如何让FastScroll使用ExpandableListView？

Question

我试图启用ExpandableListView快速滚动，我已经试过此链接中的解决方法解决：android fastScroll only covers part of the list

的问题是，它给了我的NullPointerException错误，每当我扩大群体足以触发快速滚动酒吧。 我试了下面的代码：

MainActivity: 
expandblelist = (ExpandableListView) findViewById(R.id.mexpandablelistview); 
Adapter = new Adapter(this, expandblelist, category_array); 
expandblelist.setAdapter(Adapter); 
expandblelist.setFastScrollEnabled(true); 

Adapter: 
public class Adapter extends BaseExpandableListAdapter 
           implements SectionIndexer, AbsListView.OnScrollListener { 
    private Context mContext; 
    private ExpandableListView mExpandableListView; 
    private List<Category> mGroupCollection; 
    private int[] groupStatus; 
     private boolean manualScroll; 
     private String[] groups; 

    public Adapter(Context context, ExpandableListView pExpandableListView, List<Category> pGroupCollection) { 
     mContext = context; 
     mGroupCollection = pGroupCollection; 
     mExpandableListView = pExpandableListView; 
     groupStatus = new int[mGroupCollection.size()]; 
     setListEvent(); 
     this.mExpandableListView.setOnScrollListener(this); 
    } 

    @Override 
    public void onScrollStateChanged(AbsListView view, int scrollState) { 
     this.manualScroll = scrollState == SCROLL_STATE_TOUCH_SCROLL; 
    } 

    @Override 
    public void onScroll(AbsListView view, 
         int firstVisibleItem, 
         int visibleItemCount, 
         int totalItemCount) {} 

    @Override 
    public int getPositionForSection(int section) { 
     if (manualScroll) { 
      return section; 
     } else {    
      return mExpandableListView.getFlatListPosition(ExpandableListView.getPackedPositionForGroup(section)); 
     } 
    } 

    // Gets called when scrolling the list manually 
    @Override 
    public int getSectionForPosition(int position) { 
     return ExpandableListView.getPackedPositionGroup(mExpandableListView.getExpandableListPosition(position)); 
    } 

    @Override 
    public String[] getSections() { 
    return groups; 
    } 

LogCat: 
NullPointerException 
FastScroller.getThumbPositionForListPosition(FastScroller.java:680) 
FastScroller.onScroll(FastScroller.java:487) 
at android.widget.AbsListView.invokeOnItemScrollListener(AbsListView.java:1337) 

有人可以请指导我吗？ 我非常感谢您的时间和帮助。

非常感谢

Answer 1

要覆盖getSections来回报您的字符串数组“团体”，但数组不会出现在任何地方进行初始化（除非它是在你没有张贴代码完成）。 FastScroller中的mSections被初始化为getSections调用的结果，所以当FastScroller尝试访问该字段时会得到NullPointerException;给你NPE的线路是

final int sectionCount = mSections.length;