1.jquery方法
$(function () {
var elm = $('#pordAttr');
var startPos = $(elm).offset().top;
$.event.add(window, "scroll", function () {
var p = $(window).scrollTop();
$(elm).css('position', ((p) > startPos) ? 'fixed' : 'static');
$(elm).css('top', ((p) > startPos) ? '0px' : "");
});
});
offset()
获取匹配元素在当前视口的相对偏移。
返回的对象包含两个整型属性：top 和 left。此方法只对可见元素有效。
http://www.ostools.net/apidocs/apidoc?api=jquery
2.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=gb2312" /> <title>顶部固定菜单_www.jbxue.com</title> <style type="text/css"> *{ margin:0; padding:0;} .nav-wrapper-fixed{ position:fixed; top:0; width:100%;} .nav-wrapper-fixed .nav{width:960px; margin:0 auto;} .nav-wrapper-fixed .nav li{ float:left; width:100px; margin-right:5px; background:#CCC; text-align:center; height:24px; line-height:24px; list-style:none;} .nav-wrapper{ margin-top:100px; width:100%;} .nav-wrapper .nav{width:960px; margin:0 auto;} .nav-wrapper .nav li{ float:left; width:100px; margin-right:5px; background:#CCC; text-align:center; height:24px; line-height:24px; list-style:none;} </style> <script type="text/javascript"> window.onload = function () { var nav = document.getElementById('nav'); var navFixed = document.getElementById('navFixed'); window.onscroll = function () { var scrollTop = document.documentElement.scrollTop || document.body.scrollTop; document.title = scrollTop if (scrollTop > nav.offsetTop) { navFixed.style.display = 'block'; } else if (scrollTop < nav.offsetTop) { navFixed.style.display = 'none'; } } }; </script> </head> <body style="height:2000px;"> <div class="nav-wrapper"> <div class="nav" id="nav"> <ul> <li>菜单一</li> <li>菜单二</li> <li>菜单三</li> <li>菜单四</li> <li>菜单五</li> </ul> </div> </div> <div class="nav-wrapper-fixed" id="navFixed" style="display:none;"> <div class="nav" id="nav"> <ul> <li>菜单一</li> <li>菜单二</li> <li>菜单三</li> <li>菜单四</li> <li>菜单五</li> </ul> </div> </div> </body> </html>
3
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>自动固定顶部的悬浮菜单栏代码_www.jbxue.com</title> <meta http-equiv="content-type" content="text/html;charset=gb2312"> <style type="text/css"> *{margin:0;padding:0;} ul,li{list-style:none;} #content{width:600px;margin:0 auto;border:1px solid #f00;} ul li.item{width:400px;text-align:center;margin:20px 100px;background:#00f;color:#fff;font-size:14px;font-weight:bold;height:100px;line-height:100px;} #float_banner{position:absolute;top:0;left:50%;width:900px;margin-left:-450px;height:30px;line-height:30px;text-align:center;background:#000;color:#fff;font-size:14px;font-weight:bold;z-index:2;} </style> </head> <body> <div id="float_banner">这里是顶部的横幅，随着页面滚动而浮动</div> <ul id="content"> <li class="item">第一块内容</li> <li class="item">第二块内容</li> <li class="item">第三块内容</li> <li class="item">第四块内容</li> <li class="item">第五块内容</li> <li class="item">第六块内容</li> <li class="item">第七块内容</li> <li class="item">第八块内容</li> <li class="item">第九块内容</li> <li class="item">第十块内容</li> </ul> <script language="javascript"> var speed = 100; var scrollTop = null; var hold = 0; var float_banner; var pos = null; var timer = null; var moveHeight = null; float_banner = document.getElementById("float_banner"); window.onscroll=scroll_ad; function scroll_ad(){ scrollTop = document.documentElement.scrollTop+document.body.scrollTop; pos = scrollTop - float_banner.offsetTop; pos = pos/10 moveHeight = pos>0?Math.ceil(pos):Math.floor(pos); if(moveHeight!=0){ float_banner.style.top = float_banner.offsetTop+moveHeight+"px"; setTimeout(scroll_ad,speed); } //alert(scrollTop); } </script> </body> </html>
另一个：
<script type="text/javascript">
var rollSet = $('#widget');
var offset = rollSet.offset();
var fwidth = $("#footer").height();
$(window).scroll(function() {
var scrollTop = $(window).scrollTop();
var scrollBtm = $(document).height() - $(window).scrollTop() - $("#widget").height();
if (offset.top < scrollTop) {
if (scrollBtm > fwidth) {
rollSet.removeClass('absolute').addClass('fixed')
} else {
rollSet.removeClass('fixed').addClass('absolute')
}
} else {
rollSet.removeClass('fixed')
}
})
</script>
方法说明：
由页面总高度减去已滚动的高度再减去ID为widget的层的高度即等于该层底部距离底部的高度；
当距离底部的高度小于或等于特定位置距离底部的高度时，去掉样式fixed，然后给该层添加绝对定位！
CSS中要给父父层添加position:relative;