build.sh

cd /workspace/$1
VERSION_NAME=$(git describe)
VERSION_CODE=$(git rev-list --count master)
flutter build apk --build-name=$VERSION_NAME --build-number=$VERSION_CODE

cloudbuild.yaml

# Flutter CD configuration file with Cloud build

steps:

# clone the latest source codes 
- name: 'gcr.io/cloud-builders/git'
  args: ['clone', 'https://${_GIT_USERNAME}:${_GIT_PASSWORD}@bitbucket.org/${_ORG_NAME}/${_REPO_NAME}.git']
  dir: '/workspace'

# using flutter builder Docker image we have built previously to compile the repo
- name: 'gcr.io/$PROJECT_ID/flutter'
  entrypoint: '/bin/bash'
  args: ['build.sh', '${_REPO_NAME}']

# upload apk to google play store with Fastlane
- name: 'gcr.io/$PROJECT_ID/fastlane'
  args: ['supply', '--package_name','${_ANDROID_PACKAGE_NAME}', '--track', '${_ANDROID_RELEASE_CHANNEL}', '--json_key_data', '${_GOOGLE_PLAY_UPLOAD_KEY_JSON}', '--apk', '/workspace/${_REPO_NAME}/build/app/outputs/apk/release/app-release.apk']
timeout: 1200s