ListView ListView rzuca wyjątek NullPointerException, gdy używam własnego ListAdapter

Question

Próbuję wyświetlić dane z mojej bazy danych w ListFragment. Aby to zrobić, śledzę ten sam sposób, gdy używam ListActivity, stworzył własną adapter (adapter może wyglądać dziwnie, I konwertowane go z klasy, która rozciąga BaseAdapter w jednym z moich starych projektów):

package com.mysys.asistan; 

import android.app.ListFragment; 
import android.content.Context; 
import android.database.DataSetObserver; 
import android.os.Bundle; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.ListAdapter; 
import android.widget.TextView; 

import com.mysys.asistan.database.Company; 

public class CompanyListFragment extends ListFragment { 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setListAdapter(new CompanyListAdapter(getActivity())); 
    } 

    private class CompanyListAdapter implements ListAdapter { 

     private final Context context; 
     private DatabaseHelper dbHelper; 

     public CompanyListAdapter(Context context) { 
      this.context = context; 
      this.dbHelper = new DatabaseHelper(context); 
     } 

     public int getCount() { 
      return dbHelper.getCompanyCount(); 
     } 

     public Object getItem(int position) { 
      return dbHelper.getAllCompanies().get(position); 
     } 

     public long getItemId(int position) { 
      return (long) dbHelper.getAllCompanies().get(position).id; 
     } 

     public View getView(int position, View view, ViewGroup parent) { 
      LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
      View row = inflater.inflate(R.layout.company_list_item, parent, false); 
      Company company = (Company) getItem(position); 

      TextView nameView = (TextView) row.findViewById(R.id.CompanyListName); 
      TextView telephoneView = (TextView) row.findViewById(R.id.CompanyListTelephone); 
      TextView addressView = (TextView) row.findViewById(R.id.CompanyListAddress); 

      nameView.setText(company.name); 
      telephoneView.setText(company.telephone); 
      addressView.setText(company.address); 

      return null; 
     } 

     public int getItemViewType(int position) { 
      return IGNORE_ITEM_VIEW_TYPE; 
     } 

     public int getViewTypeCount() { 
      return 1; 
     } 

     public boolean hasStableIds() { 
      return true; 
     } 

     public boolean isEmpty() { 
      return getCount() == 0 ? true : false; 
     } 

     public void registerDataSetObserver(DataSetObserver observer) { 
      // TODO Auto-generated method stub 

     } 

     public void unregisterDataSetObserver(DataSetObserver observer) { 
      // TODO Auto-generated method stub 

     } 

     public boolean areAllItemsEnabled() { 
      return true; 
     } 

     public boolean isEnabled(int position) { 
      return true; 
     } 

    } 
} 

jednak , która prowadzi do NullPointerException i nie mógł zrozumieć nic z dzienników w LogCat, nic związane z mojego kodu:

01-24 20:24:06.040: E/AndroidRuntime(8731): FATAL EXCEPTION: main 
01-24 20:24:06.040: E/AndroidRuntime(8731): java.lang.NullPointerException 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.widget.ListView.measureScrapChild(ListView.java:1181) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.widget.ListView.measureHeightOfChildren(ListView.java:1264) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.widget.ListView.onMeasure(ListView.java:1173) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.view.View.measure(View.java:10848) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4353) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:267) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.view.View.measure(View.java:10848) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4353) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:267) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.view.View.measure(View.java:10848) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4353) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1284) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.widget.LinearLayout.measureHorizontal(LinearLayout.java:956) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:521) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.view.View.measure(View.java:10848) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4353) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:267) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.view.View.measure(View.java:10848) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.widget.LinearLayout.measureVertical(LinearLayout.java:764) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.widget.LinearLayout.onMeasure(LinearLayout.java:519) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.view.View.measure(View.java:10848) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4353) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.widget.FrameLayout.onMeasure(FrameLayout.java:267) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2042) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.view.View.measure(View.java:10848) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.view.ViewRoot.performTraversals(ViewRoot.java:941) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.view.ViewRoot.handleMessage(ViewRoot.java:2063) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.os.Handler.dispatchMessage(Handler.java:99) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.os.Looper.loop(Looper.java:132) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at android.app.ActivityThread.main(ActivityThread.java:4126) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at java.lang.reflect.Method.invokeNative(Native Method) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at java.lang.reflect.Method.invoke(Method.java:491) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:844) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:602) 
01-24 20:24:06.040: E/AndroidRuntime(8731):  at dalvik.system.NativeStart.main(Native Method) 

i to jest układ, który zawiera fragment:

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

    <fragment 
     android:id="@+id/fragment1" 
     android:name="com.mysys.asistan.CompanyListFragment" 
     android:layout_width="@dimen/company_listfragment_width" 
     android:layout_height="wrap_content" /> 

</LinearLayout> 

A to company_list_item.xml:

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

    <TextView android:id="@+id/CompanyListName" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" /> 

    <TextView android:id="@+id/CompanyListAddress" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" /> 

    <TextView android:id="@+id/CompanyListTelephone" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" /> 

</LinearLayout> 

znalazłem this pytanie, ale rozwiązanie to nie jest coś związane z moim problemem, myślę. Z góry dziękuje za twoją pomoc.

Answer 1

Powinieneś zwrócić widok z funkcji getview(). Zwracasz "Null".

 public View getView(int position, View view, ViewGroup parent) { 
     LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
     View row = inflater.inflate(R.layout.company_list_item, parent, false); 
     Company company = (Company) getItem(position); 

     TextView nameView = (TextView) row.findViewById(R.id.CompanyListName); 
     TextView telephoneView = (TextView) row.findViewById(R.id.CompanyListTelephone); 
     TextView addressView = (TextView) row.findViewById(R.id.CompanyListAddress); 

     nameView.setText(company.name); 
     telephoneView.setText(company.telephone); 
     addressView.setText(company.address); 

     return row;//changed from null 
    } 

Uwaga: Użyj widoku z recyklingu i uchwytów, aby przewijanie listy było płynne. Aby uzyskać lepsze zrozumienie przeczytaj ten tutorial.