mobile-design

Wrap list items in React.memo, memoize renderItem with useCallback, use a stable keyExtractor with item IDs instead of indexes, and provide getItemLayout for fixed-height items. Never use ScrollView with map for long lists since it renders all items at once.

Choose React Native with Expo when you need OTA updates and have a web team; choose Flutter for pixel-perfect identical UI across platforms; choose native SwiftUI or Kotlin for maximum performance and deep OS integration. The decision depends on team skills and project constraints.

iOS requires 44pt minimum touch targets and Android requires 48dp, with at least 8-12px spacing between adjacent targets. Primary actions should sit in the thumb zone at the bottom of the screen for one-handed use.

Store tokens in iOS Keychain, Android EncryptedSharedPreferences, or Expo SecureStore—never in AsyncStorage, which is plain text and accessible on rooted devices. Use short-lived access tokens in memory with long-lived refresh tokens in secure storage.

Excessive rebuilds usually come from setState overuse and missing const constructors. Add const to every widget that does not depend on state, and use ValueListenableBuilder or provider selectors to rebuild only the widgets that actually changed.

Dark mode saves significant battery only on OLED screens, where black pixels are fully off. Use true black (#000000) for backgrounds to maximize savings, and desaturate colors in dark mode rather than simply inverting the light palette.