@keyframes在CSS中用於創(chuàng)建關(guān)鍵幀動畫，允許開發(fā)者定義元素在動畫不同階段的樣式。 1. 通過百分比或from/to指定動畫各個(gè)階段的樣式，如0%、50%、100%分別表示開始、中間和結(jié)束狀態(tài)；2. 使用animation屬性將定義好的關(guān)鍵幀動畫應(yīng)用到元素上，包括設(shè)置動畫名稱、持續(xù)時(shí)間、速度函數(shù)、延遲和播放次數(shù)等；3. 常用於實(shí)現(xiàn)複雜的自定義動畫效果，如加載指示器、懸停效果、UI反饋和背景動畫；4. 注意事項(xiàng)包括確保包含起始和結(jié)束幀、避免動畫引起佈局抖動、測試瀏覽器兼容性以及使用animation-fill-mode控制動畫結(jié)束後元素的樣式。

A CSS animation using @keyframes is a way to define how an element should look at specific points during an animation. Unlike simple transitions, which go from one state to another, keyframe animations let you control each step of the motion — like making something move, fade, or change color gradually over time.

What Does @keyframes Do Exactly?

You use @keyframes to create a set of styles that happen at different stages of the animation. These stages are usually expressed as percentages:

• 0% means the start of the animation
• 50% means halfway through
• 100% means the end

You can also use from and to instead of 0% and 100% , but most people stick with percentages for more control.

For example:

 @keyframes slide {
  0% {
    transform: translateX(0);
  }
  50% {
    transform: translateX(100px);
  }
  100% {
    transform: translateX(0);
  }
}

This defines a basic back-and-forth movement.

How to Use @keyframes in Your CSS

Once you've defined your animation with @keyframes , you need to apply it to an element using the animation property (or individual sub-properties).

Here's a minimal example:

 .slide-box {
  width: 100px;
  height: 100px;
  background: blue;
  animation-name: slide;
  animation-duration: 2s;
  animation-timing-function: linear;
  animation-delay: 0s;
  animation-iteration-count: infinite;
}

Or you can shorten it using the shorthand:

 .slide-box {
  animation: slide 2s linear infinite;
}

Some common properties:

• animation-name : refers to the name given in @keyframes
• animation-duration : how long one cycle takes
• animation-timing-function : controls speed curve (like linear , ease-in-out )
• animation-delay : how long to wait before starting
• animation-iteration-count : how many times it plays ( infinite loops forever)

When Should You Use Keyframe Animations?

They're especially useful when you want smooth, custom effects that aren't possible with just transitions. For instance:

• Loading spinners or progress indicators
• Hover effects that animate multiple properties
• Complex UI feedback (like buttons bouncing on click)
• Background animations or parallax effects

Also, because they're built into CSS, they perform well on modern browsers without needing JavaScript.

Keep in mind:

• Too many animations can distract users or slow down performance.
• Always test on mobile devices where resources might be limited.
• Use them to enhance, not replace, functional design.

A Few Things to Watch Out For

There are some small gotchas when working with @keyframes . For example:

• If you forget to include 0% or 100% , the browser may not animate smoothly.
• Animating layout properties like width , height , or margin can cause layout thrashing — consider using transform instead.
• Browser support is solid these days, but always double-check if you're targeting older platforms.

One detail people often miss is that if you don't specify animation-fill-mode , the element will snap back to its original style after the animation ends. Adding animation-fill-mode: forwards keeps it at the last frame's style.

So, putting it all together, @keyframes gives you precise control over how elements behave during an animation. It's not hard to set up once you understand the basics, but it does require attention to timing and structure. Basically, it's a powerful tool once you get the hang of it.

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