i am public class MyHomePageAdapter extends BaseAdapter and some code is:
public static class ViewHolder{ public GridView myfriendsGridView; public Button myfriendsPre,myfriendsNext; public ListView listview; public Button searchBu; public Button footerBu; public EditText editText; public ListView myfans_listview; public Button myfans_searchBu; public EditText myfans_editText; } @Override public View getView(int position, View convertView, ViewGroup parent) { int view = getItemViewType(position); if(view==1) { if (convertView == null) { convertView = mInflater.inflate(R.layout.usercenter_myhome_friendschange, null); //holder=new ViewHolder(); holder.listview=(ListView) convertView.findViewById(R.id.myfriend_list); holder.searchBu=(Button) convertView.findViewById(R.id.headbutton); holder.editText=(EditText) convertView.findViewById(R.id.SearchEdit); convertView.setTag(holder); } else { holder=(ViewHolder)convertView.getTag(); } switcher = new ViewSwitcher(context); holder.footerBu = (Button)mInflater.inflate( R.layout.usercenter_myhomepage_myfriends_loadmore, null); holder.footerBu.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub ++counter; switcher.showNext(); //new getMyFriendsMoreItems().execute(); if(NUMBER_OF_ITEMS_IN_COLUMN+counter*NUMBER_OF_MOVE>ConstValue.myfriendsListInfo.size()) { MyFriendssubSet=getDataSubset(0,ConstValue.myfriendsListInfo.size(),ConstValue.myfriendsListInfo); } else { MyFriendssubSet=getDataSubset(0, NUMBER_OF_ITEMS_IN_COLUMN+counter*NUMBER_OF_MOVE,ConstValue.myfriendsListInfo); } if(MyFriendssubSet.size()>0) { adapter.setMasteList(MyFriendssubSet); adapter.notifyDataSetChanged(); } switcher.showPrevious(); Log.i("aa", "rr: "+holder.listview); //holder.listview.setSelection(MyFriendssubSet.size()-1-NUMBER_OF_MOVE); } }); View progress = mInflater.inflate(R.layout.usercenter_myhome_myfriends_loading_footer, null); switcher.addView(holder.footerBu); switcher.addView(progress); holder.listview.addFooterView(switcher); if(ConstValue.myfriendsListInfo.size() > 0) { MyFriendssubSet=getDataSubset(0, NUMBER_OF_ITEMS_IN_COLUMN, ConstValue.myfriendsListInfo); adapter =new FriendsLazyAdapter((Activity) context, MyFriendssubSet); holder.listview.setAdapter(adapter); } i found that my mistake is in this :
switcher.showPrevious(); Log.i("aa", "rr: "+holder.listview); //holder.listview.setSelection(MyFriendssubSet.size()-1-NUMBER_OF_MOVE); the holder.listview=null,so if i delete "//" can call holder.listview.setSelection(MyFriendssubSet.size()-1-NUMBER_OF_MOVE); it weill appear NullPointerException ,so my question how to used the holder.listview so that it not null