React Native Development

Build native iOS and Android apps with React Native and Expo.

Framework Options

Framework	Use When
Expo (Recommended)	Most apps, faster development, managed workflow
React Native CLI	Need custom native modules, brownfield apps
Expo with Dev Client	Best of both - Expo DX with native modules

---

Project Setup

Expo (Recommended)

npx create-expo-app@latest my-app
cd my-app
npx expo start

React Native CLI

npx @react-native-community/cli init MyApp
cd MyApp
npx react-native run-ios  # or run-android

---

Core Components

Basic Structure

import { View, Text, StyleSheet, ScrollView, SafeAreaView } from "react-native";

export default function App() {
  return (
    <SafeAreaView style={styles.container}>
      <ScrollView contentContainerStyle={styles.content}>
        <Text style={styles.title}>Hello World</Text>
      </ScrollView>
    </SafeAreaView>
  );
}

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: "#fff",
  },
  content: {
    padding: 16,
  },
  title: {
    fontSize: 24,
    fontWeight: "bold",
  },
});

Common Components

import {
  View,
  Text,
  Image,
  TextInput,
  TouchableOpacity,
  Pressable,
  FlatList,
  ActivityIndicator,
  Modal,
  Switch,
} from 'react-native';

// Touchable with feedback
<Pressable
  onPress={handlePress}
  style={({ pressed }) => [
    styles.button,
    pressed && styles.buttonPressed,
  ]}
>
  <Text>Press Me</Text>
</Pressable>

// Text Input
<TextInput
  value={text}
  onChangeText={setText}
  placeholder="Enter text"
  style={styles.input}
  autoCapitalize="none"
  keyboardType="email-address"
  returnKeyType="done"
  onSubmitEditing={handleSubmit}
/>

// Image
<Image
  source={{ uri: 'https://example.com/image.jpg' }}
  style={{ width: 100, height: 100 }}
  resizeMode="cover"
/>

---

Navigation

React Navigation Setup

npm install @react-navigation/native @react-navigation/native-stack
npx expo install react-native-screens react-native-safe-area-context

Stack Navigation

import { NavigationContainer } from "@react-navigation/native";
import { createNativeStackNavigator } from "@react-navigation/native-stack";

type RootStackParamList = {
  Home: undefined;
  Details: { itemId: string };
};

const Stack = createNativeStackNavigator<RootStackParamList>();

export default function App() {
  return (
    <NavigationContainer>
      <Stack.Navigator initialRouteName="Home">
        <Stack.Screen
          name="Home"
          component={HomeScreen}
          options={{ title: "My App" }}
        />
        <Stack.Screen
          name="Details"
          component={DetailsScreen}
          options={({ route }) => ({ title: route.params.itemId })}
        />
      </Stack.Navigator>
    </NavigationContainer>
  );
}

// Navigate
navigation.navigate("Details", { itemId: "123" });

// Go back
navigation.goBack();

Tab Navigation

import { createBottomTabNavigator } from "@react-navigation/bottom-tabs";
import { Ionicons } from "@expo/vector-icons";

const Tab = createBottomTabNavigator();

function TabNavigator() {
  return (
    <Tab.Navigator
      screenOptions={({ route }) => ({
        tabBarIcon: ({ focused, color, size }) => {
          const iconName =
            route.name === "Home"
              ? focused
                ? "home"
                : "home-outline"
              : focused
                ? "settings"
                : "settings-outline";
          return <Ionicons name={iconName} size={size} color={color} />;
        },
      })}
    >
      <Tab.Screen name="Home" component={HomeScreen} />
      <Tab.Screen name="Settings" component={SettingsScreen} />
    </Tab.Navigator>
  );
}

---

State Management

Zustand (Recommended)

import { create } from "zustand";
import { persist, createJSONStorage } from "zustand/middleware";
import AsyncStorage from "@react-native-async-storage/async-storage";

interface AuthStore {
  user: User | null;
  token: string | null;
  login: (user: User, token: string) => void;
  logout: () => void;
}

export const useAuthStore = create<AuthStore>()(
  persist(
    (set) => ({
      user: null,
      token: null,
      login: (user, token) => set({ user, token }),
      logout: () => set({ user: null, token: null }),
    }),
    {
      name: "auth-storage",
      storage: createJSONStorage(() => AsyncStorage),
    },
  ),
);

React Query

import {
  QueryClient,
  QueryClientProvider,
  useQuery,
} from "@tanstack/react-query";

const queryClient = new QueryClient();

// Wrap app
<QueryClientProvider client={queryClient}>
  <App />
</QueryClientProvider>;

// Use in component
function ItemList() {
  const { data, isLoading, error, refetch } = useQuery({
    queryKey: ["items"],
    queryFn: fetchItems,
  });

  if (isLoading) return <ActivityIndicator />;
  if (error) return <Text>Error: {error.message}</Text>;

  return (
    <FlatList
      data={data}
      renderItem={({ item }) => <ItemRow item={item} />}
      keyExtractor={(item) => item.id}
      onRefresh={refetch}
      refreshing={isLoading}
    />
  );
}

---

Styling

StyleSheet

const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: "#ffffff",
  },
  row: {
    flexDirection: "row",
    alignItems: "center",
    justifyContent: "space-between",
    padding: 16,
    borderBottomWidth: StyleSheet.hairlineWidth,
    borderBottomColor: "#ccc",
  },
  text: {
    fontSize: 16,
    color: "#333",
  },
  shadow: {
    shadowColor: "#000",
    shadowOffset: { width: 0, height: 2 },
    shadowOpacity: 0.1,
    shadowRadius: 4,
    elevation: 3, // Android
  },
});

NativeWind (Tailwind for RN)

npm install nativewind tailwindcss

import { Text, View } from "react-native";

export function Card() {
  return (
    <View className="bg-white rounded-lg p-4 shadow-md">
      <Text className="text-lg font-bold text-gray-900">Card Title</Text>
      <Text className="text-gray-600 mt-2">Card content goes here</Text>
    </View>
  );
}

---

Native Features

Camera (Expo)

import { Camera, CameraType } from "expo-camera";

function CameraScreen() {
  const [permission, requestPermission] = Camera.useCameraPermissions();
  const cameraRef = useRef<Camera>(null);

  const takePicture = async () => {
    if (cameraRef.current) {
      const photo = await cameraRef.current.takePictureAsync();
      console.log(photo.uri);
    }
  };

  if (!permission?.granted) {
    return <Button title="Grant Permission" onPress={requestPermission} />;
  }

  return (
    <Camera ref={cameraRef} style={styles.camera} type={CameraType.back}>
      <TouchableOpacity onPress={takePicture}>
        <Text>Take Photo</Text>
      </TouchableOpacity>
    </Camera>
  );
}

Push Notifications (Expo)

import * as Notifications from "expo-notifications";
import { useEffect } from "react";

Notifications.setNotificationHandler({
  handleNotification: async () => ({
    shouldShowAlert: true,
    shouldPlaySound: true,
    shouldSetBadge: false,
  }),
});

async function registerForPushNotifications() {
  const { status } = await Notifications.requestPermissionsAsync();
  if (status !== "granted") return;

  const token = await Notifications.getExpoPushTokenAsync();
  return token.data;
}

// Listen for notifications
useEffect(() => {
  const subscription = Notifications.addNotificationReceivedListener(
    (notification) => {
      console.log(notification);
    },
  );
  return () => subscription.remove();
}, []);

Location

import * as Location from "expo-location";

async function getLocation() {
  const { status } = await Location.requestForegroundPermissionsAsync();
  if (status !== "granted") return;

  const location = await Location.getCurrentPositionAsync({});
  return {
    latitude: location.coords.latitude,
    longitude: location.coords.longitude,
  };
}

---

Performance

FlatList Optimization

<FlatList
  data={items}
  renderItem={renderItem}
  keyExtractor={(item) => item.id}
  // Performance optimizations
  initialNumToRender={10}
  maxToRenderPerBatch={10}
  windowSize={5}
  removeClippedSubviews={true}
  getItemLayout={(data, index) => ({
    length: ITEM_HEIGHT,
    offset: ITEM_HEIGHT * index,
    index,
  })}
/>;

// Memoize render item
const renderItem = useCallback(
  ({ item }: { item: Item }) => <MemoizedItem item={item} />,
  [],
);

const MemoizedItem = memo(({ item }: { item: Item }) => (
  <View>
    <Text>{item.name}</Text>
  </View>
));

Image Optimization

import { Image } from "expo-image";

<Image
  source={{ uri: imageUrl }}
  style={{ width: 200, height: 200 }}
  contentFit="cover"
  placeholder={blurhash}
  transition={200}
  cachePolicy="memory-disk"
/>;

---

Testing

Jest + React Native Testing Library

import { render, fireEvent, waitFor } from "@testing-library/react-native";
import { LoginScreen } from "./LoginScreen";

describe("LoginScreen", () => {
  it("should login successfully", async () => {
    const onLogin = jest.fn();
    const { getByPlaceholderText, getByText } = render(
      <LoginScreen onLogin={onLogin} />,
    );

    fireEvent.changeText(getByPlaceholderText("Email"), "test@example.com");
    fireEvent.changeText(getByPlaceholderText("Password"), "password123");
    fireEvent.press(getByText("Login"));

    await waitFor(() => {
      expect(onLogin).toHaveBeenCalledWith({
        email: "test@example.com",
        password: "password123",
      });
    });
  });
});

---

App Store Deployment

Expo EAS Build

# Install EAS CLI
npm install -g eas-cli

# Configure
eas build:configure

# Build for iOS
eas build --platform ios

# Build for Android
eas build --platform android

# Submit to stores
eas submit --platform ios
eas submit --platform android

app.json Configuration

{
  "expo": {
    "name": "My App",
    "slug": "my-app",
    "version": "1.0.0",
    "ios": {
      "bundleIdentifier": "com.mycompany.myapp",
      "buildNumber": "1"
    },
    "android": {
      "package": "com.mycompany.myapp",
      "versionCode": 1
    }
  }
}

---

Best Practices

DO:

• Use Expo for faster development
• Implement proper TypeScript types
• Use FlashList for large lists
• Handle keyboard properly
• Test on real devices

DON'T:

• Inline styles in render
• Skip memoization for lists
• Ignore platform differences
• Block JS thread with heavy computation
• Forget to handle deep linking

---

New Architecture (React Native 0.76+)

React Native's New Architecture replaces the legacy bridge with a more performant, synchronous layer.

Core Components

Component	Replaces	Benefit
Fabric	Paper	Synchronous rendering, concurrent features
TurboModules	Native Modules	Lazy loading, synchronous access, type safety
JSI	Bridge	Direct JS-to-native communication, no JSON
Bridgeless Mode	Bridge	Removes bridge entirely, lower memory usage

Enabling New Architecture

// app.json (Expo)
{
  "expo": {
    "newArchEnabled": true
  }
}

# ios/Podfile (bare React Native)
ENV['RCT_NEW_ARCH_ENABLED'] = '1'

TurboModules (Type-Safe Native Modules)

// NativeCalculator.ts
import type { TurboModule } from "react-native";
import { TurboModuleRegistry } from "react-native";

export interface Spec extends TurboModule {
  add(a: number, b: number): number; // Synchronous!
  fetchData(url: string): Promise<string>; // Async
}

export default TurboModuleRegistry.getEnforcing<Spec>("NativeCalculator");

Fabric Components (New Renderer)

Fabric enables concurrent rendering features from React 18/19, including Suspense for data fetching, transitions, and automatic batching.

---

Expo Router (File-Based Routing)

npx create-expo-app@latest --template tabs

File Structure

app/
├── _layout.tsx          # Root layout
├── index.tsx            # Home screen (/)
├── (tabs)/              # Tab group
│   ├── _layout.tsx      # Tab navigator
│   ├── index.tsx        # First tab
│   └── settings.tsx     # Settings tab
├── [id].tsx             # Dynamic route (/123)
├── modal.tsx            # Modal screen
└── +not-found.tsx       # 404 screen

Layout and Navigation

// app/_layout.tsx
import { Stack } from "expo-router";

export default function RootLayout() {
  return (
    <Stack>
      <Stack.Screen name="(tabs)" options={{ headerShown: false }} />
      <Stack.Screen name="modal" options={{ presentation: "modal" }} />
    </Stack>
  );
}

// Navigate with type-safe links
import { Link, router } from "expo-router";

<Link href="/settings">Settings</Link>
<Link href={{ pathname: "/[id]", params: { id: "123" } }}>Details</Link>

// Programmatic navigation
router.push("/settings");
router.replace("/login");
router.back();

---

React 19 Compatibility

React Native supports React 19 features when using New Architecture:

• use() hook for reading promises and context
• ref as prop (no forwardRef needed)
• React Compiler support for auto-memoization
• useActionState and useOptimistic for form handling

---

EAS Update (OTA Updates)

# Install EAS CLI
npm install -g eas-cli

# Configure updates
eas update:configure

# Push an OTA update (no app store review)
eas update --branch production --message "Bug fix for login"
eas update --branch preview --message "New feature preview"

// Check for updates in app
import * as Updates from "expo-updates";

async function checkForUpdates() {
  const update = await Updates.checkForUpdateAsync();
  if (update.isAvailable) {
    await Updates.fetchUpdateAsync();
    await Updates.reloadAsync(); // Apply update
  }
}

---

Hermes Engine

Hermes is the default JS engine for React Native, optimized for mobile:

• Faster startup via bytecode precompilation
• Lower memory usage than JavaScriptCore
• Better debugging with Chrome DevTools Protocol

// app.json - Hermes is enabled by default in Expo SDK 52+
{
  "expo": {
    "jsEngine": "hermes"
  }
}

---

Expo SDK 52+ Features

Feature	Description
Expo Router v4	File-based routing with API routes
expo-camera (next)	Camera API with barcode scanning
expo-video	Modern video player replacing expo-av
expo-sqlite	SQLite with synchronous API via JSI
DOM Components	Render web components inside React Native
React 19 support	Full React 19 features with New Architecture
Universal links	Deep linking configured via app.json