NullPointerException將腳註項添加到Android ListView

Question

我試圖使包含0-2標題和0-1頁腳（基於所需模式）的'動態'列表視圖。 如果我使用的順序

getListView().addFooterView(footerView, null, true); 
getListView().setAdapter(myAdapter); 

我收到一個錯誤：

java.lang.NullPointerException 
at android.widget.AdapterView$AdapterDataSetObserver.onChanged(AdapterView.java:778) 
at android.widget.ListView.addFooterView(ListView.java:364) 
at com.my.fragments.QuestionListFragment.updateList(QuestionListFragment.java:63) 

，如果我行切換到

getListView().setAdapter(myAdapter); 
getListView().addFooterView(footerView, null, true); 

沒有錯誤，但頁腳視圖不會出現在模式更改（它出現在下一次模式更改上，所以我假設代碼正在工作）。

footerView是不是在這一刻運行空

我想不出這裏有什麼問題，但我真的需要頁眉和頁腳是列表視圖的一部分（我可以用它做ScrollView和單獨的框架，但不會這樣做）

更新：要添加的東西：顯示在列表中的數據正在異步加載並存儲在單獨的靜態ArrayList中。我在加載開始和setAdapter（myAdapter）上使用setAdapter（null）完成修改ListView。也許問題在這裏？

UPDATE2 view_question_list_footer.xml

<?xml version="1.0" encoding="utf-8"?> 
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" 
    android:layout_height="wrap_content" android:layout_marginTop="2dip" android:layout_marginBottom="2dip"> 
    <TextView android:textAppearance="?android:attr/textAppearanceSmall" android:layout_height="wrap_content" 
     android:layout_width="wrap_content" android:textStyle="bold" android:text="Load More Questions" android:gravity="center" 
     android:layout_gravity="center" android:lines="3" android:textColor="@android:color/white"></TextView> 
</FrameLayout> 

QuestionAdapter.java

public class QuestionAdapter extends BaseAdapter { 

    public class BrowseSettings { 
     public SortingMode sortingMode  = SortingMode.SORT_BY_DATE; 
     public boolean   isAnswered  = true; 
     public int    categoryFilter = -1; 
     public String   textFilter  = null; 
    } 

    private LayoutInflater inflater   = null; 
    private BrowseSettings settings   = new BrowseSettings(); 
    private LoaderListener loaderListener = null; 

    public QuestionAdapter(Context context, LoaderListener listener) { 
     inflater = LayoutInflater.from(context); 
     loaderListener = listener; 
    } 

    private void loadData() { 
     QAData.questions.clear(); 
     appendData(); 
    } 

    public void appendData() { 
     new QuestionLoaderThread(settings.isAnswered, settings.sortingMode, settings.categoryFilter, settings.textFilter, 
       QAData.questions.getCount(), BaseRequest.DEFAULT_COUNT_VALUE, loaderListener).start(); 
    } 

    public void applyCategoryFilter(int filter) { 
     settings.categoryFilter = filter; 
     loadData(); 
    } 

    public void applyTextFilter(String filter) { 
     settings.textFilter = filter; 
     loadData(); 
    } 

    @Override 
    public int getCount() { 
     return QAData.questions.getCount(); 
    } 

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

    @Override 
    public long getItemId(int position) { 
     return QAData.questions.get(position).getId(); 
    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     QuestionViewHolder viewHolder = null; 
     if(convertView == null) { 
      convertView = inflater.inflate(R.layout.view_question, null); 
      viewHolder = new QuestionViewHolder(); 
      viewHolder.content = (TextView) convertView.findViewById(R.id.QuestionContent); 
      viewHolder.likes = (TextView) convertView.findViewById(R.id.QuestionLikeCounter); 
      viewHolder.question = QAData.questions.get(position); 
      convertView.setTag(viewHolder); 
     } else { 
      viewHolder = (QuestionViewHolder) convertView.getTag(); 
     } 

     viewHolder.content.setText(Html.fromHtml(viewHolder.question.getFormattedQuestion())); 
     viewHolder.likes.setText(String.valueOf(viewHolder.question.getLikesCount())); 

     return convertView; 
    } 

    private class QuestionViewHolder { 
     private TextView content; 
     private TextView likes; 
     private QAQuestion question; 
    } 
} 

Answer 1

嘗試使用getListView().addFooterView(footerView);代替。