expo-native-ui

Imported from AhmadAbdelaziz8/cash-splitter-v2 (app/.agents/skills/expo-native-ui/SKILL.md). Install upstream with npx skills add AhmadAbdelaziz8/cash-splitter-v2 --skill expo-native-ui. Copyright stays with the author (MIT).

Expo Native UI Guidelines

For routes, links, stacks, tabs, modals, sheets, and headers, use the expo-router skill. For any motion — entering/exiting, gestures, springs, keyboard-driven UI — use the expo-animation skill.

Before picking any UI component, check expo-ui first. @expo/ui provides native equivalents — BottomSheet, Button, Picker, Slider, Menu, Section, Switch, SegmentedControl, and more — rendered as real SwiftUI on iOS and Jetpack Compose on Android, available in Expo Go on SDK 56+ with no custom build. Load the expo-ui skill to find the right component before falling back to React Native built-ins or community libraries. This skill (expo-native-ui) covers the surrounding structure: Expo Router navigation, layout, styling, and visual effects.

References

Consult these resources as needed:

references/
  controls.md            Native iOS: Switch, Slider, SegmentedControl, DateTimePicker, Picker
  gradients.md           CSS gradients via experimental_backgroundImage (New Arch only)
  icons.md               SF Symbols via expo-symbols SymbolView: names, weights, animations; Material icons on Android
  media.md               Camera, audio, video, and file saving
  storage.md             SQLite, AsyncStorage, SecureStore
  visual-effects.md      Blur (expo-blur) and liquid glass (expo-glass-effect)
  webgpu-three.md        3D graphics, games, GPU visualizations with WebGPU and Three.js

Running the App

CRITICAL: Always try Expo Go first before creating custom builds.

Most Expo apps work in Expo Go without any custom native code. Before running npx expo run:ios or npx expo run:android:

1. Start with Expo Go: Run npx expo start and scan the QR code with Expo Go
2. Check if features work: Test your app thoroughly in Expo Go
3. Only create custom builds when required - see below

When Custom Builds Are Required

You need npx expo run:ios/android or eas build ONLY when using:

• Local Expo modules (custom native code in modules/)
• Apple targets (widgets, app clips, extensions via @bacons/apple-targets)
• Third-party native modules not included in Expo Go
• Custom native configuration that can't be expressed in app.json

When Expo Go Works

Expo Go supports a wide range of features out of the box:

• Most expo-* packages (camera, location, sensors, sqlite, etc.) — but not all: remote push notifications don't work in Expo Go on Android since SDK 53, and some packages need native capabilities Expo Go doesn't bundle (e.g. WebGPU — see references/webgpu-three.md)
• Expo Router navigation and deep links
• Most UI libraries (reanimated, gesture handler, etc.)

If you're unsure, try Expo Go first. Creating custom builds adds complexity, slower iteration, and requires Xcode/Android Studio setup.

Code Style

• Be cautious of unterminated strings. Ensure nested backticks are escaped; never forget to escape quotes correctly.
• Always use import statements at the top of the file.
• Always use kebab-case for file names, e.g. comment-card.tsx
• Never use special characters in file names
• Configure tsconfig.json with path aliases, and prefer aliases over relative imports for refactors.

Library Preferences

• For any sheet, picker, slider, toggle, menu, or grouped-form section: use @expo/ui (see expo-ui skill) before reaching for a React Native built-in or community library — it renders native SwiftUI/Compose and works in Expo Go on SDK 56+. For grouped/settings-style rows (short, fixed-length), use @expo/ui's List + ListItem. For large or unknown-length scrolling lists (feeds, search results, catalogs), use FlatList or FlashList — @expo/ui's List is not virtualized.
• Never use modules removed from React Native such as Picker, WebView, SafeAreaView, or AsyncStorage
• Never use legacy expo-permissions
• expo-audio not expo-av
• expo-video not expo-av
• expo-symbols (SymbolView) for SF Symbols on iOS, not @expo/vector-icons — see references/icons.md. SF Symbols are Apple-only: on Android every icon needs a Material source (md prop on NativeTabs triggers; in-screen options under "Android: Material Icons" in icons.md), never SF-only iconography
• react-native-safe-area-context not react-native SafeAreaView
• process.env.EXPO_OS not Platform.OS
• React.use not React.useContext
• expo-image Image component instead of intrinsic element img
• expo-glass-effect for liquid glass backdrops
• Color from expo-router for native semantic colors, not raw PlatformColor (type-safe, auto-adapts to light/dark)
• In SDK 56+, never import from @react-navigation/* directly — use expo-router/react-navigation instead (covers @react-navigation/native, /core, /elements, /routers)

Responsiveness

• Wrap screens with scrollable content in a ScrollView. Screens whose root is a FlatList/FlashList must not add an outer ScrollView (the list is the scroll container), and full-bleed screens (camera, map, canvas) need neither
• Use <ScrollView contentInsetAdjustmentBehavior="automatic" /> instead of <SafeAreaView> for smarter safe area insets
• contentInsetAdjustmentBehavior="automatic" should be applied to FlatList and SectionList as well
• Use flexbox instead of Dimensions API
• ALWAYS prefer useWindowDimensions over Dimensions.get() to measure screen size

Behavior

• Use expo-haptics conditionally on iOS to make more delightful experiences
• Use views with built-in haptics like <Switch /> from React Native and @react-native-community/datetimepicker
• When a Stack route has scrollable content, make the ScrollView (or FlatList) the first component inside the route, with contentInsetAdjustmentBehavior="automatic" set
• Use the <Text selectable /> prop on text containing data that could be copied
• Consider formatting large numbers like 1.4M or 38k
• Never use intrinsic elements like 'img' or 'div' unless in a webview or Expo DOM component
• Every screen that loads data has four states (loading, error, empty, content) - never show the empty state while the first load is still resolving; the rules live in the expo-data-fetching skill
• On scrollable forms and search results, use keyboardShouldPersistTaps="handled" so controls receive the first tap and unhandled taps can dismiss the keyboard. Use "always" only when unhandled taps should also keep it open
• A form's primary action must never sit under the keyboard. For UI that tracks the keyboard's real frame, load the expo-animation skill's keyboard recipe (react-native-keyboard-controller) - never Keyboard.addListener plus a timing animation
• Every enabled control must perform its advertised action: search filters results, Save commits edits, and settings affect behavior. Empty handlers and success alerts are not implementations; local state is enough when the user requested a prototype
• For async saves, preserve drafts and handle pending/failure states per expo-data-fetching; do not dismiss a form before its save succeeds

Before calling a screen complete, walk through its primary task, including one failure and recovery when it loads or saves data. Check keyboard access and back/dismiss behavior. Try long titles, missing images, no search results, and large system text; required actions must remain reachable. Report what you exercised and what you could not run.

Styling

Follow each platform's own design language: Apple Human Interface Guidelines on iOS, Material Design 3 on Android. Never dress one platform in the other's uniform - no FAB or ripple in iOS layouts; no hand-built iOS chrome (back-chevrons, large-title text, iOS-styled switches) on Android.

General Styling Rules

• Prefer flex gap over margin and padding styles
• Prefer padding over margin where possible
• Always account for safe area, either with stack headers, tabs, or ScrollView/FlatList contentInsetAdjustmentBehavior="automatic"
• Ensure both top and bottom safe area insets are accounted for
• Inline styles not StyleSheet.create unless reusing styles is faster
• For any motion or animation work, load the expo-animation skill — it owns the animate-or-not decision, timing values, and interruption rules
• Use { borderCurve: 'continuous' } for rounded corners unless creating a capsule shape
• ALWAYS use a navigation stack title instead of a custom text element on the page
• When padding a ScrollView, use contentContainerStyle padding and gap instead of padding on the ScrollView itself (reduces clipping)
• CSS and Tailwind are not supported - use inline styles

Colors

Use the Color API from expo-router for native semantic colors. It is a type-safe wrapper over PlatformColor that exposes iOS UIKit colors through Color.ios.* and Android Material 3 colors through Color.android.material.* (static) or Color.android.dynamic.* (adapts to the user's wallpaper on Android 12+). These resolve on-device and automatically adapt to light/dark mode and accessibility settings, so you no longer maintain separate light/dark hex tables or a colors.web.ts file.

Color is platform-specific, so wrap each value in Platform.select with a default hex fallback for web. Centralize the palette in theme/colors.ts and import colors everywhere:

// theme/colors.ts
import { Platform } from "react-native";
import { Color } from "expo-router";

export const colors = {
  label: Platform.select({
    ios: Color.ios.label,
    android: Color.android.dynamic.onSurface,
    default: "#000000",
  })!,
  secondaryLabel: Platform.select({
    ios: Color.ios.secondaryLabel,
    android: Color.android.dynamic.onSurfaceVariant,
    default: "#3c3c43",
  })!,
  separator: Platform.select({
    ios: Color.ios.separator,
    android: Color.android.dynamic.outlineVariant,
    default: "#c6c6c8",
  })!,
  systemBackground: Platform.select({
    ios: Color.ios.systemBackground,
    android: Color.android.dynamic.surface,
    default: "#ffffff",
  })!,
  secondarySystemBackground: Platform.select({
    ios: Color.ios.secondarySystemBackground,
    android: Color.android.dynamic.surfaceVariant,
    default: "#f2f2f7",
  })!,
  systemBlue: Platform.select({
    ios: Color.ios.systemBlue,
    android: Color.android.dynamic.primary,
    default: "#007aff",
  })!,
};

import { colors } from "@/theme/colors";

<View style={{ backgroundColor: colors.systemBackground }}>
  <Text style={{ color: colors.label }}>Title</Text>
</View>;

• iOS re-resolves these colors automatically when the system theme changes. On Android, call useColorScheme() inside any component that renders them so it re-renders when the theme flips (required when React Compiler memoizes the component).
• Don't pass Color / PlatformColor values into Reanimated styles — they are opaque native color objects, not strings; use static colors there.
• Platform.select({...})! returns string | OpaqueColorValue. Most React Native style props accept ColorValue (string | OpaqueColorValue) so this works fine. But some third-party props only accept string (e.g. tintColor on expo-image). Cast when needed: colors.label as string.

Text Styling

• Add the selectable prop to every <Text/> element displaying important data or error messages
• Counters should use { fontVariant: 'tabular-nums' } for alignment

Shadows

Use CSS boxShadow style prop. NEVER use legacy React Native shadow or elevation styles.

<View style={{ boxShadow: "0 1px 2px rgba(0, 0, 0, 0.05)" }} />

'inset' shadows are supported.

Submitting Feedback

If you encounter errors, misleading or outdated information in this skill, report it so Expo can improve:

npx --yes submit-expo-feedback@latest --category skills --subject "expo-native-ui" "<actionable feedback>"

Only submit when you have something specific and actionable to report. Include as much relevant context as possible. If an AI agent repeatedly failed or the user had to take over an Expo task, load the expo-skill-feedback skill and follow its eval-candidate flow instead of reusing the command above.