1首先 ExpandableListView elistview;

         elistview.setGroupIndicator(null);//將控制元件預設的左邊箭頭去掉，

2在 自定義的繼承自BaseExpandableListAdapter的adapter中有一個方法

/**
 * 父類view
 */
    @Override
    public View getGroupView(int groupPosition, boolean isExpanded,
            View convertView, ViewGroup parent) {
        Log.i("zhaoxiong","parent view");
            LinearLayout parentLayout=(LinearLayout) View.inflate(context, R.layout.wowocoupons_parent_item, null);
            TextView parentTextView=(TextView) parentLayout.findViewById(R.id.parentitem);
            parentTextView.setText(parentlist.get(groupPosition));
            ImageView parentImageViw=(ImageView) parentLayout.findViewById(R.id.arrow);

//判斷isExpanded就可以控制是按下還是關閉，同時更換圖片
            if(isExpanded){
                parentImageViw.setBackgroundResource(R.drawable.arrow_down);
            }else{
                parentImageViw.setBackgroundResource(R.drawable.arrow_up);
            }
       
        return parentLayout;
    }