瀑布流滚动加载 为何拉到下底不出现

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瀑布流滚动加载 为何拉到下底不出现《

已经显示完了 提示

》 以下是代码 请大神们给看下  谢谢

  <div class="n-title">
                    <div class="bt_wz">
                        <h2><span>{$top['name']}</span></h2>
                        <h3></h3>
                        </div>
                </div>
                                    <div class="navs">
                        <ul>
                            {loop $related $t}
                                            <li class="{if $t.id==$cat.id}current{else}{/if}" >  <a href="{$t['url']}">{$t.name}</a></li>
                                        {/loop}
                        </ul>
                    </div>
                               
                <div class="news">
                    <ul class="news_list" id="content_list">
     
      {template "list_data.html"}   
                    </ul>
                  
                </div>

 

        <div class="margin-top-20" id="is_ajax_btn">
  <br>
            <a href="javascript:dr_ajax_load_more();" class="btn default btn-block"> 加载更多 </a>
   <br>
        </div>
 

<script>
   var Mpage=1;

//滚动显示更多
var scroll_get = true;  //做个标志,不要反反复复的加载
$(document).ready(function () {
    $(window).scroll(function () {
        if (scroll_get==true &&  (400 + $(window).scrollTop())>($(document).height() - $(window).height())) {
            scroll_get = false;
            layer.msg('内容加截中,请稍候',{time:1000});
            dr_ajax_load_more();
        }
    });
});

function dr_ajax_load_more(){
    Mpage++;
    $.get('/index.php?s=api&c=api&m=template&name=list_data.html&module={MOD_DIR}&catid={$catid}&format=json&page='+Mpage+'&'+Math.random(),function(res){
        $('.margin-top-20').hide();
        if(res.code==1){
            if(res.msg==''){
                layer.msg("已经显示完了",{time:500});
            }else{
                $('#content_list').append(res.msg);
                scroll_get = true;
            }
        }else{
            layer.msg(res.msg,{time:2500});
        }
    }, 'json');
}
</script>