Setting the file. One moment.
Subchapter 8.3
RECIPES.mdMarkdown16 KBView on GitHub
Ready-to-build implementations for the cases that come up most in a React Native app. Start from the recipe, then adapt.
npx expo install react-native-reanimated react-native-worklets react-native-gesture-handler expo-haptics(react-native-keyboard-controller only for the keyboard recipe.) expo install, not npm install — it resolves the versions that match the SDK. The worklets Babel plugin is configured by babel-preset-expo automatically.
GestureHandlerRootView wraps the app once — in Expo Router, the root _layout:
import { GestureHandlerRootView } from 'react-native-gesture-handler';
export default function RootLayout() {
return (
<GestureHandlerRootView style={{ flex: 1 }}>
<Stack />
</GestureHandlerRootView>
);
}Imports and constants every recipe below shares:
import { useState, useEffect, useMemo } from 'react';
import Animated, {
useSharedValue, useAnimatedStyle, useAnimatedScrollHandler, useAnimatedReaction,
withSpring, withTiming, interpolate, Extrapolation, Easing,
FadeInDown, FadeOutDown, LinearTransition,
} from 'react-native-reanimated';
import { Gesture, GestureDetector } from 'react-native-gesture-handler';
import { scheduleOnRN } from 'react-native-worklets';
import * as Haptics from 'expo-haptics';
const EASE_OUT = Easing.bezier(0.23, 1, 0.32, 1); // strong ease-out for UI
const EASE_IN_OUT = Easing.bezier(0.77, 0, 0.175, 1); // on-screen movement
const EASE_SHEET = Easing.bezier(0.32, 0.72, 0, 1); // iOS sheet curveThree conventions, explained once here instead of in every recipe:
.get() / .set(), the form the Reanimated docs recommend for React Compiler support. .value still works, but the compiler can’t see through it.scheduleOnRN(fn, ...args) replaces the deprecated runOnJS(fn)(...args) for calling back to the React Native runtime from a worklet.useMemo. Rebuilding a gesture on every render can reattach the recognizer and drop a drag that’s mid-flight.Gesture Handler v3: Expo installs v2, and the recipes use its Gesture.Pan() builder. If the project is already on v3, the builder is legacy — each gesture is a hook taking one config object, with onStart → onActivate, onEnd → onDeactivate, and the success flag replaced by event.canceled (inverted). The hook manages its own identity, so drop the useMemo:
const pan = usePanGesture({
activeOffsetY: [-10, 10],
onActivate: () => { context.set(translateY.get()); },
onUpdate: (e) => { translateY.set(context.get() + e.translationY); },
onDeactivate: (e) => { /* settle with withSpring as below */ },
});Momentum projection decides where a flick was going, so a fast short swipe commits and a slow long one doesn’t. Rubber-banding makes a boundary resist instead of stopping dead.
// Where the finger would come to rest if it kept decelerating.
// Apple's exponential-decay form — not the v²/2a from physics class.
function project(velocity, decelerationRate = 0.998) {
'worklet';
return ((velocity / 1000) * decelerationRate) / (1 - decelerationRate);
}
// The further past the edge, the less the element follows.
function rubberband(overshoot, dimension, constant = 0.55) {
'worklet';
return (overshoot * dimension * constant) / (dimension + constant * Math.abs(overshoot));
}Every pressable in the app. This passes the frequency gate only because it’s near-imperceptible: 120ms and a 3% scale is the ceiling for something touched this often — anything longer or larger belongs to rarer moments, per step 1 in SKILL.md. No gesture, no shared value — a CSS transition is the whole implementation.
import Animated from 'react-native-reanimated';
import { Pressable, StyleSheet } from 'react-native';
function PressableScale({ onPress, children }) {
const [pressed, setPressed] = useState(false);
return (
<Pressable
onPress={onPress}
onPressIn={() => setPressed(true)}
onPressOut={() => setPressed(false)}
hitSlop={12}
pressRetentionOffset={16}
>
<Animated.View style={[styles.box, pressed && styles.pressed]}>{children}</Animated.View>
</Pressable>
);
}
const styles = StyleSheet.create({
box: {
transform: [{ scale: 1 }],
transitionProperty: 'transform',
transitionDuration: '120ms',
transitionTimingFunction: 'cubic-bezier(0.23, 1, 0.32, 1)',
},
pressed: { transform: [{ scale: 0.97 }] },
});setState is fine here — it fires twice per press, not per frame. hitSlop brings a small icon up to the 44pt target without growing it; pressRetentionOffset stops a slight finger drift from cancelling.
Before writing this: if the sheet is its own destination, use presentation: 'formSheet' (see Screen transitions) and get the platform’s real sheet for free. Build this only when the sheet has to live inside an existing screen.
const translateY = useSharedValue(0);
const context = useSharedValue(0);
const pan = useMemo(() => Gesture.Pan()
.activeOffsetY([-10, 10]) // let a horizontal swipe win; require intent before committing
.onStart(() => {
context.set(translateY.get()); // start from the current on-screen value, not from 0
})
.onUpdate((e) => {
const next = context.get() + e.translationY;
// downward is free; upward past the top resists
translateY.set(next >= 0 ? next : rubberband(next, HEIGHT));
})
.onEnd((e) => {
const projected = translateY.get() + project(e.velocityY);
if (projected > HEIGHT * 0.4) {
translateY.set(withSpring(HEIGHT, {
duration: 300, dampingRatio: 1, velocity: e.velocityY, overshootClamping: true,
}, (finished) => { if (finished) scheduleOnRN(onClose); }));
} else {
translateY.set(withSpring(0, { duration: 300, dampingRatio: 0.8, velocity: e.velocityY }));
scheduleOnRN(Haptics.impactAsync, Haptics.ImpactFeedbackStyle.Light); // it snapped home
}
}), [onClose]);
const sheetStyle = useAnimatedStyle(() => ({ transform: [{ translateY: translateY.get() }] }));The four details that separate this from a bad drag:
onStart captures the current value. Without it, grabbing a sheet mid-animation teleports it — the animation must continue from where the eye last saw it.project() means a quick flick dismisses even a few pixels down. Requiring 40% travel makes the sheet feel heavy.overshootClamping on dismissal — otherwise the sheet springs past the bottom of the screen and flashes a gap.The backdrop derives from the same value, so it’s always in sync and costs nothing:
const backdropStyle = useAnimatedStyle(() => ({
opacity: interpolate(translateY.get(), [0, HEIGHT], [1, 0], Extrapolation.CLAMP),
}));Before writing this: gesture-handler ships ReanimatedSwipeable (opens in a new tab), which already does swipe-to-reveal actions — thresholds, overshoot, open/close methods — on the UI thread. Reach for it when the row reveals action buttons. Build the gesture yourself only when the interaction is different in kind: swipe-to-commit with momentum projection, like this one.
const x = useSharedValue(0);
const context = useSharedValue(0);
const pan = useMemo(() => Gesture.Pan()
.activeOffsetX([-10, 10]) // must declare the axis, or it fights the vertical scroll
.onStart(() => { context.set(x.get()); }) // grab mid-spring continues from where the row is, not from 0
.onUpdate((e) => { x.set(Math.min(0, context.get() + e.translationX)); })
.onEnd((e) => {
const projected = x.get() + project(e.velocityX);
if (projected < -SWIPE_THRESHOLD) {
x.set(withTiming(-WIDTH, { duration: 200, easing: EASE_OUT }, (f) => {
if (f) scheduleOnRN(onDelete, id);
}));
} else {
x.set(withSpring(0, { duration: 300, dampingRatio: 1, velocity: e.velocityX }));
}
}), [onDelete, id]);Closing the gap the deleted row left is the list’s job, not the row’s:
const ROW_CLOSE = LinearTransition.duration(200); // module scope — builders rebuilt in render cost every re-render
<Animated.FlatList data={items} itemLayoutAnimation={ROW_CLOSE} ... />activeOffsetX is the mobile-specific part. A pan handler inside a scroll view with no axis declared will steal vertical scrolls, and the list will feel broken in a way that looks like a scrolling bug rather than a gesture bug.
const scrollY = useSharedValue(0);
const onScroll = useAnimatedScrollHandler((e) => { scrollY.set(e.contentOffset.y); });
const titleStyle = useAnimatedStyle(() => ({
opacity: interpolate(scrollY.get(), [0, 60], [1, 0], Extrapolation.CLAMP),
transform: [{ translateY: interpolate(scrollY.get(), [0, 60], [0, -12], Extrapolation.CLAMP) }],
}));
<Animated.ScrollView onScroll={onScroll} scrollEventThrottle={16}>Never animate the header’s height to collapse it. That runs a layout pass on the header and everything below it on every scroll frame — the one animation guaranteed to stutter, because it’s competing with the scroll itself. Give the container a fixed height and translate the content inside it, clipping with overflow: 'hidden'.
Extrapolation.CLAMP is not optional: without it, scrolling past 60 keeps driving opacity negative and the header reappears inverted at the bottom of a long list.
// The Reanimated docs recommend building layout animations outside components,
// or in useMemo — an inline chain in JSX rebuilds the builder on every render.
// A per-index delay can't live at module scope, so the row memoizes its own:
function Row({ item, index }) {
const entering = useMemo(() => FadeInDown.duration(250).delay(index * 40), [index]);
return <Animated.View entering={entering}>{/* ... */}</Animated.View>;
}
{items.map((item, i) => <Row key={item.id} item={item} index={i} />)}Stagger 30–80ms. Longer feels slow, shorter reads as simultaneous.
Never put entering on a row inside FlatList, FlashList, or any virtualized list. Rows are recycled, so the animation re-fires every time one scrolls back into view — the list appears to flicker while the user scrolls. Animate the list container once on mount, or use itemLayoutAnimation for reflow only.
Entrance animations are for content the user asked for and is waiting on. A list they scroll past all day should already be there.
Needs its own module and a one-time provider (Expo keyboard guide (opens in a new tab)):
npx expo install react-native-keyboard-controllerimport { KeyboardProvider } from 'react-native-keyboard-controller';
// Root _layout, next to GestureHandlerRootView — hooks below do nothing without it.
<KeyboardProvider>
<Stack />
</KeyboardProvider>import { useReanimatedKeyboardAnimation } from 'react-native-keyboard-controller';
const { height } = useReanimatedKeyboardAnimation(); // 0 → -keyboardHeight, on the UI thread
const footerStyle = useAnimatedStyle(() => ({ transform: [{ translateY: height.get() }] }));Never build this from Keyboard.addListener plus a timing animation. The keyboard rides a private system curve, the event arrives on the JS thread after the keyboard has already started moving, and any duration you pick will visibly lag or lead it. The UI must be driven by the keyboard’s actual position, frame by frame.
Measure once, then animate transforms.
const [layouts, setLayouts] = useState({}); // measured with onLayout, not per frame
const x = useSharedValue(0);
const w = useSharedValue(0);
useEffect(() => {
const l = layouts[active];
if (!l) return;
x.set(withTiming(l.x, { duration: 250, easing: EASE_IN_OUT }));
w.set(withTiming(l.width, { duration: 250, easing: EASE_IN_OUT }));
}, [active, layouts]);
const pillStyle = useAnimatedStyle(() => ({
transform: [{ translateX: x.get() }],
width: w.get(),
}));This is the sanctioned width animation: the pill is absolutely positioned with no children, so nothing else re-lays-out, and its corner radius survives — scaleX would smear the corners into ovals.
ease-in-out, because the pill is moving across the screen rather than entering or leaving it. Fire Haptics.selectionAsync() on the press, not when the pill lands.
Configure the native stack. Never rebuild a screen transition in JS: the native one runs on the platform side, keeps the interactive back gesture, and matches every other app on the device.
<Stack screenOptions={{ animation: reduced ? 'fade' : 'default' }}>
<Stack.Screen name="settings" options={{ animation: 'slide_from_right', animationMatchesGesture: true }} />
<Stack.Screen name="compose" options={{ presentation: 'modal' }} />
<Stack.Screen name="filter" options={{
presentation: 'formSheet',
sheetAllowedDetents: 'fitToContents',
sheetGrabberVisible: true,
}} />
</Stack>| Navigation | Option |
|---|---|
| Deeper into a hierarchy | animation: 'default' — the platform push, unmodified |
| A self-contained task the user can abandon | presentation: 'modal' |
| A short interruption: picker, filter, share | presentation: 'formSheet' with detents |
| Between tabs | animation: 'none' |
| Reduced motion | animation: 'fade' |
animationMatchesGesture: true makes the iOS back swipe run your transition in reverse under the finger, instead of the default push. Set it whenever you set a custom animation, or dragging back looks like a different app than pushing forward.
formSheet is native on both platforms, but not the same on both — the Expo modal docs (opens in a new tab) have the full list:
sheetAllowedDetents array works on iOS and silently truncates on Android — design for three.sheetGrabberVisible is iOS-only. Android shows no grabber; don’t rely on it as the only “this is draggable” affordance.presentation: 'modal' instead.fitToContents needs explicitly sized content. A flex: 1 root has no intrinsic height to fit — size the content, or the detent is wrong.// Module scope — layout-animation builders live outside the component.
const TOAST_ENTER = FadeInDown.duration(300).easing(EASE_OUT);
const TOAST_EXIT = FadeOutDown.duration(250).easing(EASE_OUT);
<Animated.View
entering={TOAST_ENTER}
exiting={TOAST_EXIT}
style={{ position: 'absolute', bottom: insets.bottom + 16, left: 16, right: 16 }}
/>bottom: 16 sits under the home indicator on every modern iPhone.If toasts stack and the list reflows, add itemLayoutAnimation and expect to tune the opacity against the reflow by eye — there’s no formula for that pair. Look at it again the next day.
When a crossing point matters — a detent, a snap, a pull-to-refresh arming — don’t poll it from JS and don’t scheduleOnRN every frame.
const armed = useSharedValue(false);
useAnimatedReaction(
() => pullDistance.get() > REFRESH_THRESHOLD,
(isArmed, wasArmed) => {
if (isArmed !== wasArmed) {
armed.set(isArmed);
scheduleOnRN(Haptics.impactAsync, Haptics.ImpactFeedbackStyle.Light);
}
}
);The comparison runs on the UI thread every frame; the JS call happens twice per pull. That’s the pattern for every “do something when the animation reaches X”.