change single item listview android with asynctask

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http://stackoverflow.com – i learning change single item custom listview android with asynctask, i follow this tutorial http://lucasr.org/2012/04/05/performance-tips-for-androids-listview/. but it's seem not work in my listview.. this my code private class ViewHolder { public ImageButton favorite; public TextView jmlh_favorite; protected int position; } public View getView(final int position, View convertView, ViewGroup parent) { View vi=convertView; final ViewHolder holder; if(convertView==null) { vi = infl (HowTos)