Fastlane - Google Play

Build Flutter apps and automatically upload to Google Play with Fastlane (free)

When a Flutter app starts having many releases, manually building AAB and uploading to Google Play Console is very easy to get wrong. I use Fastlane to automate the full Android release flow.

My goals are:

• Reduce manual steps when shipping a new version.

• Standardize the process for the whole team.

• Clearly separate lanes: internal, alpha, production.

Prepare the Fastlane environment

Step 1: Install Bundler

gem install bundler

Step 2: Create Gemfile

Create a Gemfile at project root:

source "https://rubygems.org"
gem "fastlane"

Step 3: Install local dependencies

bundle config set --local path 'vendor/bundle'
bundle install

I prefer this way to lock Fastlane version per project.

Create a service account for Google Play API

Step 1: Create a service account in Google Cloud

Go to: Google Cloud Service Accounts

Do the following:

• Select or create a new project.

• Create a service account named fastlane-deploy.

• Assign role Editor (for production, consider least-privilege roles).

• Go to Keys -> Add key -> select JSON to download the key.

• Copy the service account email (format [e-mail]).

Step 2: Grant permissions in Google Play Console

Go to: Google Play Console

Open Google Play Console -> Users and permissions -> Invite new user:

• Paste the service account email.

• Grant the proper release permissions.

• No email confirmation is required.

Put the JSON key into the project

Put the JSON file in project, for example:

android/fastlane/play-service-account.json

If you want better security, add this to .gitignore:

android/fastlane/*.json

Initialize Fastlane for Android

Go to android folder and run:

cd android
fastlane init

When prompted, fill in:

• Package name: com.example.app

• JSON path: for example ./android/fastlane/play-service-account.json

• Download existing metadata and setup metadata management? -> y

After this step, Fastlane will create Fastfile and Appfile.

Configure Fastfile

Edit android/fastlane/Fastfile like this:

default_platform(:android)

platform :android do

  ########################################
  # INTERNAL TRACK (not public)
  ########################################
  desc "Upload to internal testing"
  lane :internal do
    # Build AAB
    gradle(
      task: "bundle",
      build_type: "Release"
    )

    # Upload to Google Play
    upload_to_play_store(
      track: "internal",
      json_key: "fastlane/play-service-account.json",
      package_name: "com.example.app",
      aab: "app/build/outputs/bundle/release/app-release.aab"
    )
  end

  ########################################
  # CLOSED TEST (alpha)
  ########################################
  desc "Upload to closed testing"
  lane :alpha do
    upload_to_play_store(
      track: "alpha",
      json_key: "fastlane/play-service-account.json",
      package_name: "com.example.app",
      aab: "app/build/outputs/bundle/release/app-release.aab"
    )
  end

  ########################################
  # PRODUCTION (public store)
  ########################################
  desc "Upload to production"
  lane :production do
    upload_to_play_store(
      track: "production",
      release_status: "completed",     # Auto publish
      json_key: "fastlane/play-service-account.json",
      package_name: "com.example.app",
      aab: "app/build/outputs/bundle/release/app-release.aab"
    )
  end

end

Run release lanes in android folder

fastlane internal
fastlane alpha
fastlane production

Quick explanation:

• internal: upload to internal track (not public).

• alpha: upload to closed testing.

• production: upload to public store.

Fix common issue: Fastlane cannot build AAB because Java is not aligned

Sync JDK for Flutter and Fastlane

Issue I faced:

• flutter build appbundle works.

• But fastlane build fails because Java versions are different.

Fix (example using Java 17 on macOS Apple Silicon):

brew install openjdk@17
sudo ln -sfn /opt/homebrew/opt/openjdk@17/libexec/openjdk.jdk /Library/Java/JavaVirtualMachines/openjdk-17.jdk

Add to ~/.zshrc:

export JAVA_HOME="/opt/homebrew/opt/openjdk@17"
export PATH="$JAVA_HOME/bin:$PATH"

Reload shell and check:

source ~/.zshrc
java -version

Expected result: openjdk version "17.x.x".

Run Fastlane again:

cd android
fastlane internal

If running from project root, you can use:

fastlane android internal

Additional notes

• For iOS, I use devices.txt to manage test devices and auto-add devices in Fastlane flow.

• This article focuses on Android/Google Play, I will publish a separate iOS article next time.

Conclusion

Fastlane helps me turn a release process with many manual steps into a few fixed commands. After setup, for each new release I only need to bump version and run the corresponding lane.

It becomes much faster if you combine it with Make. If you do not know it yet, check this article.

Make

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