一、层跟随屏幕滚动

       <div style="width:120px;height:120px;border:1px solid red; position:absolute; left:800px; top:100px; z-index:1001;" id="AdminUserStateDiv">
        
        </div>
        <div class="div1">层1</div>
        <div class="div2">层2</div>

 <style type="text/css">
        .div1{
    background-color:#FF0000;
    width:2000px;
    height:2000px;
    }

    .div2{
    background-color:#33FF66;
    width:100px;
    height:100px;
    position:fixed;
    left:50px;
    top:50px;
    }
    </style>

<script>

    （1）对文档、屏幕、层的一些jquery基本操作

var showAdminUser = function (obj) {
        var offSet = $(obj).offset();
        var docTop = offSet.top;    //当前元素相对文档top偏移位置
        var docLeft = offSet.left;  //当前元素相对文档left偏移位置

        var docWidth = $(document).width(); //整个页面文档的宽度
        var docHeight = $(document).height();   //整个页面文档的高度
        var dScrollTop = $(document).scrollTop(); //整个文档滚动条相对top位置
        var wScrollTop = $(window).scrollTop(); //整个屏幕滚动条相对top位置
        var winWidth = $(window).width(); //整个屏幕宽度
        var winHeight = $(window).height();//整个屏幕高度

        alert("docWidth: " + docWidth + "——" + "docHeight:" + docHeight + " dScrollTop:" + dScrollTop);


        var dWidth = document.body.offsetWidth;  //纯javascript整个页面文档的宽度
        var hHeight = document.body.offsetHeight;   //纯javascript整个页面文档的高度
        var scrollTop = document.body.scrollTop + document.documentElement.scrollTop
        alert(" docWidth: " + dWidth + " docHeight: " + hHeight + " : " + scrollTop);

    }

　　(2)层伴随滚动条
    $(document).ready(function () {

        $(window).scroll(function () {

            var scrollTop = $(document).scrollTop(); //htm文档滚动对象距离顶部位置
            //alert(scrollTop);

            var AdminUserStateDiv = $("#AdminUserStateDiv");
            //AdminUserStateDiv.css("top", scrollTop + "px");
            AdminUserStateDiv.animate({ "top": scrollTop + "px" }, 0);  //层伴随滚动条滚动，时时改变层对顶部的距离
            //$("#scrollUl").animate({ "marginLeft": scrollposition + "px" }, 10);

        })
    });

</script>

（3）遮罩层和加载图片效果

    <div id="CommonAlertMessageBackg" style="display: none; height: 100%; left: 0; margin: 0; opacity: 0.7; position:absolute; top: 0; visibility: visible; width: 100%; z-index: 998; "> </div>　　//解释：position:absolute;是固定在屏幕上；position:fixed;是系在屏幕上，跟随着滚动条移动的；

    <div id="loadding" style="display: none; position: absolute; z-index: 999;">
        <img src="http://www.mamicode.com/@Url.Content("~/Content/img/loading3.gif")" alt="加载中......" />
    </div>

<script type="text/javascript">
    var ShowLoadding = function () {
        var width = $(window).width();
        var height = $(window).height();
        $("#loadding").css("left", width / 2);
        $("#loadding").css("top", height / 2);
        $("#loadding").show();

        var top = $("#ListContent").offset().top;
        var left = $("#ListContent").offset().left;
        var width = $("#ListContent").width();
        var height = $("#ListContent").height();
        $("#CommonAlertMessageBackg").css({ "top": top, "left": left, "width": width, "height": height });

        $("#CommonAlertMessageBackg").show();
    };
    var HideLoadding = function () {
        $("#loadding").hide();
        $("#CommonAlertMessageBackg").hide();
    };

</script>

跟随屏幕滚动层、遮罩层、获取Div相对定位、整个屏幕、html文档的jquery基本操作