react-native-scroll-interop

Native Android nested-scroll participation for React Native.

React Native scroll sources already own touch handling, source position, fling physics, and velocity integration. Native Android UI that reacts to the same gesture should participate in that existing transaction, not infer a second one from JavaScript events.

Preserve the physics. Preserve the motion.

Don't synchronize scrolling. Participate in it.

react-native-scroll-interop lets native Android participants join the real synchronous nested-scroll transaction produced by a supported React Native scroll source. React Native remains the single owner of source motion.

React Native scroll source
          │
          ▼
real Android nested-scroll transaction
          │
          ▼
 PRE → React Native child → POST
          │
          ▼
 N native participants

one React Native scroll physics
one synchronous Android nested-scroll transaction
N native participants

Material3 TopAppBar and FloatingToolbar are shipped reference participants used to make the primitive observable. They are not the purpose of the package and are not part of the neutral transport contract.

Reference demo

The clip makes native participation observable through the shipped TopAppBar and FloatingToolbar reference consumers. React Native still owns the gesture, source position, and fling physics. Select the preview for the higher-quality MP4.

Status

react-native-scroll-interop@0.1.0-alpha.1
npm dist-tag: next

This alpha has a deliberately narrow compatibility matrix. Recorded evidence and the current publication gates are tracked separately in docs/release.md.

Negative guarantees

The transport has:

• no second source Scroller / OverScroller;
• no parent scrollBy / scrollTo on the React Native source;
• no sampled scrollY transport;
• no timer-based momentum reconstruction;
• no duplicated velocity integration;
• no per-frame JavaScript transport.

These are architecture invariants guarded by the repository checks, not performance slogans.

Architecture

The library tracks source identity and lifecycle, conserves signed PRE/POST distance, and exposes the same Android transaction to native participants:

requested = preConsumed + childConsumed + postConsumed + remaining

Full contract: docs/architecture.md.

Installation

npm install react-native-scroll-interop@next

The package autolinks as a standard React Native Android package. Expo Modules are not required by the native runtime.

Compatibility

Target	Current status
Expo SDK 57 + React Native 0.86.0	Recorded PR #26 baseline: exact tarball install, clean prebuild, Android compile/assemble, install/runtime, navigation ownership, touch/fling/reverse-fling
bare React Native 0.87.0-rc.3	Recorded PR #26 baseline: exact tarball install, standard autolinking, compatibility adapter, Android compile/assemble/install, Hermes runtime, touch/fling/reverse-fling
React Native 0.87.x	Accepted by the peer range; the repository example builds, but stable 0.87 runtime certification is not yet recorded
react-native-screens 4.26.x	Version-scoped navigation ownership adapter validated on the recorded baseline
Android	Neutral nested-scroll core + generic RN boundary + shipped Material3 reference participants
iOS / web	NativeScrollHost preserves normal View layout, Material reference chrome renders no UI, and navigation options pass through; Android nested-scroll semantics are not emulated

Peer contracts:

react-native                       >=0.86.0 <0.87.0 || >=0.87.0-rc.3 <0.88.0
react                              >=19.2.0 <20.0.0
react-native-safe-area-context     >=5.0.0 <6.0.0
react-native-screens               >=4.26.0 <4.27.0    optional
expo-router                        >=57.0.0 <58.0.0     optional
@react-navigation/native-stack     >=7.0.0 <8.0.0       optional

The recorded baseline is evidence for those exact consumer shapes, not a blanket certification of every version admitted by the peer ranges. See docs/release.md.

Verified source boundary

The current Android boundary recognizes React Native's ReactScrollView and generated ReactNestedScrollView. Recorded runtime validation uses ScrollView-based Expo and bare examples.

This alpha does not claim verified support for FlatList, FlashList, LegendList, or arbitrary virtualized-list implementations. The architecture can admit additional React Native sources through compatible native source boundaries, but each boundary still requires explicit validation.

Examples

Repository-only consumer apps live under examples/:

• examples/expo — Expo SDK 57 / React Native 0.86 app using the config plugin and Expo Router integration.
• examples/bare — bare React Native 0.87 app using standard autolinking, the bare compatibility adapter, NativeScrollHost, and MaterialTopAppBar.

The Expo app is the visual reference demo: Material3 TopAppBar and FloatingToolbar make native participation visible, but they do not define the purpose of the package. The stable RN 0.87 example keeps the integration path reproducible; the formal release certification above remains the recorded 0.87.0-rc.3 gate until the stable line is rerun and documented. Neither example nor any demo media is shipped in the npm tarball.

Root API

The root export contains the ownership host plus the currently shipped Material3 reference participants. It is not intended as a general Material3 component surface.

import {
  MaterialToolbar,
  MaterialTopAppBar,
  NativeScrollHost,
} from 'react-native-scroll-interop';

NativeScrollHost

Use NativeScrollHost when the source is not already owned by a supported native screen/container integration.

import { ScrollView } from 'react-native';
import { NativeScrollHost } from 'react-native-scroll-interop';

<NativeScrollHost style={{ flex: 1 }}>
  <ScrollView>{/* content */}</ScrollView>
</NativeScrollHost>

It discovers a supported RN vertical source and delegates real Android parent callbacks to the generic RN controller. It does not own source motion.

MaterialTopAppBar

<MaterialTopAppBar
  title="Home"
  variant="large"
  scrollBehavior="exitUntilCollapsed"
/>

Key props:

title: string
visible?: boolean
variant?: 'small' | 'medium' | 'large'
scrollBehavior?: 'none' | 'pinned' | 'enterAlways' | 'exitUntilCollapsed'
navigationIcon?: 'none' | 'back'
navigationAccessibilityLabel?: string
onNavigationPress?: () => void
placement?: 'overlay' | 'header'
themeMode?: 'system' | 'light' | 'dark'
dynamicColor?: boolean

The TopAppBar is a native Material3 PRE/POST consumer. It never moves the RN source directly. pinned, enterAlways, and exitUntilCollapsed map one-to-one to the Material3 scroll behaviors. none keeps the bar fixed without attaching Material scroll state; unlike pinned, it does not track content overlap. Navigation defaults to pinned for small bars and exitUntilCollapsed for every expandable variant.

MaterialToolbar

MaterialToolbar.Root
MaterialToolbar.Content
MaterialToolbar.LeadingContent
MaterialToolbar.TrailingContent
MaterialToolbar.IconButton
MaterialToolbar.TextButton
MaterialToolbar.Icon
MaterialToolbar.Text
MaterialToolbar.Fab

scrollBehavior="exitAlways" observes child-consumed POST distance. FloatingToolbar consumes zero source motion.

Bare React Native

node ./node_modules/react-native-scroll-interop/plugin/bareReactNativeScrollCompat.js

The compatibility adapter is version-scoped to the validated RN 0.86/0.87 source shapes and fails closed on unsupported shapes. The bare example runs this automatically from its postinstall script.

Expo config plugin

{
  "expo": {
    "plugins": [
      [
        "react-native-scroll-interop",
        {
          "android": {
            "reactNativeScrollCompat": true,
            "reactNativeScreensInterop": true
          }
        }
      ]
    ]
  }
}

reactNativeScrollCompat applies the same version-scoped RN source compatibility path used by bare RN. reactNativeScreensInterop enables the validated screens 4.26.x navigation-first ownership path.

react-native-screens

The current adapter keeps the native screen/container as the real nested-scroll ancestor and delegates through ReactNativeScreenNestedScrollBridge. The screen-side integration contains no Material3, Expo Router, or React Navigation behavior.

Upstream-neutral design and migration plan: docs/react-native-screens.md.

Independent upstream work

Two open upstream changes move responsibilities to the layers that already own them:

1. React Native #57972 preserves the AndroidX TYPE_NON_TOUCH nested-scroll lifecycle for ordinary ReactNestedScrollView flings while React Native continues to initiate and own the fling.
2. react-native-screens #4537 exposes a neutral Android nested-scroll delegate seam while screens retains ownership and first priority.

They solve different upstream responsibilities. Neither is a blocker for 0.1.0-alpha.1; the alpha uses narrow, fail-closed compatibility adapters for its currently validated versions.

Expo Router

import { Stack } from 'react-native-scroll-interop/router';

<Stack>
  <Stack.Screen
    name="index"
    options={{
      title: 'Home',
      headerLargeTitle: true,
      material3: {
        topAppBar: { scrollBehavior: 'exitUntilCollapsed' },
      },
    }}
  />
</Stack>

The adapter wraps Expo Router's existing Stack. It does not create navigation state or transport scroll frames.

React Navigation

import {
  material3NativeStackNavigatorOptions,
  material3NativeStackScreenOptions,
  withMaterial3NativeStackOptions,
} from 'react-native-scroll-interop/react-navigation';

<Stack.Navigator
  screenOptions={material3NativeStackNavigatorOptions({
    headerLargeTitle: true,
    material3: {
      topAppBar: { scrollBehavior: 'exitUntilCollapsed' },
    },
  })}
>
  {/* screens */}
</Stack.Navigator>

Expo Router and React Navigation share one internal navigator-neutral mapper and Material3 header renderer. Neither adapter owns nested-scroll transport.

Validation

npm run check
npm pack --dry-run
npm publish --dry-run --access public --tag next

The check suite guards architecture boundaries, nested-scroll ownership/conservation, Material3 boundaries, navigation mapping, RN compatibility transformations, the current screens adapter, repository example layout, and npm package surface.

Native/runtime changes additionally require fresh consumer builds and device/emulator validation. See docs/release.md.

Project docs

• Architecture
• Release / certification
• Roadmap
• react-native-screens upstream path
• Examples
• Changelog

Stability

0.1.x-alpha is pre-1.0 and uses the next dist-tag. The stable latest tag should wait for stable RN certification, reproducible regression coverage, a settled navigation ownership path, and real external usage.

License

MIT.