向下滑动时加载下一页怎么实现

将下面这段程序改成向下滑动加载下一页，移动端的，下面这段是点击下一页按钮加载下一页的程序
$('.next-page').live("click",function(){//下一页
var hasmore = $('input[name=hasmore]').val();
if(hasmore == 'false'){
return false;
}

    var key = parseInt($("input[name=key]").val());
    var order = parseInt($("input[name=order]").val());
    var page = parseInt($("input[name=page]").val());
    var curpage = eval(parseInt($("input[name=curpage]").val())+1);
    var gc_id = parseInt($("input[name=gc_id]").val());
    var keyword = $("input[name=keyword]").val();

    if(gc_id>=0){
        var url = ApiUrl+"/index.php?act=goods&key1="+key1+"&op=goods_list&key="+key+"&order="+order+"&page="+page+"&curpage="+curpage+"&gc_id="+gc_id;
    }else{
        var url = ApiUrl+"/index.php?act=goods&key1="+key1+"&op=goods_list&key="+key+"&order="+order+"&page="+page+"&curpage="+curpage+"&keyword="+keyword;
    }
    $.ajax({
        url:url,
        type:'get',
        dataType:'json',
        success:function(result){
            $("input[name=hasmore]").val(result.hasmore);
            if(!result.hasmore){
                $('.pre-page').removeClass('disabled');
                $('.next-page').addClass('disabled');
            }else{
                $('.pre-page').removeClass('disabled');
            }
            var html = template.render('home_body', result.datas);
            $("#product_list").empty();
            $("#product_list").append(html);
            $("input[name=curpage]").val(curpage);

            var page_total = result.page_total;
            var page_html = '';
            for(var i=1;i<=result.page_total;i++){
                if(i==curpage){
                    page_html+='<option value="'+i+'" selected>'+i+'</option>';
                }else{
                    page_html+='<option value="'+i+'">'+i+'</option>';
                }
            }
            $('select[name=page_list]').empty();
            $('select[name=page_list]').append(page_html);
            pageUrl.push(curpage-1);
            $(window).scrollTop(0);
        }
    });
});

拜托啦  各位大神   急用！！

获取滚动条位置，如果位于底端，获取下一页数据