getView方法中，判断view是否为空时一直报空指针异常，对了一遍代码，没问题啊

public View getView(int position, View view, ViewGroup viewGroup) {

   WordButton holder;

   if (view == null) {
       view = LayoutInflater.from(mContext).inflate(R.layout.gridview_item, null);

       holder = (WordButton) getItem(position);
       holder.mIndex = position;
       holder.mBtnWord = (Button) findViewById(R.id.id_btn_word);

       view.setTag(holder);
   } else {
       holder = (WordButton) view.getTag();
   }

   holder.mBtnWord.setText(holder.mStrWord);
   return view;

}