@keyframes 规则
要创建 CSS 动画，您首先需要了解 @keyframes 规则，@keyframes 规则用来定义动画各个阶段的属性值，类似于 flash 动画中的关键帧，语法格式如下：
@keyframes animationName {
from {
properties: value;
}
percentage {
properties: value;
}
to {
properties: value;
}
}
// 或者
@keyframes animationName {
0% {
properties: value;
}
percentage {
properties: value;
}
100% {
properties: value;
}
}
下面我们来看一个简单的 @keyframes 规则示例：
@keyframes ball {
0% { top: 0px; left: 0px;}
25% { top: 0px; left: 350px;}
50% { top: 200px; left: 350px;}
75% { top: 200px; left: 0px;}
100% { top: 0px; left: 0px;}
}
下面就来详细介绍一下上述属性的使用：
<!DOCTYPE html>
<html>
<head>
<style>
@keyframes ball {
0% { top: 0px; left: 0px;}
25% { top: 0px; left: 350px;}
50% { top: 200px; left: 350px;}
75% { top: 200px; left: 0px;}
100% { top: 0px; left: 0px;}
}
div {
width: 100px;
height: 100px;
border-radius: 50%;
border: 3px solid black;
position: relative;
animation-name: ball;
}
</style>
</head>
<body>
<div></div>
</body>
</html>
注意：要想让动画成功播放，您还需要定义 animation-duration 属性，否则会因为 animation-duration 属性的默认值为 0，导致动画并不会播放。
<!DOCTYPE html>
<html>
<head>
<style>
@keyframes ball {
0% { top: 0px; left: 0px;}
25% { top: 0px; left: 350px;}
50% { top: 200px; left: 350px;}
75% { top: 200px; left: 0px;}
100% { top: 0px; left: 0px;}
}
div {
width: 100px;
height: 100px;
border-radius: 50%;
border: 3px solid black;
position: relative;
animation-name: ball;
animation-duration: 2s;
}
</style>
</head>
<body>
<div></div>
</body>
</html>
提示：动画若想成功播放，必须要定义 animation-name 和 animation-duration 属性。
<!DOCTYPE html>
<html>
<head>
<style>
@keyframes ball {
0% {left: 0px;}
50% {left: 350px;}
100% {left: 0px;}
}
div {
width: 100px;
height: 100px;
border-radius: 50%;
border: 3px solid black;
text-align: center;
line-height: 100px;
position: relative;
animation-name: ball;
animation-duration: 2s;
}
.one {
animation-timing-function: ease;
}
.two {
animation-timing-function: ease-in;
}
.three {
animation-timing-function: ease-out;
}
.four {
animation-timing-function: ease-in-out;
}
</style>
</head>
<body>
<div class="one">ease</div>
<div class="two">ease-in</div>
<div class="three">ease-out</div>
<div class="four">ease-in-out</div>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<style>
@keyframes box {
0% {transform: rotate(0);}
50% {transform: rotate(0.5turn);}
100% {transform: rotate(1turn);}
}
div {
width: 100px;
height: 100px;
border-radius: 50%;
float: left;
border: 3px solid black;
text-align: center;
line-height: 100px;
position: relative;
animation-name: box;
animation-duration: 2s;
animation-iteration-count: 1;
animation-fill-mode: forwards;
}
</style>
</head>
<body>
<div>forwards</div>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<style>
@keyframes ball {
0% {left: 0px;}
50% {left: 350px;}
100% {left: 0px;}
}
div {
width: 100px;
height: 100px;
border-radius: 50%;
border: 3px solid black;
text-align: center;
line-height: 100px;
position: relative;
animation-name: ball;
animation-duration: 2s;
}
.one {
animation-delay: 0.5s;
}
.two {
animation-delay: -0.5s;
}
</style>
</head>
<body>
<div class="one">0.5s</div>
<div class="two">-0.5s</div>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<style>
@keyframes box {
0% {transform: rotate(0);}
50% {transform: rotate(0.5turn);}
100% {transform: rotate(1turn);}
}
div {
width: 100px;
height: 100px;
float: left;
border: 3px solid black;
text-align: center;
line-height: 100px;
position: relative;
animation-name: box;
animation-duration: 2s;
}
.one {
animation-iteration-count: 1;
}
.two {
margin-left: 50px;
animation-iteration-count: infinite;
}
</style>
</head>
<body>
<div class="one">1</div>
<div class="two">infinite</div>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<style>
@keyframes box {
0% {transform: rotate(0);}
50% {transform: rotate(0.5turn);}
100% {transform: rotate(1turn);}
}
div {
width: 100px;
height: 100px;
float: left;
border: 3px solid black;
text-align: center;
line-height: 100px;
position: relative;
animation-name: box;
animation-duration: 2s;
animation-iteration-count: infinite;
}
.one {
animation-direction: reverse;
}
.two {
margin-left: 50px;
animation-direction: alternate;
}
</style>
</head>
<body>
<div class="one">reverse</div>
<div class="two">alternate</div>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<style>
@keyframes box {
0% {transform: rotate(0);}
50% {transform: rotate(0.5turn);}
100% {transform: rotate(1turn);}
}
div {
width: 100px;
height: 100px;
float: left;
border: 3px solid black;
text-align: center;
line-height: 100px;
position: relative;
animation-name: box;
animation-duration: 2s;
animation-iteration-count: infinite;
}
.one {
animation-play-state: running;
}
.two {
margin-left: 50px;
animation-play-state: paused;
}
</style>
</head>
<body>
<div class="one">running</div>
<div class="two">paused</div>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<style>
@keyframes box {
0% {transform: rotate(0);}
50% {transform: rotate(0.5turn);}
100% {transform: rotate(1turn);}
}
div {
width: 100px;
height: 100px;
border-radius: 50%;
float: left;
border: 3px solid black;
text-align: center;
line-height: 100px;
position: relative;
animation: box 2s linear 0s infinite alternate;
}
</style>
</head>
<body>
<div>animation</div>
</body>
</html>