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Image Code Scanner Example (Expo)

This app demonstrates how to use react-native-image-code-scanner in an Expo project.

What this example includes

  • Pick image from camera or gallery (expo-image-picker)
  • Select barcode formats before scanning
  • Scan with automatic preprocessing (built into the library)
  • Show scan results and execution time

Requirements

  • Node.js >=18
  • Yarn 3.6.1 via Corepack
  • iOS: Xcode (for native build)
  • Android: Android Studio + SDK (for native build)

Use Yarn for this workspace. Do not mix npm installs with the generated native projects.

Install

From the repository root:

yarn install

Metro / Fast Refresh

Run Metro from the example folder:

yarn expo start --clear --dev-client --host localhost
  • Press i for iOS simulator.
  • Press a for Android emulator.
  • If the app was opened before Metro started, terminate the app and open it again from Metro.
  • JS/TSX changes use Fast Refresh. Native, Podfile, Gradle, or architecture changes require rebuild.

New Architecture

app.json is the source of truth:

{
  "expo": {
    "newArchEnabled": true
  }
}

After changing this value, run prebuild --clean and rebuild the native app.

iOS Build

Clean regenerate iOS and build:

cd example
yarn expo prebuild --clean --platform ios
yarn expo run:ios --no-build-cache

With Metro running in another terminal:

cd example
yarn expo run:ios --no-bundler --no-build-cache

Verify New Architecture:

cat ios/Podfile.properties.json
# expect: "newArchEnabled": "true"

Android Build

Clean regenerate Android and build:

cd example
yarn expo prebuild --clean --platform android
yarn expo run:android --no-build-cache

With Metro running in another terminal:

cd example
yarn expo run:android --no-bundler --no-build-cache

Verify New Architecture:

grep newArchEnabled android/gradle.properties
# expect: newArchEnabled=true

Notes

  • Preprocessing options are configurable in the UI: contrast, grayscale, rotations.
  • At least one barcode format must stay selected.
  • Permissions for camera and media library are requested at runtime.
  • Expo Go is not enough for scanning because this package uses native modules.

Troubleshooting

  • White screen: Metro is probably not running or the app opened before Metro. Start Metro, terminate the app, then press i/a.
  • No Fast Refresh: confirm http://127.0.0.1:8081/status works and open the app from Metro.
  • iOS native issue after config changes: run yarn expo prebuild --clean --platform ios.
  • Android native issue after config changes: run yarn expo prebuild --clean --platform android.
  • Metro cache issue: run yarn expo start --clear --dev-client --host localhost.

Scripts

  • yarn start: Start Expo dev server
  • yarn ios: Build and run on iOS
  • yarn android: Build and run on Android
  • yarn prebuild: Generate native projects
  • yarn prebuild:clean: Regenerate native projects from scratch

Related docs