用jQuery和CSS构建下拉菜单

六

2009

发布者: seasun

研究表明，导航栏吸引了大多数浏览者的注意力。在存在下拉菜单的导航栏中，具有良好的组织及直观的印象是最关键的，优美的设计在开发中也至关重要。在本教程中，我会告诉您如来来创建一个缓慢下沉的漂亮的下拉菜单：

下拉菜单 demo

第一步：HTML文档

首先为你的导航创建一个无序列表，然后简单的写一下另外一个无序列表作为导航子菜单

定义导航样式

ul.topnav {
list-style: none;
padding: 0 20px;
margin: 0;
float: left;
width: 920px;
background: #222;
font-size: 1.2em;
background: url(topnav_bg.gif) repeat-x;
}
ul.topnav li {
float: left;
margin: 0;
padding: 0 15px 0 0;
position: relative; /*–Declare X and Y axis base for sub navigation–*/
}
ul.topnav li a{
padding: 10px 5px;
color: #fff;
display: block;
text-decoration: none;
float: left;
}
ul.topnav li a:hover{
background: url(topnav_hover.gif) no-repeat center top;
}
ul.topnav li span { /*–Drop down trigger styles–*/
width: 17px;
height: 35px;
float: left;
background: url(subnav_btn.gif) no-repeat center top;
}
ul.topnav li span.subhover {background-position: center bottombottom; cursor: pointer;} /*–Hover effect for trigger–*/
ul.topnav li ul.subnav {
list-style: none;
position: absolute; /*–Important – Keeps subnav from affecting main navigation flow–*/
left: 0; top: 35px;
background: #333;
margin: 0; padding: 0;
display: none;
float: left;
width: 170px;
border: 1px solid #111;
}
ul.topnav li ul.subnav li{
margin: 0; padding: 0;
border-top: 1px solid #252525; /*–Create bevel effect–*/
border-bottom: 1px solid #444; /*–Create bevel effect–*/
clear: both;
width: 170px;
}
html ul.topnav li ul.subnav li a {
float: left;
width: 145px;
background: #333 url(dropdown_linkbg.gif) no-repeat 10px center;
padding-left: 20px;
}
html ul.topnav li ul.subnav li a:hover { /*–Hover effect for subnav links–*/
background: #222 url(dropdown_linkbg.gif) no-repeat 10px center;
}

如果您是jQuery新手，那么请先阅读这里的教程。

下面包含注释的脚本会告诉您jQuery是如何来表现的。

$(document).ready(function(){
$(“ul.subnav”).parent().append(“<span></span>”); //Only shows drop down trigger when js is enabled (Adds empty span tag after ul.subnav*)
$(“ul.topnav li span”).click(function() { //When trigger is clicked…
//Following events are applied to the subnav itself (moving subnav up and down)
$(this).parent().find(“ul.subnav”).slideDown(‘fast’).show(); //Drop down the subnav on click
$(this).parent().hover(function() {
}, function(){
$(this).parent().find(“ul.subnav”).slideUp(‘slow’); //When the mouse hovers out of the subnav, move it back up
});
//Following events are applied to the trigger (Hover events for the trigger)
}).hover(function() {
$(this).addClass(“subhover”); //On hover over, add class “subhover”
}, function(){ //On Hover Out
$(this).removeClass(“subhover”); //On hover out, remove class “subhover”
});
});