Building React Native apps for Android

App Center can build React Native apps using React Native version 0.34 or newer.

To start building your first React Native Android app, you must:

1. Connect to your repository service account (GitHub, Bitbucket, VSTS, Azure DevOps).
2. Select a repository and a branch where your app lives.
3. Choose the project's package.json that you want to build.
4. Set up your first build.

1. Linking your repository

If you haven't previously connected to your repository service account, you must do this first. Once your account is connected, select the repository where your React Native project is located. You must have admin and pull permissions to set up a build for a repository.

2. Selecting a branch

After selecting a repository, select the branch you want to build. By default, App Center lists all active branches.

3. Setting up your first build

Before your first build, you must configure the React Native project.

3.1. Project

Select your project’s package.json. App Center will automatically extract information from its associated build.gradle (app level) file, including dependencies, build tools version, build types, and product flavors.

3.2. Build variant

The available build variants will populate from the Build Types and Product Flavors specified in the project's build.gradle (app level) file. Select which build variant should be built.

3.3. Node.js version

Select the Node.js version to use for the build Read more about how to select Node.js version

3.4. Build triggers

By default, a new build is triggered every time a developer pushes to a configured branch. This is referred to as "Continuous Integration". If you prefer to trigger a new build manually, you can change this setting in the configuration pane.

3.5. Build Android App Bundle (.aab)

The Android App Bundle is a distribution format that can be uploaded to the Play Store. It's used to generate optimized APKs for specific devices. You can find out more about the Android App Bundle in the official Android documentation, which also helps you understand whether you want to build a bundle along with your regular .apk.

Toggle on the option for Android App Bundle to produce an .aab in addition to the .apk. If the build.gradle (app level) file contains the android.bundle block, this option will automatically be toggled on.

3.6. Increment version number

When enabled, the version code in the AndroidManifest.xml of your app automatically increments for each build. The change happens during the actual build and won't be committed to your repository.

3.7. Launch your successful build on a real device

Use the newly produced APK file to test if your app starts on a real device. Launch tests will add approximately 10 more minutes to the total build time. Read more about how to configure launch tests.

3.8. Code signing

A successful build will produce an .apk file and an additional .aab file if enabled. To release the build to the Play Store, it must be signed with a valid certificate stored in a keystore. To sign the builds produced from a branch, enable code signing in the configuration pane, upload your keystore to your repository, and provide the relevant values in the configuration pane. You can read more about Android code signing App Center's Android code signing documentation. The .aab will be signed using the same credentials as the .apk.

3.9. Distribute the build

You can configure each successful build from a branch to be distributed to a previously created distribution group or a store destination. You can add a new distribution group or configure a store connection from within the Distribute service. There's always a default distribution group called "Collaborators" that includes all the users who have access to the app.

4. Build results

After a build triggers, the build will be in one of the following states:

• queued - the build is in a queue waiting for resources to be freed up
• building - the build is running the predefined tasks
• succeeded - the build is completed and it's succeeded
• failed - the build has completed but it's failed; you can troubleshoot what went wrong by downloading and inspecting the build log
• canceled - the build has been canceled by a user action or it's timed out

4.1. Build logs

For a completed build (succeeded or failed), download the logs to understand more about how the build went. App Center provides an archive with the following files:

|-- 1_build.txt (this is the general build log)
|-- build (this folder contains a separate log file for each build step)
    |-- <build-step-1>
    |-- <build-step-2>
    |--
    |-- <build-step-n> (e.g. n_Post Job Cleanup.txt)

The build step-specific logs (located in the build/ directory of the archive) are helpful for troubleshooting and understanding in what step and why the build failed.

4.2. The app (.apk)

The .apk file is an Android application packaged file that stores the Android app. If the build has been correctly signed, the app can be installed on a real device and deployed to the Play Store. If the build hasn't been signed, the app can run on an emulator or be used for other purposes.

5. Supported versions and requirements

The minimum version supported to build Android apps is 5.0 (API level 21). Android apps can have a lower minimum API level required to run, but must target at least API level 21.

6. Build tips

6.1. Yarn

The Yarn package manager is a faster, more deterministic replacement for npm. If a yarn.lock file is present in your repository next to package.json, then App Center will use Yarn, doing yarn install at the start of the build. Otherwise, it will do npm install.

6.2. Custom build scripts

There are several options for running scripts before App Center's default build commands are executed.

• Create a postinstall script in your project's package.json file. This script will automatically execute after your dependencies are installed.

    "scripts": {
      ...
      "postinstall" : "npx jetify" // other examples: "node ./postinstall.js" or "./postinstall.sh"
    },
  

• Write a shell script using App Center's custom build scripts functionality.

  #!/usr/bin/env bash
  
  # Example: Authenticate with private NPM registry
  echo "//registry.npmjs.org/:_authToken=$NPM_AUTH_TOKEN" > ~/.npmrc
  
  # Example: Add your signing key file (from base64 encoded environment variable)
  base64 -d <<< "$ANDROID_JSON_KEY_FILE" > android/keystores/json_key_file.json
  

6.3. Building multiple APKs

For React Native on Android, universal APK generation is disabled by default. If your app configuration is set up to build multiple APKs, for example different ones per CPU architecture or screen configuration, you need to make sure a universal APK is built as well. App Center's build system works with one main APK file and will ignore all APKs specific to a certain CPU/ABI or screen density.

To learn more about APK splits and how to build a universal APK, read the corresponding Android developer guide. Consequently, make sure that universalApk is set to true for your React Native build configuration.