react-native-patterns（React native 模式）

React Native Patterns

Overview

Patterns for building maintainable React Native components. Covers touch interactions (Pressable), list rendering (FlashList), modal patterns (bottom sheets), accessibility, navigation, and RN-specific requirements that differ from web React.

For React web patterns (hooks, context, composition), see the react-patterns skill.

Workflows

Building an interactive screen:

1. Set up SafeAreaView or apply safe area insets
2. Use Pressable for all interactive elements (44pt minimum)
3. Add haptic feedback on primary actions
4. Use FlashList for lists, ScrollView for fixed content
5. Implement bottom sheet for detail/modal views
6. Add accessibility labels to all interactive elements
7. Test on device for touch targets and scroll performance

Guidance

Pressable (not TouchableOpacity)

Pressable is the standard touch component. TouchableOpacity is deprecated.

Key principles:

• 44pt minimum touch target on all interactive elements
• Use hitSlop to expand touch area beyond visual bounds: hitSlop={{top: 8, bottom: 8, left: 8, right: 8}}
• Style feedback via style function: style={({pressed}) => [pressed && {opacity: 0.7}]}
• Or use NativeWind: className="active:opacity-70"
• Add haptics on press for primary actions: onPress={() => {Haptics.impactAsync(); doAction();}}

Text-Only Strings Rule

React Native requires all visible text to be wrapped in <Text>:

✅ <View><Text>Hello</Text></View>
❌ <View>Hello</View>  // Crashes at runtime

This applies to conditional renders, string interpolation, and JSX expressions. Always wrap strings in Text.

ScrollView Patterns

Two className targets:

• className — outer container (flex, background)
• contentContainerClassName — inner content (padding, gap, alignment)

Use ScrollView for screens with fixed, non-dynamic content. Use FlashList for dynamic lists.

showsVerticalScrollIndicator={false} for cleaner visual when custom scroll indicators are used.

FlashList Patterns

High-performance list rendering:

• estimatedItemSize is required — estimate average item height in points
• renderItem receives {item, index} — keep render function pure
• keyExtractor — use unique string ID from data
• contentContainerClassName — NativeWind styling for inner content
• ItemSeparatorComponent — consistent spacing between items
• ListEmptyComponent — graceful empty state

Bottom Sheet as Modal

@gorhom/bottom-sheet replaces web modal dialogs:

• Define snapPoints array: ['25%', '50%', '90%']
• Use BottomSheetModal with BottomSheetModalProvider for imperative control
• BottomSheetScrollView for scrollable sheet content
• BottomSheetBackdrop for press-to-dismiss overlay
• Present: bottomSheetRef.current?.present()
• Dismiss: bottomSheetRef.current?.dismiss()

expo-image Patterns

Use for all image display:

• Remote images: source={{uri: 'https://...'}}
• Local images: source={require('../assets/image.png')}
• Blurhash placeholder: placeholder="LKO2?U%2Tw=w]~RBVZRi}" for loading state
• contentFit="cover" for card thumbnails, "contain" for full images
• transition={300} for smooth fade-in on load

Accessibility

Required accessibility props for interactive elements:

Guidelines:

• All Pressable elements need accessibilityLabel
• Images need accessibilityLabel describing content
• Use accessibilityRole="header" for screen titles
• Toggle/checkbox: set accessibilityState={{checked: isChecked}}
• Disabled elements: accessibilityState={{disabled: true}}

Chat-Forward Component Patterns

Demos use a chat-forward interface where the conversation thread is the primary UI.

Chat Screen Layout

Three zones:

• Header: Minimal — title, back nav, optional status. Uses safe area top inset.
• Message stream: FlashList or inverted ScrollView for the conversation. Agent and user messages alternate. Rich content is embedded within agent message components.
• Input bar: Text input pinned to bottom. Uses KeyboardAvoidingView (iOS) or android:windowSoftInputMode="adjustResize". Safe area bottom inset for home indicator. Optional quick-action chips above the text field.

Message Bubble

Agent and user bubbles have distinct styling (alignment, color, shape):

• Agent bubble: Left-aligned, neutral background, can contain child components (cards, summaries, action buttons)
• User bubble: Right-aligned, accent background, text only
• Bubbles animate in with FadeInDown.duration(300) on append

Inline Rich Card

Compact data card rendered as a child of an agent message bubble:

• Photo thumbnail (expo-image) + title + key metric + status badge
• Tappable — opens bottom sheet with full detail
• For card sets: horizontal ScrollView within the message, or vertical stack
• Stagger animation: FadeInDown.delay(index * 50).duration(300)

Summary Card

Running totals/status that updates as the conversation progresses:

• Shows aggregated state: Keep ($X), Sell ($Y), Donate ($Z), Progress (N%)
• Can be rendered as a sticky element above the input bar for persistent visibility
• Content crossfades on update (150ms timing)

Prompt Card

Agent suggestion with embedded action buttons:

• Text prompt + 1-3 action buttons inline
• Buttons are Pressable with 44pt targets, haptic on press
• After tap, the prompt card updates to show the confirmed action
• E.g., *"Want me to find pickup options?"* → [Yes] [Not now]

Comparison View

Before/after or side-by-side content within a message:

• Two expo-image instances with labels (Before / After)
• Optional delta annotation (e.g., "New scratch detected")

Timeline View

Chronological event list rendered inline within an agent message:

• Compact: date + title + icon per event
• Expandable: tap to show detail (inline expand or bottom sheet)
• Vertical line connector between events

Notification Message

Proactive agent alert that appears as a new message in the thread:

• Distinctive styling (icon + emphasis color) to differentiate from regular agent messages
• Can contain inline action buttons
• E.g., *"Storm season starts in 6 weeks. Your basement still shows moisture risk."*

Navigation from Components

Use Expo Router's useRouter() hook:

• router.push('/path') — navigate forward (adds to stack)
• router.replace('/path') — replace current screen
• router.back() — go back
• router.canGoBack() — check if back navigation possible
• Pass params: router.push({pathname: '/detail/[id]', params: {id: '123'}})

Best Practices

• Always use Pressable over TouchableOpacity or TouchableHighlight
• Enforce 44pt minimum touch targets — use hitSlop when visual is smaller
• Wrap every visible string in <Text> — no bare strings in JSX
• Use expo-image for all images (never RN Image)
• Add accessibilityLabel to every interactive element
• Use FlashList with estimatedItemSize for any list with >10 items
• Use contentContainerClassName for ScrollView/FlashList inner styling
• Add haptic feedback sparingly — primary actions only
• Test touch targets on real device (simulator touch is imprecise)

Anti-Patterns

• Using TouchableOpacity (deprecated — use Pressable)
• Touch targets smaller than 44pt without hitSlop compensation
• Bare strings without <Text> wrapper (runtime crash)
• Using RN Image instead of expo-image (no caching, no blurhash)
• Forgetting estimatedItemSize on FlashList
• Using FlatList for large datasets (FlashList is faster)
• Missing accessibilityLabel on interactive elements
• Using Alert.alert() for complex choices (use bottom sheet instead)
• Padding on className of ScrollView (use contentContainerClassName)
• Inline anonymous functions in FlashList renderItem (causes re-renders — extract component)