mobile-react-native-reanimated

name	mobile-react-native-reanimated
description	Imported TRAE skill from mobile/React_Native_Reanimated.md Use when this capability is needed.
metadata	{"author":"Ditto190"}

Skill: React Native Reanimated

Purpose

To create high-performance, smooth (60fps+) animations and interactions in React Native by running animation logic on the UI thread.

When to Use

• When Animated API from React Native is too slow or stutters.
• For complex gestures (drag, pinch, swipe).
• For shared element transitions.

Procedure

1. Setup

1. Install:

   npm install react-native-reanimated
   

2. Babel Plugin: Add react-native-reanimated/plugin to babel.config.js (must be listed last).

   plugins: [
     // other plugins...
     'react-native-reanimated/plugin',
   ],
   

3. Clear Cache: npx expo start -c.

2. Basic Animation (Shared Values)

1. Define Value: Use useSharedValue.

   const width = useSharedValue(100);
   

2. Define Style: Use useAnimatedStyle.

   const animatedStyle = useAnimatedStyle(() => {
     return { width: width.value };
   });
   

3. Render: Use Animated.View.

   <Animated.View style={[styles.box, animatedStyle]} />
   

4. Trigger: Update value with utility functions.

   width.value = withSpring(200);
   // or withTiming(200, { duration: 500 })
   

3. Gestures

Combine with react-native-gesture-handler.

• Use GestureDetector to modify shared values based on touch events.

Constraints

• UI Thread Only: You cannot run complex JS logic inside useAnimatedStyle (unless using runOnJS).
• Debugging: Errors on the UI thread can be harder to trace; use console.log carefully or runOnJS for debugging.

Expected Output

Fluid animations that do not block the Javascript thread, providing a "native" feel.

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Source: Ditto190/crispy-nextjs-turborepo-monorepo — distributed by TomeVault.