ViewHolder优化

 @Override    public View getView(int position, View convertView, ViewGroup parent) {        ViewHolder holder=null;        if (convertView == null) {            holder = new ViewHolder();            convertView = View.inflate(context, R.layout.item, null);            holder.tv = (TextView) convertView.findViewById(R.id.tv);            convertView.setTag(holder);        }else{            holder = (ViewHolder) convertView.getTag();        }        holder.tv = (TextView) convertView.findViewById(R.id.tv);        holder.tv.setText(list.get(position).getNews_title());        return convertView;    }    class ViewHolder{        TextView tv;    }