ListView的性能优化

@Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder;
        Person person = persons.get(position);
        if (convertView != null) {
            viewHolder = (ViewHolder) convertView.getTag();

        } else {
            convertView = View.inflate(MainActivity.this, R.layout.list_item, null);
            viewHolder = new ViewHolder();
            viewHolder.tv_name = (TextView) convertView.findViewById(R.id.tv_name);
            viewHolder.tv_phone = (TextView) convertView.findViewById(R.id.tv_phone);
            convertView.setTag(viewHolder);
        }
        viewHolder.tv_name.setText("姓名:" + person.getName());
        viewHolder.tv_phone.setText("电话:" + person.getNumber());
        return convertView;
    }
}

static class ViewHolder {
    TextView tv_name;
    TextView tv_phone;
}