animation

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since September 2015.

尝试一下

语法

css
/* @keyframes duration | easing-function | delay |
iteration-count | direction | fill-mode | play-state | name */
animation: 3s ease-in 1s 2 reverse both paused slidein;

/* @keyframes duration | easing-function | delay | name */
animation: 3s linear 1s slidein;

/* two animations */
animation:
  3s linear slidein,
  3s ease-out 5s slideout;

animation 属性用来指定一组或多组动画,每组之间用逗号相隔。

每组动画规定的属性如下:

每个动画定义中的属性值的顺序很重要:可以被解析为 <time> 的第一个值被分配给animation-duration,第二个分配给 animation-delay

每个动画定义中的值的顺序,对于区分 animation-name 值与其他关键字也很重要。解析时,对于除 animation-name 之外的有效的关键字,必须被前面的简写中没有找到值的属性所接受。此外,在序列化时,animation-name 与以及其他属性值做区分等情况下,必须输出其他属性的默认值。

Values

<single-animation-iteration-count>

动画播放的次数。该值必须是animation-iteration-count可用的值之一。

<single-animation-direction>

动画播放的方向。该值必须是animation-direction可用的值之一。

<single-animation-fill-mode>

确定动画在执行之前和之后这两个阶段应用的样式。该值必须是animation-fill-mode可用的值之一。

<single-animation-play-state>

确定动画是否正在播放。该值必须是animation-play-state中可用的值之一。

语法

animation = 
<single-animation>#

<single-animation> =
<time [0s,∞]> ||
<easing-function> ||
<time> ||
<single-animation-iteration-count> ||
<single-animation-direction> ||
<single-animation-fill-mode> ||
<single-animation-play-state> ||
[ none | <keyframes-name> ]

<easing-function> =
<linear-easing-function> |
<cubic-bezier-easing-function> |
<step-easing-function>

<single-animation-iteration-count> =
infinite |
<number [0,∞]>

<single-animation-direction> =
normal |
reverse |
alternate |
alternate-reverse

<single-animation-fill-mode> =
none |
forwards |
backwards |
both

<single-animation-play-state> =
running |
paused

<keyframes-name> =
<custom-ident> |
<string>

<linear-easing-function> =
linear |
<linear()>

<cubic-bezier-easing-function> =
ease |
ease-in |
ease-out |
ease-in-out |
<cubic-bezier()>

<step-easing-function> =
step-start |
step-end |
<steps()>

<linear()> =
linear( [ <number> && <percentage>{0,2} ]# )

<cubic-bezier()> =
cubic-bezier( [ <number [0,1]> , <number> ]#{2} )

<steps()> =
steps( <integer> , <step-position>? )

<step-position> =
jump-start |
jump-end |
jump-none |
jump-both |
start |
end

示例

赛隆人之眼

html
<div class="view_port">
  <div class="polling_message">Listening for dispatches</div>
  <div class="cylon_eye"></div>
</div>
css
.polling_message {
  color: white;
  float: left;
  margin-right: 2%;
}

.view_port {
  background-color: black;
  height: 25px;
  width: 100%;
  overflow: hidden;
}

.cylon_eye {
  background-color: red;
  background-image: linear-gradient(
    to right,
    rgba(0, 0, 0, 0.9) 25%,
    rgba(0, 0, 0, 0.1) 50%,
    rgba(0, 0, 0, 0.9) 75%
  );
  color: white;
  height: 100%;
  width: 20%;

  -webkit-animation: 4s linear 0s infinite alternate move_eye;
  animation: 4s linear 0s infinite alternate move_eye;
}

@-webkit-keyframes move_eye {
  from {
    margin-left: -20%;
  }
  to {
    margin-left: 100%;
  }
}
@keyframes move_eye {
  from {
    margin-left: -20%;
  }
  to {
    margin-left: 100%;
  }
}

更多示例请参阅使用 CSS 动画

潜在的问题

眨眼和闪烁的动画对于有认知问题的人来说是有问题的,比如注意力缺陷多动障碍 (ADHD)。此外,某些动画效果可以触发前庭神经紊乱、癫痫、偏头痛和暗点敏感性。

考虑提供一种暂停或禁用动画的机制,以及使用 Reduced Motion Media Query(简约运动媒体查询),为那些表示不喜欢动画的用户创建一个良好的体验。

规范

Specification
CSS Animations Level 1
# animation

浏览器兼容性

BCD tables only load in the browser

参见