public class CompanyListFragment  extends Fragment {

　　private Activity activity;
　   private ListView companyListView;

　　@Override
　　public View onCreateView(LayoutInflater infalter, ViewGroup container, Bundle savedInstanceState) {
　　　　View view = infalter.inflate(R.layout.companylist_for_sport, container, false);
　　　　companyListView = (ListView)view.findViewById(R.id.companyListView);
　　　　return view;
　　}

}

注意1: 是在 onCreateView 中

注意2: 是 view.findViewById 而不是 activity.findViewById

Resource Reference

• http://www.cnblogs.com/Ken-Cai/p/4186660.html