解决jquery动态增加元素后children值没有变的问题

                    <ul id="attr_input_panel">
                        <li>
                            <div class="attr_input_item">
                                <label class="ui_form_label2">{$lang.attribute}:</label>
                                <select class="querySelect text" name="attr_id[]">
                                <option value="0">{$lang.select_pls}</option>
                                <!--{html_options options=$attributes}-->
                                </select>
                            </div>
                            <div class="attr_input_item">
                                <label class="ui_form_label2">{$lang.value_options}:</label>
                                <textarea class="text" name="value_options[]"></textarea>
                            </div>
                            <div class="attr_input_item">
                                <label class="ui_form_label2">{$lang.def_value}:</label>
                                <input class="text" type="text" name="def_value[]" size="32" value="" />
                            </div>
                            <div class="attr_input_item">
                                <label class="ui_form_label2">{$lang.unit}:</label>
                                <input class="text" type="text" name="unit[]" size="8" value="" />
                            </div>
                        </li>
                          <li><input class="formbtn right" id="add_goodsattr" type="button" name="add_goodsattr" value="{$lang.add_goodsattr}" /></li>
                    </ul>

    $(‘#add_goodsattr‘).click(function(){
        alert($(‘#attr_input_panel‘).children().length);
        $(this).before(‘<li><div class="attr_input_item">‘+
                ‘<label class="ui_form_label2">{$lang.attribute}:</label>‘+
                    ‘<select class="querySelect text" name="attr_id[]">‘+
                    ‘<option value="0">{$lang.select_pls}</option>‘+
                    ‘{html_options options=$attributes}‘+
                    ‘</select></div><div class="attr_input_item">‘+
                    ‘<label class="ui_form_label2">{$lang.value_options}:</label>‘+
                    ‘<textarea class="text" name="value_options[]"></textarea></div><div class="attr_input_item">‘+
                    ‘<label class="ui_form_label2">{$lang.def_value}:</label>‘+
                    ‘<input class="text" type="text" name="def_value[]" size="32" value="" /></div><div class="attr_input_item">‘+
                    ‘<label class="ui_form_label2">{$lang.unit}:</label>‘+
                    ‘<input class="text" type="text" name="unit[]" size="8" value="" /></div>‘+
                ‘</li>‘);
    });

alert($(‘#attr_input_panel‘).find(‘li‘).length);