获取tabhost的当前view，并从中取出list，刷新

if (tabHost.getCurrentTabTag().equals("tab2")) {
            LinearLayout listLayout = (LinearLayout) tabHost
                .getCurrentView().findViewById(
                    R.id.downloadmanage_linearlayou);
            Adapter_Download_list downloadList = (Adapter_Download_list) listLayout
                .getChildAt(0);
            downloadList.refreshListData();
        }