一、引言

好多人都问，织梦的下拉导航怎么做呢？其实很简单！即使你对代码一点也不熟悉，没关系！

按照我的步骤走！记住一步也不能错哦！

二、实现过程

1、首先：

将下面这段代码贴到templets\default\footer.htm文件里（只要在此文件里就行，位置无所谓啦！自己看着办！）

 <!-- //二级子类下拉菜单，考虑SEO原因放置于底部 -->

    <script type='text/javascript' src='{dede:global.cfg_cmsurl/}/images/js/dropdown.js'></script>

    {dede:channelartlist typeid='top' cacheid='channelsonlist'}

    <ul id="dropmenu{dede:field.typeid/}" class="dropMenu">

        {dede:channel type='son' noself='yes'}

        <li><a href="[field:typelink/]">[field:typename/]</a></li>

        {/dede:channel}

    </ul>

    {/dede:channelartlist}

    <script type="text/javascript">cssdropdown.startchrome("navMenu")</script>

以上代码可以看出，二级子类下拉菜单是由dropdown.js控制的，我们来看dropdown.js文件：

由以上的cssdropdown.startchrome("navMenu")，可以看出我们调用的是  startchrome:function()

var cssdropdown={

disappeardelay: 250,

disablemenuclick: false,

enableswipe: 1,

enableiframeshim: 1,

dropmenuobj: null, ie: document.all, firefox: document.getElementById&&!document.all, swipetimer: undefined, bottomclip:0,

getposOffset:function(what, offsettype){

var totaloffset=(offsettype=="left")? what.offsetLeft : what.offsetTop;

var parentEl=what.offsetParent;

while (parentEl!=null){

totaloffset=(offsettype=="left")? totaloffset+parentEl.offsetLeft : totaloffset+parentEl.offsetTop;

parentEl=parentEl.offsetParent;

}

return totaloffset;

},

swipeeffect:function(){

if (this.bottomclip<parseInt(this.dropmenuobj.offsetHeight)){

this.bottomclip+=10+(this.bottomclip/10)

this.dropmenuobj.style.clip="rect(0 auto "+this.bottomclip+"px 0)"

}

else

return

this.swipetimer=setTimeout("cssdropdown.swipeeffect()", 10)

},

showhide:function(obj, e){

if (this.ie || this.firefox)

this.dropmenuobj.style.left=this.dropmenuobj.style.top="-500px"

if (e.type=="click" && obj.visibility==hidden || e.type=="mouseover"){

if (this.enableswipe==1){

if (typeof this.swipetimer!="undefined")

clearTimeout(this.swipetimer)

obj.clip="rect(0 auto 0 0)"

this.bottomclip=0

this.swipeeffect()

}

obj.visibility="visible"

}

else if (e.type=="click")

obj.visibility="hidden"

},

iecompattest:function(){

return (document.compatMode && document.compatMode!="BackCompat")? document.documentElement : document.body

},

clearbrowseredge:function(obj, whichedge){

var edgeoffset=0

if (whichedge=="rightedge"){

var windowedge=this.ie && !window.opera? this.iecompattest().scrollLeft+this.iecompattest().clientWidth-15 : window.pageXOffset+window.innerWidth-15

this.dropmenuobj.contentmeasure=this.dropmenuobj.offsetWidth

if (windowedge-this.dropmenuobj.x < this.dropmenuobj.contentmeasure)

edgeoffset=this.dropmenuobj.contentmeasure-obj.offsetWidth

}

else{

var topedge=this.ie && !window.opera? this.iecompattest().scrollTop : window.pageYOffset

var windowedge=this.ie && !window.opera? this.iecompattest().scrollTop+this.iecompattest().clientHeight-15 : window.pageYOffset+window.innerHeight-18

this.dropmenuobj.contentmeasure=this.dropmenuobj.offsetHeight

if (windowedge-this.dropmenuobj.y < this.dropmenuobj.contentmeasure){

edgeoffset=this.dropmenuobj.contentmeasure+obj.offsetHeight

if ((this.dropmenuobj.y-topedge)<this.dropmenuobj.contentmeasure)

edgeoffset=this.dropmenuobj.y+obj.offsetHeight-topedge

}

}

return edgeoffset

},

dropit:function(obj, e, dropmenuID){

if (this.dropmenuobj!=null)

	this.dropmenuobj.style.visibility="hidden"

this.clearhidemenu()

if (this.ie||this.firefox){

obj.onmouseout=function(){cssdropdown.delayhidemenu()}

obj.onclick=function(){return !cssdropdown.disablemenuclick}

this.dropmenuobj=document.getElementById(dropmenuID)

if(!this.dropmenuobj) return;

this.dropmenuobj.onmouseover=function(){cssdropdown.clearhidemenu()}

this.dropmenuobj.onmouseout=function(e){cssdropdown.dynamichide(e)}

this.dropmenuobj.onclick=function(){cssdropdown.delayhidemenu()}

this.showhide(this.dropmenuobj.style, e)

this.dropmenuobj.x=this.getposOffset(obj, "left")

this.dropmenuobj.y=this.getposOffset(obj, "top")

this.dropmenuobj.style.left=this.dropmenuobj.x-this.clearbrowseredge(obj, "rightedge")+"px"

this.dropmenuobj.style.top=this.dropmenuobj.y-this.clearbrowseredge(obj, "bottomedge")+obj.offsetHeight+1+"px"

this.positionshim()

}

},

positionshim:function(){

if (this.enableiframeshim && typeof this.shimobject!="undefined"){

if (this.dropmenuobj.style.visibility=="visible"){

this.shimobject.style.width=this.dropmenuobj.offsetWidth+"px"

this.shimobject.style.height=this.dropmenuobj.offsetHeight+"px"

this.shimobject.style.left=this.dropmenuobj.style.left

this.shimobject.style.top=this.dropmenuobj.style.top

}

this.shimobject.style.display=(this.dropmenuobj.style.visibility=="visible")? "block" : "none"

}

},

hideshim:function(){

if (this.enableiframeshim && typeof this.shimobject!="undefined")

this.shimobject.style.display='none'

},

contains_firefox:function(a, b) {

while (b.parentNode)

if ((b = b.parentNode) == a)

return true;

return false;

},

dynamichide:function(e){

var evtobj=window.event? window.event : e

if (this.ie&&!this.dropmenuobj.contains(evtobj.toElement))

this.delayhidemenu()

else if (this.firefox&&e.currentTarget!= evtobj.relatedTarget&& !this.contains_firefox(evtobj.currentTarget, evtobj.relatedTarget))

this.delayhidemenu()

},

delayhidemenu:function(){

this.delayhide=setTimeout("cssdropdown.dropmenuobj.style.visibility='hidden'; cssdropdown.hideshim()",this.disappeardelay)

},

clearhidemenu:function(){

if (this.delayhide!="undefined")

clearTimeout(this.delayhide)

},

startchrome:function(){

for (var ids=0; ids<arguments.length; ids++){

var menuitems=document.getElementById(arguments[ids]).getElementsByTagName("a")

for (var i=0; i<menuitems.length; i++){

if (menuitems[i].getAttribute("rel")){

var relvalue=menuitems[i].getAttribute("rel")

menuitems[i].onmouseover=function(e){

var event=typeof e!="undefined"? e : window.event

cssdropdown.dropit(this,event,this.getAttribute("rel"))

}

}

}

}

if (window.createPopup && !window.XmlHttpRequest){

document.write('<IFRAME id="iframeshim"  src="" style="display: none; left: 0; top: 0; z-index: 90; position: absolute; filter: progid:DXImageTransform.Microsoft.Alpha(style=0,opacity=0)" frameBorder="0" scrolling="no"></IFRAME>')

this.shimobject=document.getElementById("iframeshim")

}

}

}

由上可以看出，var cssdropdown变量中有多个函数：

getposOffset:function(what, offsettype)

swipeeffect:function()

showhide:function(obj, e)

iecompattest:function()

clearbrowseredge:function(obj, whichedge)

dropit:function(obj, e, dropmenuID)

positionshim:function()

hideshim:function()

dynamichide:function(e)

delayhidemenu:function()

clearhidemenu:function()

startchrome:function()

2、然后，奇迹就出现了，跟新一下！会发现导航栏已经出现下拉菜单了，只是背景是透明的，原因是没有背景图片。是不是很简单呢？？

3、可是头疼的是，这个下拉菜单是透明的！咋么办？？

接着来你需要把DedeCMS5.7程序文件夹\dede\img里的mmenubg.gif(绿色背景图片，适用于绿色主题模板)或者DedeCMS5.5程 序文件夹\templets\images里的mmenubg.gif(蓝色背景图片，适用于蓝色主题模板)复制到DedeCMS5.6程序文件夹 /templets/default/images下面

现在你再看一下效果，呵呵，导航栏是不是已经出现熟悉的下拉菜单了：

4、此时，你想要的效果基本上已经完成了！如果你还想做其他的设置，比如调整位置，呵呵。。。只需要去/templets/default/style/dedecms.css

里你可以ctrl+f   寻找 .dropMenu 没错就是他控制着呢？

/*-------- 下拉菜单 --------------*/

.dropMenu {

	position:absolute;

	top: 0;

	z-index:100;

	width: 120px;

	visibility: hidden;

    filter: progid:DXImageTransform.Microsoft.Shadow(color=#CACACA, direction=135, strength=4);

	margin-top: -1px;

	border: 1px solid #93E1EB;

	border-top: 0px solid #3CA2DC;

	background-color: #FFF;

	background:url(../images/mmenubg.gif);

	padding-top:6px;

	padding-bottom:6px;

}

.dropMenu li {

	margin-top:2px;

	margin-bottom:4px;

	padding-left:6px;

}

.dropMenu a {

	width: auto;

	display: block;

	color: black;

	padding: 2px 0 2px 1.2em;

}

* html .dropMenu a {

	width: 100%;

}

.dropMenu a:hover {

	color:red;

	text-decoration: underline;

}

如果只是调整宽度，只用修改 ：

width: 100px;/*------ //原来参数是120-，如果二级标题字数少，还可以把参数调整到80，乃至是60--------*/

在此，就不多说了，如果看不懂，希望去学一学css的知识！

三、原理

1、

我们来看默认模板index.htm中有：

<!-- /flink -->

<div id="footAD" style="margin:10px auto; width:726px">{dede:myad name='indexfooterAD'/}</div>

{dede:include filename="footer.htm"/}

<!-- /footer -->

</body>

</html>

它其实就是链接到了footer.htm中，而在footer.htm的所有内容为：

<!-- //底部模板 -->

<div class="footer w960 center mt1 clear">

	<!--

		为了支持织梦团队的发展,请您保留织梦内容管理系统的链接信息.

		我们对支持织梦团队发展的朋友表示真心的感谢!织梦因您更精彩!

	-->

    <div class="footer_left"></div>

    <div class="footer_body">

	<p class="powered">

		Powered by <a href="http://www.dedecms.com" title="织梦内容管理系统(DedeCms)--国内最专业的PHP网站管理系统，轻松建站的首选利器。" target="_blank"><strong>DedeCMS_{dede:global.cfg_version/}</strong></a> © 2004-2011 <a href="http://www.desdev.cn/" target="_blank">DesDev</a> Inc.<br /><div class="copyright">{dede:global.cfg_powerby/}  {dede:global.cfg_beian/}</div></p>

<!-- /powered -->

   </div>

   <div class="footer_right"></div>

</div>

以上代码只是实现了：

2、

index如何引用到head.htm文件

在系统默认模板中的index.htm中有：

</head>

<body class="index">

{dede:include filename="head.htm"/}

<!-- /header -->

在我的模板中的index.htm中有：

</head>

<body class="index">

<div class="w960 center">

    <!-- /header -->

    {dede:include filename="head_i.htm"/}

    <!-- /header -->

另一模板是：

</HEAD>

<!-- header -->

<BODY class=index>{dede:include filename="head.htm"/}

<!-- /header -->

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