expo-dev-launcher

expo-dev-launcher is an npm package installable in any Expo or React Native project. Once installed, any Debug builds of your application will gain the ability to load projects from Expo CLI. Release builds of your application will not change other than the addition of a few header files. This package is intended to be included in your project through expo-dev-client.

Documentation

You can find more information in the Expo documentation.

Contributing

The expo-dev-launcher repository consists of two different parts, the exported package, which includes the native functions, located in the android, ios and src folders and the Dev Launcher interface, located under the bundle folder.

Local development is usually done through bare-expo.

To use dev-client when running bare-expo on Android, open MainApplication.java and set the USE_DEV_CLIENT value to true.

- static final boolean USE_DEV_CLIENT = false;
+ static final boolean USE_DEV_CLIENT = true;

To use dev-client when running bare-expo on iOS, open AppDelegate.mm and set the USE_DEV_CLIENT value to YES.

- BOOL useDevClient = NO;
+ BOOL useDevClient = YES;

Making JavaScript changes inside the bundle folder

To update the JavaScript code inside the bundle folder, you need to run the dev-launcher bundler locally.

1. Navigate to the dev-launcher package: cd packages/expo-dev-launcher
2. Start the Metro bundler: yarn start
3. Adjust the dev-launcher URL to point to your local bundler

On Android

Open DevLauncherController.kt and update the DEV_LAUNCHER_HOST value to your bundler URL.

E.g.

- private val DEV_LAUNCHER_HOST: String? = null
+ private val DEV_LAUNCHER_HOST: String? = "10.0.2.2:8090";

On iOS

3.1. Open another terminal window and navigate to the ios folder inside bare-expo

3.2. Export the EX_DEV_LAUNCHER_URL variable in your shell before running pod install.

E.g.

export EX_DEV_LAUNCHER_URL=http://localhost:8090

This will cause the controller to see if the expo-launcher packager is running, and if so, use that instead of the prebuilt bundle.

3.3. Run pod install

4. Recompile bare-expo
5. Play with your changes on a simulator or device
6. Once you've made all the necessary changes run yarn bundle to update the embedded bundle