getListAdapter（）从ListFragment返回null，getListView工作

Question

按标题，我被堵在这个荒谬的问题

我有一个ListFragment，这里的精简代码：

public class AlarmsListFragment extends ListFragment implements AbsListView.OnItemClickListener { 
    public ListAdapter mAdapter; 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 

     setRetainInstance(true); 

     mAdapter = new AlarmsAdapter(getActivity(), R.layout.alarm_card_item, alarmsList); 
    } 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 

     View view = inflater.inflate(R.layout.fragment_alarms_list, container, false); 

     mListView = (AbsListView) view.findViewById(android.R.id.list); 
     mListView.setAdapter(mAdapter); 

     mListView.setOnItemClickListener(this); 

     return view; 
    } 
} 

而且然后有一个活动：

public class MainActivity extends Activity implements AlarmsListFragment.OnAlarmSelectedListener { 
ListFragment mAlarmsListFragment; 
protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     FragmentManager fm = getFragmentManager(); 
     mAlarmsListFragment = (ListFragment) fm.findFragmentByTag(ALARM_LIST_TAG); 
     if (mAlarmsListFragment == null) 
     { 
      mAlarmsListFragment = new AlarmsListFragment(); 
      getFragmentManager().beginTransaction() 
        .add(R.id.listContainer, mAlarmsListFragment, ALARM_LIST_TAG) 
        .commit(); 
     } 
    } 

后来，onOptionsItemSelected，我有一些代码，需要将项目添加到ListAdapter和无效前面的列表，所以我打电话：

AlarmsAdapter mAdapater = (AlarmsAdapter) mAlarmsListFragment.getListAdapter(); 
mAdapater.add(a); 
mAdapater.notifyDataSetChanged(); 

事情是，我得到一个NullPointerException因为getListAdapter（）返回null，而getListView（）工作正常..什么可能导致这个错误？

Answer 1

你需要调用setListAdapter您ListFragment，即：

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

    setRetainInstance(true); 

    mAdapter = new AlarmsAdapter(getActivity(), R.layout.alarm_card_item, alarmsList); 

    setListAdapter(mAdapter); 
} 

你不需要调用setAdapter您的ListView。 ListFragment将处理它。