128 lines
2.9 KiB
Markdown
128 lines
2.9 KiB
Markdown
---
|
||
id: 587d78a8367417b2b2512ae7
|
||
title: 使用关键字更改动画定时器
|
||
challengeType: 0
|
||
videoUrl: 'https://scrimba.com/c/cJKvwCM'
|
||
forumTopicId: 301045
|
||
dashedName: change-animation-timing-with-keywords
|
||
---
|
||
|
||
# --description--
|
||
|
||
在 CSS 动画里，`animation-timing-function` 用来定义动画的速度曲线。 速度曲线决定了动画从一套 CSS 样式变为另一套所用的时间。 如果要描述的动画是一辆车在指定时间内（`animation-duration`）从 A 运动到 B，那么 `animation-timing-function` 表述的就是车在运动中的加速和减速等过程。
|
||
|
||
有一些预定义的关键字可用于常见的选项。 比如，默认值是 `ease`，动画以低速开始，然后加快，在结束前变慢。 其它常用的值包括 `ease-out`：动画以高速开始，以低速结束；`ease-in`，动画以低速开始，以高速结束；`linear`：动画从头到尾的速度是相同的。
|
||
|
||
# --instructions--
|
||
|
||
给 id 为 `ball1` 和 `ball2` 的元素添加 `animation-timing-function`，`ball1` 的属性值为 `linear`，`ball2` 的属性值为 `ease-out`。 它们的 `animation-duration` 都为 2 秒，注意观察它们在开始和结束时的不同。
|
||
|
||
# --hints--
|
||
|
||
id 为 `ball1` 的元素的 `animation-timing-function` 属性值应为 `linear`。
|
||
|
||
```js
|
||
const ball1Animation = __helpers.removeWhiteSpace(
|
||
$('#ball1').css('animation-timing-function')
|
||
);
|
||
assert(ball1Animation == 'linear' || ball1Animation == 'cubic-bezier(0,0,1,1)');
|
||
```
|
||
|
||
id 为 `ball2` 的元素的 `animation-timing-function` 属性值为 `ease-out`。
|
||
|
||
```js
|
||
const ball2Animation = __helpers.removeWhiteSpace(
|
||
$('#ball2').css('animation-timing-function')
|
||
);
|
||
assert(
|
||
ball2Animation == 'ease-out' || ball2Animation == 'cubic-bezier(0,0,0.58,1)'
|
||
);
|
||
```
|
||
|
||
# --seed--
|
||
|
||
## --seed-contents--
|
||
|
||
```html
|
||
<style>
|
||
|
||
.balls {
|
||
border-radius: 50%;
|
||
background: linear-gradient(
|
||
35deg,
|
||
#ccffff,
|
||
#ffcccc
|
||
);
|
||
position: fixed;
|
||
width: 50px;
|
||
height: 50px;
|
||
margin-top: 50px;
|
||
animation-name: bounce;
|
||
animation-duration: 2s;
|
||
animation-iteration-count: infinite;
|
||
}
|
||
#ball1 {
|
||
left:27%;
|
||
|
||
}
|
||
#ball2 {
|
||
left:56%;
|
||
|
||
}
|
||
|
||
@keyframes bounce {
|
||
0% {
|
||
top: 0px;
|
||
}
|
||
100% {
|
||
top: 249px;
|
||
}
|
||
}
|
||
|
||
</style>
|
||
|
||
<div class="balls" id="ball1"></div>
|
||
<div class="balls" id="ball2"></div>
|
||
```
|
||
|
||
# --solutions--
|
||
|
||
```html
|
||
<style>
|
||
.balls {
|
||
border-radius: 50%;
|
||
background: linear-gradient(
|
||
35deg,
|
||
#ccffff,
|
||
#ffcccc
|
||
);
|
||
position: fixed;
|
||
width: 50px;
|
||
height: 50px;
|
||
margin-top: 50px;
|
||
animation-name: bounce;
|
||
animation-duration: 2s;
|
||
animation-iteration-count: infinite;
|
||
}
|
||
#ball1 {
|
||
left:27%;
|
||
animation-timing-function: linear;
|
||
}
|
||
#ball2 {
|
||
left:56%;
|
||
animation-timing-function: ease-out;
|
||
}
|
||
|
||
@keyframes bounce {
|
||
0% {
|
||
top: 0px;
|
||
}
|
||
100% {
|
||
top: 249px;
|
||
}
|
||
}
|
||
</style>
|
||
<div class="balls" id="ball1"></div>
|
||
<div class="balls" id="ball2"></div>
|
||
```
|