这里先解说下——这里有A /B 两个按钮，分别链接a/b.css， 只要单击按钮就可以实现改变头部id为change_css 的css文件。当你希望change_css一开始没有css只是点击按钮的时候才有css的话，那么你给change_css这个id的链接 href=“ ”
<html>
<head>
<meta http-equiv="Content-Type" content="text/htmlcharset=utf-8" />
<link id="change_css" rel="stylesheet" type="text/css" href="a.css">
</head>
<body>
<input type=button value="A按钮" onclick="document.all.change_css.href='a.css'">
<input type=button value="B按钮" onclick="document.all.change_css.href='b.css'">
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<title>css模拟手机安装图标效果</title>
<meta charset="UTF-8">
<style>
*{/*外层margin,padding设置0*/
margin:0
padding:0
}
#abox{/*外层大容器相对定位，宽度高度各100px*/
position:relative
width:100px
height:100px
margin-left:100px
margin-top:100px
}
#abox::after{/*伪元素设置安装中字样，绑定动画myfirst3，安装完毕后安装中字样消失*/
content:""
display:block
width:100%
position:absolute
color:white
bottom:0
left:0
text-align:center
font-size:14px
font-weight:bold
animation:myfirst3 10s
-webkit-animation:myfirst3 10s/* Safari and Chrome */
}
@keyframes myfirst3/*安装中文字动画*/
{
from {
content:"安装中"
}
to {
content:""
}
}
#box1{/*底层图片，被透明的黑色层遮住*/
position:relative
width:100px
height:100px
background:url("123.png")
background-size:100% 100%
}
#box1::after{/*设置一个伪元素，让其绑定一个动画，透明度在动画完毕后变得完全透明*/
content:""
display:block
position:absolute
width:100%
height:100%
top:0
left:0
animation:myfirst2 10s
-webkit-animation:myfirst2 10s/* Safari and Chrome */
}
@keyframes myfirst2
{
from {
background:black
filter:alpha(Opacity=60)
-moz-opacity:0.6
opacity:0.6
}
to {
background:none
filter:alpha(Opacity=0)
-moz-opacity:0
opacity:0
}
}
#box2{/*黑色层容器，绝对定位*/
position:absolute
width:60px
height:60px
top:20px
left:20px
overflow:hidden
border-radius:50%
}
#box2 img{/*插入一张图片，让其可以覆盖背景图片，且显示出效果*/
width:100px
height:100px
margin-top:-20px
margin-left:-20px
}
#box3{/*扇形黑色容器变化容器，注意控制left和top让其居中*/
position:absolute
width:46px
height:46px
left:7px
top:7px
border-radius:50%
animation:myfirst 3s/*绑定扇形变化动画效果*/
-webkit-animation:myfirst 3s/* Safari and Chrome */
}
@keyframes myfirst/*扇形黑色容器变化动画,利用css的裁剪功能模拟扇形变化*/
{
0%{
clip-path: polygon(50% 50%, 68% 0, 100% 0, 100% 100%, 0 100%, 0 0, 52% 0)
filter:alpha(Opacity=60)
-moz-opacity:0.6
opacity:0.6
background:black
}
10%{
clip-path: polygon(50% 50%, 100% 26%, 100% 45%, 100% 100%, 0 100%, 0 0, 52% 0)
filter:alpha(Opacity=60)
-moz-opacity:0.6
opacity:0.6
background:black
}
20%{
clip-path: polygon(50% 50%, 100% 71%, 100% 86%, 100% 100%, 0 100%, 0 0, 52% 0)
filter:alpha(Opacity=60)
-moz-opacity:0.6
opacity:0.6
background:black
}
30%{
clip-path: polygon(50% 50%, 100% 100%, 58% 100%, 34% 100%, 0 100%, 0 0, 52% 0)
filter:alpha(Opacity=60)
-moz-opacity:0.6
opacity:0.6
background:black
}
40%{
clip-path: polygon(50% 50%, 59% 100%, 7% 100%, 0 100%, 0 74%, 0 0, 52% 0)
filter:alpha(Opacity=60)
-moz-opacity:0.6
opacity:0.6
background:black
}
50%{
clip-path: polygon(50% 50%, 19% 100%, 0 100%, 0 58%, 0 35%, 0 0, 52% 0)
filter:alpha(Opacity=60)
-moz-opacity:0.6
opacity:0.6
background:black
}
60%{
clip-path: polygon(50% 50%, 0 78%, 0 51%, 0 29%, 0 18%, 0 0, 52% 0)
filter:alpha(Opacity=60)
-moz-opacity:0.6
opacity:0.6
background:black
}
70%{
clip-path: polygon(50% 50%, 0 40%, 0 27%, 0 13%, 0 0, 28% 0, 52% 0)
filter:alpha(Opacity=60)
-moz-opacity:0.6
opacity:0.6
background:black
}
80%{
clip-path: polygon(50% 50%, 0 11%, 0 0, 13% 0, 25% 0, 38% 0, 52% 0)
filter:alpha(Opacity=60)
-moz-opacity:0.6
opacity:0.6
background:black
}
90%{
clip-path: polygon(50% 50%, 7% 0, 15% 0, 23% 0, 32% 0, 41% 0, 52% 0)
filter:alpha(Opacity=60)
-moz-opacity:0.6
opacity:0.6
background:black
}
100%{
clip-path: polygon(50% 50%, 52% 0, 52% 0, 52% 0, 51% 0, 52% 0, 52% 0)
filter:alpha(Opacity=0)
-moz-opacity:0
opacity:0
background:none
}
}
</style>
</head>
<body>
<div id="abox"><!--外层容器-->
<div id="box1"></div><!---第一层背景容器-->
<div id="box2"><!--第二层图片容器-->
<div id="box3"></div>
<img src="123.png">
</div>
</div>
</body>
</html>
