
         String place = book.getString("Place"); 
         String desp = book.getString("Description"); 

         test.put("dept", dept); 
         test.put("title", title); 
         test.put("author", author); 
         test.put("price", price); 
         test.put("place", place); 
         test.put("description", desp); 

         items.add(test); 




        } 


       } else { 

        Log.d("Books", "Error: " + e.getMessage()); 

       } 

      } 

     }); 

     return items; 
    } 


    @Override 
    public void onRefresh(){ 

     refreshBooks.setRefreshing(true); 
     updateBooks(); 



} 

    private void updateBooks(){ 

     Toast.makeText(getActivity(),"Refresh", Toast.LENGTH_SHORT).show(); 

     items.addAll(getBooks()); 

     refreshBooks.setRefreshing(false); 
    } 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 

    } 


    @Override 
    public void onActivityCreated(Bundle savedInstanceState) { 
     super.onActivityCreated(savedInstanceState); 

    } 


} 

Вот мой LogCat:

06-14 02:44:52.485 2373-2373/com.astuetz.viewpager.extensions.sample I/Process﹕ Sending signal. PID: 2373 SIG: 9 
06-14 02:58:26.624 2502-2524/com.astuetz.viewpager.extensions.sample D/OpenGLRenderer﹕ Render dirty regions requested: true 
06-14 02:58:26.644 2502-2502/com.astuetz.viewpager.extensions.sample D/﹕ HostConnection::get() New Host Connection established 0xabb86710, tid 2502 
06-14 02:58:27.720 2502-2502/com.astuetz.viewpager.extensions.sample D/Atlas﹕ Validating map... 
06-14 02:58:28.692 2502-2502/com.astuetz.viewpager.extensions.sample I/Choreographer﹕ Skipped 57 frames! The application may be doing too much work on its main thread. 
06-14 02:58:28.716 2502-2502/com.astuetz.viewpager.extensions.sample D/AndroidRuntime﹕ Shutting down VM 
06-14 02:58:28.720 2502-2502/com.astuetz.viewpager.extensions.sample E/AndroidRuntime﹕ FATAL EXCEPTION: main 
    Process: com.astuetz.viewpager.extensions.sample, PID: 2502 
    java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.support.v4.app.FragmentActivity.findViewById(int)' on a null object reference 
      at com.astuetz.viewpager.extensions.sample.RecentsCardFragment.<init>(RecentsCardFragment.java:54) 
      at com.astuetz.viewpager.extensions.sample.RecentsCardFragment.newInstance(RecentsCardFragment.java:68) 
      at com.astuetz.viewpager.extensions.sample.MainActivity$MyPagerAdapter.getItem(MainActivity.java:133) 
      at android.support.v4.app.FragmentPagerAdapter.instantiateItem(FragmentPagerAdapter.java:97) 
      at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:837) 
      at android.support.v4.view.ViewPager.populate(ViewPager.java:987) 
      at android.support.v4.view.ViewPager.populate(ViewPager.java:919) 
      at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1441) 
      at android.view.View.measure(View.java:17430) 
      at android.widget.LinearLayout.measureVertical(LinearLayout.java:875) 
      at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) 
      at android.view.View.measure(View.java:17430) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
      at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) 
      at android.view.View.measure(View.java:17430) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
      at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436) 
      at android.widget.LinearLayout.measureVertical(LinearLayout.java:722) 
      at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) 
      at android.view.View.measure(View.java:17430) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
      at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) 
      at android.view.View.measure(View.java:17430) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
      at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436) 
      at android.widget.LinearLayout.measureVertical(LinearLayout.java:722) 
      at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) 
      at android.view.View.measure(View.java:17430) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
      at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) 
      at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2560) 
      at android.view.View.measure(View.java:17430) 
      at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2001) 
      at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1166) 
      at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1372) 
      at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054) 
      at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779) 
      at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767) 
      at android.view.Choreographer.doCallbacks(Choreographer.java:580) 
      at android.view.Choreographer.doFrame(Choreographer.java:550) 
      at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753) 
      at android.os.Handler.handleCallback(Handler.java:739) 
      at android.os.Handler.dispatchMessage(Handler.java:95) 
      at android.os.Looper.loop(Looper.java:135) 
      at android.app.ActivityThread.main(ActivityThread.java:5221) 
      at java.lang.reflect.Method.invoke(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java:372) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 
06-14 02:58:32.992 2502-2502/com.astuetz.viewpager.extensions.sample I/Process﹕ Sending signal. PID: 2502 SIG: 9 

Я продолжаю получать нулевые исключения указатель на мой взгляд, список список Недавних, или на линии, recentslist.ssetadapter (адаптер).

Несмотря на то, что есть несколько ответов на вопросы по одной и той же теме, не в состоянии решить мою проблему, используя их.

, пожалуйста, помогите мне! Спасибо заранее!

Answer 1

Ваш recent_list является недействительным и вы ссылаетесь его вне onCreateView внутри вашего RecentsCardFragment, именно поэтому NullPointerException Происходило. Переместите recent_list объявление в свой метод onCreateView, как это:

public class RecentsCardFragment extends Fragment implements SwipeRefreshLayout.OnRefreshListener 
{ 
    ListView recentsList; 

    private SwipeRefreshLayout refreshBooks; 

    ArrayList<HashMap<String,String>> items = new ArrayList<>(); 

    //private ProgressDialog progress; 

    public static RecentsCardFragment newInstance() { 
     RecentsCardFragment f = new RecentsCardFragment(); 
      return f; 
     } 

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     View rootView = inflater.inflate(R.layout.recents_card,container,false); 
     recentsList = (ListView)rootView.findViewById(R.id.recents_list); 
     ViewCompat.setElevation(rootView,50); 
     refreshBooks = (SwipeRefreshLayout) rootView.findViewById(R.id.container); 
     refreshBooks.setOnRefreshListener(this); 


     getBooks(); 


     RecentsAdapter adapter = new RecentsAdapter(getActivity().getApplicationContext(), items); 

     recentsList.setAdapter(adapter); 


     return rootView; 
    }