motion-ui

动效系统 v4.2

Production-ready UI motion system for React / Next.js.

Focused on performance, accessibility, and usability — not decoration.

何时使用

Use this motion system when motion:

• Guides attention (e.g., onboarding, key actions)
• Communicates state (loading, success, error, transitions)
• Preserves spatial continuity (layout changes, navigation)

Appropriate Scenarios

• Interactive components (buttons, modals, menus)
• State transitions (loading → loaded, open → closed)
• Navigation and layout continuity (shared elements, crossfade)

Considerations

• Accessibility: Always support reduced motion
• Device adaptation: Adjust for low-end devices
• Performance trade-offs: Prefer responsiveness over visual smoothness

Avoid Using Motion When

• It is purely decorative
• It reduces usability or clarity
• It impacts performance negatively

---

工作原理

核心原则

Motion must:

• Guide attention
• Communicate state
• Preserve spatial continuity

If it does none → remove it.

---

安装

npm install motion

---

版本

• motion/react - default for current Motion for React projects (package: motion)
• framer-motion - legacy import path for projects that still depend on Framer Motion

Do not mix. Mixing causes conflicting internal schedulers and broken AnimatePresence contexts — components from one package will not coordinate exit animations with components from the other.

To check which version your project uses:

cat package.json | grep -E '"motion"|"framer-motion"'

Always import from one source consistently:

// Correct (modern)
import { motion, AnimatePresence } from "motion/react"

// Correct (legacy)
import { motion, AnimatePresence } from "framer-motion"

// Never mix both in the same project

---

动效令牌

// motionTokens.ts
export const motionTokens = {
  duration: {
    fast: 0.18,
    normal: 0.35,
    slow: 0.6
  },
  // Use these as the `ease` value inside a `transition` object:
  // transition={{ duration: motionTokens.duration.normal, ease: motionTokens.easing.smooth }}
  easing: {
    smooth: [0.22, 1, 0.36, 1] as [number, number, number, number],
    sharp:  [0.4,  0, 0.2, 1] as [number, number, number, number]
  },
  distance: {
    sm: 8,
    md: 16,
    lg: 24
  }
}

Usage example:

import { motionTokens } from "@/lib/motionTokens"

<motion.div
  initial={{ opacity: 0, y: motionTokens.distance.md }}
  animate={{ opacity: 1, y: 0 }}
  transition={{
    duration: motionTokens.duration.normal,
    ease: motionTokens.easing.smooth
  }}
/>

---

性能规则

Safe

• transform
• opacity

Avoid

• width / height
• top / left

Rule: responsiveness > smoothness

---

设备适配

The heuristic combines CPU core count and available memory for a more reliable signal. deviceMemory is available on Chrome/Android; the fallback covers Safari and Firefox.

const isLowEnd =
  typeof navigator !== "undefined" && (
    // Low memory (Chrome/Android only; undefined elsewhere → treat as capable)
    (navigator.deviceMemory !== undefined && navigator.deviceMemory <= 2) ||
    // Few cores AND no memory API (covers Safari/Firefox on weak hardware)
    (navigator.deviceMemory === undefined && navigator.hardwareConcurrency <= 4)
  )

const duration = isLowEnd ? 0.2 : 0.4

---

可访问性

JS (useReducedMotion)

import { motion, useReducedMotion } from "motion/react"

export function FadeIn() {
  const reduce = useReducedMotion()

  return (
    <motion.div
      initial={{ opacity: 0, y: reduce ? 0 : 24 }}
      animate={{ opacity: 1, y: 0 }}
    />
  )
}

CSS

@media (prefers-reduced-motion: reduce) {
  .motion-safe-transition {
    transition: opacity 0.2s;
  }

  .motion-reduce-transform {
    transform: none !important;
  }
}

Tailwind

<div class="motion-safe:animate-fade motion-reduce:opacity-100"></div>

---

架构与模式

核心模式

Scenario	Pattern
Hover feedback	whileHover
Tap / press feedback	whileTap
Reveal on scroll	whileInView
Scroll-linked value	useScroll + useTransform
Conditional mount/unmount	AnimatePresence
Small layout shifts (single element, < ~300px change)	layout prop
Large layout shifts or full-page reflows	Avoid layout; use CSS transitions or page-level routing instead
Complex, imperative sequences	useAnimate

Why avoid layout on large containers? Framer's layout animation uses transform to reconcile positions, but on elements that span the full viewport or trigger deep reflow, the measurement cost causes visible jank and CLS. Prefer CSS Grid/Flexbox transitions or coordinate with layoutId on specific child elements only.

布局与过渡

• Shared element transitions → layoutId (must be unique per mounted instance)
• Enter / exit transitions → AnimatePresence (see mode guidance below)

AnimatePresence mode

Always specify mode explicitly — the default ("sync") runs enter and exit simultaneously, which causes visual overlap in most UI patterns.

mode	When to use
"wait"	Exit completes before enter starts. Use for modals, toasts, page transitions.
"sync" (default)	Enter and exit overlap. Use only when overlap is intentional (e.g., crossfade carousels).
"popLayout"	Exiting element is popped out of flow immediately; remaining items animate to fill. Use for lists, tabs, dismissible cards.

// Modal — always use "wait"
<AnimatePresence mode="wait">
  {open && <Modal key="modal" />}
</AnimatePresence>

// Dismissible list item — use "popLayout"
<AnimatePresence mode="popLayout">
  {items.map(item => <Card key={item.id} />)}
</AnimatePresence>

---

高级模式（概念）

• Parallax (scroll-linked transforms)
• Scroll storytelling (sticky sections)
• 3D tilt (pointer-based transforms)
• Crossfade (shared layoutId)
• Progressive reveal (clip-path)
• Skeleton loading (looped opacity)
• Micro-interactions (hover/tap feedback)
• Spring system (physics-based motion)

---

模态框要点

• Focus trap
• Escape close
• Scroll lock
• ARIA roles
• Use AnimatePresence mode="wait" so exit animation completes before the next modal enters

Full Example

import React, { useEffect, useRef, useState } from "react"
import { motion, AnimatePresence } from "motion/react"

function useFocusTrap(ref: React.RefObject<HTMLDivElement | null>, active: boolean) {
  useEffect(() => {
    if (!active || !ref.current) return
    const el = ref.current
    const focusable = el.querySelectorAll<HTMLElement>(
      'button, [href], input, select, textarea, [tabindex]:not([tabindex="-1"])'
    )
    const first = focusable[0]
    const last  = focusable[focusable.length - 1]

    function handleKey(e: KeyboardEvent) {
      if (e.key !== "Tab") return
      if (e.shiftKey && document.activeElement === first) {
        e.preventDefault()
        last?.focus()
      } else if (!e.shiftKey && document.activeElement === last) {
        e.preventDefault()
        first?.focus()
      }
    }

    el.addEventListener("keydown", handleKey)
    first?.focus()
    return () => el.removeEventListener("keydown", handleKey)
  }, [active, ref])
}

function useScrollLock(active: boolean) {
  useEffect(() => {
    if (!active) return
    const prev = document.body.style.overflow
    document.body.style.overflow = "hidden"
    return () => { document.body.style.overflow = prev }
  }, [active])
}

function Modal({ open, closeModal }: { open: boolean; closeModal: () => void }) {
  const ref = useRef<HTMLDivElement>(null)

  useFocusTrap(ref, open)
  useScrollLock(open)

  useEffect(() => {
    function onKey(e: KeyboardEvent) {
      if (e.key === "Escape") closeModal()
    }
    if (open) window.addEventListener("keydown", onKey)
    return () => window.removeEventListener("keydown", onKey)
  }, [open, closeModal])

  return (
    // mode="wait" ensures exit animation finishes before any new modal enters
    <AnimatePresence mode="wait">
      {open && (
        <motion.div
          role="dialog"
          aria-modal="true"
          aria-labelledby="modal-title"
          initial={{ opacity: 0 }}
          animate={{ opacity: 1 }}
          exit={{ opacity: 0 }}
          transition={{ duration: 0.2 }}
          className="fixed inset-0 flex items-center justify-center bg-black/40"
        >
          <motion.div
            ref={ref}
            initial={{ scale: 0.95, opacity: 0 }}
            animate={{ scale: 1,    opacity: 1 }}
            exit={{    scale: 0.95, opacity: 0 }}
            transition={{ duration: 0.2, ease: [0.22, 1, 0.36, 1] }}
            className="bg-white p-6 rounded"
          >
            <h2 id="modal-title">Dialog Title</h2>
            <button onClick={closeModal}>Close</button>
          </motion.div>
        </motion.div>
      )}
    </AnimatePresence>
  )
}

export function Example() {
  const [open, setOpen] = useState(false)

  return (
    <>
      <button onClick={() => setOpen(true)}>Open</button>
      <Modal open={open} closeModal={() => setOpen(false)} />
    </>
  )
}

---

SSR 安全

• Match initial states between server and client renders
• Avoid implicit animation origins (always set initial explicitly)
• Wrap motion components in "use client" in Next.js App Router

---

调试

Check:

• Wrong import (mixing motion/react and framer-motion)
• Missing "use client" directive in Next.js App Router
• Missing key prop on AnimatePresence children
• Hydration mismatch (initial state differs between SSR and client)
• layout prop misuse on large containers causing reflow jank
• State-driven animation not triggering (check dependency arrays)

---

质量保证

• No CLS
• Keyboard works
• Focus trapped in modals
• ARIA roles correct (role="dialog", aria-modal="true")
• Reduced motion respected (useReducedMotion + CSS media query)
• No hydration warnings in Next.js
• Animations stop cleanly on unmount (no memory leaks)
• AnimatePresence mode set explicitly on all usage sites

---

反模式

• Animating layout properties (width, height, top, left)
• Infinite animations without purpose (always ask: what state does this communicate?)
• Over-staggering lists (keep staggerChildren ≤ 0.1s; beyond that it feels slow)
• Ignoring reduced motion preferences
• Using layout on large or full-viewport containers
• Omitting mode on AnimatePresence (default "sync" causes visual overlap)
• Using motion purely for decoration

---

哲学

Motion is interaction design.

---

最终规则

If motion does not improve UX → remove it.

---

示例

Button Interaction

import { motion } from "motion/react"

export function Button() {
  return (
    <motion.button
      whileHover={{ scale: 1.02 }}
      whileTap={{ scale: 0.97 }}
      transition={{ duration: 0.15, ease: [0.4, 0, 0.2, 1] }}
    >
      Click me
    </motion.button>
  )
}

---

Reduced Motion Example

import { motion, useReducedMotion } from "motion/react"

export function FadeIn() {
  const reduce = useReducedMotion()

  return (
    <motion.div
      initial={{ opacity: 0, y: reduce ? 0 : 24 }}
      animate={{ opacity: 1, y: 0 }}
      transition={{ duration: reduce ? 0.1 : 0.35, ease: [0.22, 1, 0.36, 1] }}
    />
  )
}

---

Stagger List

import { motion } from "motion/react"

const container = {
  hidden: {},
  visible: {
    transition: { staggerChildren: 0.08 } // keep ≤ 0.1s to avoid sluggishness
  }
}

const item = {
  hidden:  { opacity: 0, y: 10 },
  visible: { opacity: 1, y: 0,  transition: { duration: 0.3, ease: [0.22, 1, 0.36, 1] } }
}

export function List() {
  return (
    <motion.ul variants={container} initial="hidden" animate="visible">
      {[1, 2, 3].map(i => (
        <motion.li key={i} variants={item}>Item {i}</motion.li>
      ))}
    </motion.ul>
  )
}

---

Modal with AnimatePresence

import { motion, AnimatePresence } from "motion/react"

export function Modal({ open }: { open: boolean }) {
  return (
    <AnimatePresence mode="wait">
      {open && (
        <motion.div
          initial={{ opacity: 0, scale: 0.95 }}
          animate={{ opacity: 1, scale: 1    }}
          exit={{    opacity: 0, scale: 0.95 }}
          transition={{ duration: 0.2, ease: [0.22, 1, 0.36, 1] }}
        />
      )}
    </AnimatePresence>
  )
}

---

Scroll Parallax

import { useScroll, useTransform, motion } from "motion/react"

export function Parallax() {
  const { scrollYProgress } = useScroll()
  const y = useTransform(scrollYProgress, [0, 1], [0, -80])

  return <motion.div style={{ y }} />
}

---

Skeleton Loading

import { motion } from "motion/react"

export function Skeleton() {
  return (
    <motion.div
      className="bg-gray-200 h-6 w-full rounded"
      animate={{ opacity: [0.5, 1, 0.5] }}
      transition={{
        duration: 1.5,       // comfortable pulse — was missing, caused fast flash
        repeat: Infinity,
        ease: "easeInOut"
      }}
    />
  )
}

---

Shared Layout (Crossfade)

import { motion } from "motion/react"

// layoutId must be unique per mounted instance.
// If multiple instances can exist simultaneously, append a unique id:
// layoutId={`shared-${item.id}`}
export function Shared() {
  return <motion.div layoutId="shared" />
}