This project was bootstrapped with Create React Native App.
Below you'll find information about performing common tasks. The most recent version of this guide is available here.
If Yarn was installed when the project was initialized, then dependencies will have been installed via Yarn, and you should probably use it to run these commands as well. Unlike dependency installation, command running syntax is identical for Yarn and NPM at the time of this writing.
Runs your app in development mode.
Open it in the Expo app on your phone to view it. It will reload if you save edits to your files, and you will see build errors and logs in the terminal.
Sometimes you may need to reset or clear the React Native packager's cache. To do so, you can pass the --reset-cache flag to the start script:
npm start --reset-cache
# or
yarn start --reset-cache
Runs the jest test runner on your tests.
Like npm start, but also attempts to open your app in the iOS Simulator if you're on a Mac and have it installed.
Like npm start, but also attempts to open your app on a connected Android device or emulator. Requires an installation of Android build tools (see React Native docs for detailed setup). We also recommend installing Genymotion as your Android emulator. Once you've finished setting up the native build environment, there are two options for making the right copy of adb available to Create React Native App:
- Make sure that you can run adb from your terminal.
- Open Genymotion and navigate to
Settings -> ADB. Select “Use custom Android SDK tools” and update with your Android SDK directory.
- Find Genymotion’s copy of adb. On macOS for example, this is normally
/Applications/Genymotion.app/Contents/MacOS/tools/. - Add the Genymotion tools directory to your path (instructions for Mac, Linux, and Windows).
- Make sure that you can run adb from your terminal.
This will start the process of "ejecting" from Create React Native App's build scripts. You'll be asked a couple of questions about how you'd like to build your project.
Warning: Running eject is a permanent action (aside from whatever version control system you use). An ejected app will require you to have an Xcode and/or Android Studio environment set up.
You can configure some of Create React Native App's behavior using environment variables.
When starting your project, you'll see something like this for your project URL:
exp://192.168.0.2:19000
The "manifest" at that URL tells the Expo app how to retrieve and load your app's JavaScript bundle, so even if you load it in the app via a URL like exp://localhost:19000, the Expo client app will still try to retrieve your app at the IP address that the start script provides.
In some cases, this is less than ideal. This might be the case if you need to run your project inside of a virtual machine and you have to access the packager via a different IP address than the one which prints by default. In order to override the IP address or hostname that is detected by Create React Native App, you can specify your own hostname via the REACT_NATIVE_PACKAGER_HOSTNAME environment variable:
Mac and Linux:
REACT_NATIVE_PACKAGER_HOSTNAME='my-custom-ip-address-or-hostname' npm start
Windows:
set REACT_NATIVE_PACKAGER_HOSTNAME='my-custom-ip-address-or-hostname'
npm start
The above example would cause the development server to listen on exp://my-custom-ip-address-or-hostname:19000.
Create React Native App does a lot of work to make app setup and development simple and straightforward, but it's very difficult to do the same for deploying to Apple's App Store or Google's Play Store without relying on a hosted service.
Expo provides free hosting for the JS-only apps created by CRNA, allowing you to share your app through the Expo client app. This requires registration for an Expo account.
Install the exp command-line tool, and run the publish command:
$ npm i -g exp
$ exp publish
You can also use a service like Expo's standalone builds if you want to get an IPA/APK for distribution without having to build the native code yourself.
If you want to build and deploy your app yourself, you'll need to eject from CRNA and use Xcode and Android Studio.
This is usually as simple as running npm run eject in your project, which will walk you through the process. Make sure to install react-native-cli and follow the native code getting started guide for React Native.
