Expo is a set of tools, libraries, and services that let you build native iOS and Android apps by writing JavaScript. This repository is where the Expo client software is developed, and includes the client apps, modules, apps, and more.
Click here to view our documentation for developing on Expo. If you're new to the Expo community, click here to view the Expo Community Guidelines. Thank you for helping keep the Expo community open and welcoming!
Introduction
This is the source code for the Expo client app used to view experiences published to the Expo service. If you want to build and install the Expo client directly onto a device, you're in the right place. Note that if you just want to install the Expo client app on a simulator, you do not need to build it from source. Instead, you should follow the instructions here.
To build the Expo client app, follow the instructions in the Set Up section below. Use the expo-cli command line to use Expo's infrastructure to build your app.
Please ask us on the forums if you get stuck.
Disclaimers:
If you want to build a standalone app that has a custom icon and name, see our documentation here. You're in the wrong place, you shouldn't need to build the Expo clients from source.
If you need to make native code changes to your Expo project, such as adding custom native modules, we can generate a native project for you. You're in the wrong place, you shouldn't need to build the Expo clients from source.
Set Up
Note: We support building the clients only on macOS.
- Install nix (currently
curl https://nixos.org/nix/install | sh
) - Install direnv (to do this with nix, run
nix-env -iA nixpkgs.direnv
) - Clone this repo; we recommend cloning it to a directory whose full path does not include any spaces (you should clone all the submodules with
git clone --recurse-submodules
) - Run
yarn
in thetools-public
directory.
iOS
- Make sure you have latest non-beta Xcode installed.
- Run
git lfs pull
. - Run
./generate-files-ios.js
in thetools-public
directory. - Open and run
ios/Exponent.xcworkspace
in Xcode.
Android
- Make sure you have Android Studio 3 installed
- Run
android/install-ndk-17c.sh
to get the required version of the Android NDK. - See "Running on a Device"
Running on a Device
iOS
- In Xcode's menu bar, open the Xcode drop-down menu, and select Preferences. Then in the Accounts tab of the preferences menu, add add your personal or team apple developer account.
- Connect your test device to your computer with a USB cable.
- In Xcode's menu bar, open the Product drop-down menu, select Destination, then in the Device grouping select your device.
- In the project navigator, select the Exponent project to bring up the project's settings, and then:
- In the General tab, in the Identity section, put in a unique Bundle Identifier.
- Also in the General tab, in the Signing section, select your personal or team apple developer account as your Team, and create a new signing certificate by clicking Fix Issue.
- Finally, run the build
Android
- If the Play Store version of the Expo Client App is installed on your test device, uninstall it.
- Connect your test device to your computer with a USB cable.
- Run
fastlane android start
, or alternately open theandroid
directory in Android Studio, start it, and in the Select Deployment Target dialog, select your device.
Standalone Apps
If you don't need custom native code outside of the Expo SDK, head over to our documentation on building standalone apps without needing Android Studio and Xcode.
If you're still here, make sure to follow the Configure app.json section of the docs before continuing. You'll need to add the appropriate fields to your app.json
before the standalone app scripts can run. Once that's done, continue on to the platform-specific instructions.
Android
The Android standalone app script creates a new directory android-shell-app
with the modified Android project in it. It then compiles that new directory giving you a signed or unsigned .apk
depending on whether you provide a keystore and the necessary passwords. If there are issues with the app you can open the android-shell-app
project in Android Studio to debug.
Here are the steps to build a standalone Android app:
- Publish your experience with Expo CLI. Note the published URL.
cd tools-public
.- If you want a signed
.apk
, rungulp android-shell-app --url [the published experience url] --sdkVersion [sdk version of your experience] --keystore [path to keystore] --alias [keystore alias] --keystorePassword [keystore password] --keyPassword [key password] --workingDir=../
. - If you don't want a signed
.apk
, rungulp android-shell-app --url [the published experience url] --sdkVersion [sdk version of your experience] --workingDir=../
. - The
.apk
file will be at/tmp/shell-signed.apk
for a signed.apk
or at/tmp/shell-debug.apk
for an unsigned.apk
. adb install
the.apk
file to test it.- Upload to the Play Store!
iOS
The iOS standalone app script has two actions, build
and configure
. build
creates an archive or a simulator build of the Expo iOS workspace. configure
accepts a path to an existing archive and modifies all its configuration files so that it will run as a standalone Expo experience rather than as the Expo client app.
Here are the steps to build a standalone iOS app:
- Publish your experience with Expo CLI. Note the published URL.
cd tools-public
.gulp ios-shell-app --action build --type [simulator or archive] --configuration [Debug or Release]
- The resulting archive will be created at
../shellAppBase-[type]
. gulp ios-shell-app --url [the published experience url] --action configure --type [simulator or archive] --archivePath [path to ExpoKitApp.app] --sdkVersion [sdk version of your experience] --output your-app.tar.gz
- This bundle is not signed and cannot be submitted to iTunes Connect as-is; you'll need to manually sign it if you'd like to submit it to Apple. Fastlane is a good option for this. Also, Expo will do this for you if you don't need to build this project from source.
- If you created a simulator build in the first step, unpack the tar.gz using
tar -xvzf your-app.tar.gz
. Then you can run this on iPhone Simulator usingxcrun simctl install booted <app path>
andxcrun simctl launch booted <app identifier>
. Another alternative which some people prefer is to install the ios-sim tool and then useios-sim launch <app path>
. - There are a few more optional flags you can pass to this script. They are all documented in the block comments inside
xdl/src/detach/IosShellApp.js
.
Modifying JS Code
The Expo client apps run a root Expo project in addition to native code. By default this will use a published version of the project, so any changes made in the home
directory will not show up without some extra work.
Serve this project locally by running expo start
from the home
directory. On iOS, you'll additionally need to set DEV_KERNEL_SOURCE
to LOCAL
in EXBuildConstants.plist
(the default is PUBLISHED
).
The native Android Studio and XCode projects have a build hook which will find this if expo start
is running. Keep this running and rebuild the app on each platform.
Project Layout
android
contains the Android project.home
contains the JavaScript source code of the app.ios
contains the iOS project.ios/Exponent.xcworkspace
is the Xcode workspace. Always open this instead ofExponent.xcodeproj
because the workspace also loads the CocoaPods dependencies.tools-public
contains build and configuration tools.template-files
contains templates for files that require private keys. They are populated using the keys intemplate-files/keys.json
.template-files/ios/dependencies.json
specifies the CocoaPods dependencies of the app.
Tests
iOS
For native XCTest unit tests:
- Press Command+U in XCode to build and test the
Tests
unit test target. - Alternatively, run
fastlane ios test
from the parent directory ofios
.
For JS integration tests, test the ExponentIntegrationTests
target (not included in the default test scheme). This target requires you to configure EXTestEnvironment.plist
with a key testSuiteUrl
whose value is the URL to load some version of Expo's test-suite app. This will run a bunch of Jasmine tests against the Expo SDK.
Contributing
Please check with us before putting work into a Pull Request! It is often harder to maintain code than it is to write it. The best place to talk to us is on Slack at https://slack.expo.io.
License
The Expo source code is made available under the MIT license. Some of the dependencies are licensed differently, with the BSD license, for example.