Signing, Versioning & Build Variants

Copy code// app/build.gradle.kts
android {
    signingConfigs {
        create("release") {
            // Read from environment variables — injected by CI
            storeFile = file(System.getenv("KEYSTORE_PATH") ?: "debug.keystore")
            storePassword = System.getenv("KEYSTORE_PASSWORD") ?: ""
            keyAlias = System.getenv("KEY_ALIAS") ?: ""
            keyPassword = System.getenv("KEY_PASSWORD") ?: ""
        }
    }

    buildTypes {
        release {
            signingConfig = signingConfigs.getByName("release")
            isMinifyEnabled = true
            proguardFiles(getDefaultProguardFile("proguard-android-optimize.txt"), "proguard-rules.pro")
        }
    }
}

Copy code# GitHub Actions: decode base64-encoded keystore from secret
- name: Decode keystore
  run: |
    echo "${{ secrets.KEYSTORE_BASE64 }}" | base64 -d > app/release.keystore

- name: Build release APK
  env:
    KEYSTORE_PATH: release.keystore
    KEYSTORE_PASSWORD: ${{ secrets.KEYSTORE_PASSWORD }}
    KEY_ALIAS: ${{ secrets.KEY_ALIAS }}
    KEY_PASSWORD: ${{ secrets.KEY_PASSWORD }}
  run: ./gradlew bundleRelease

Copy code// app/build.gradle.kts
android {
    defaultConfig {
        // versionCode: monotonically increasing integer
        // Use timestamp for CI builds: YYYYMMDDNN (e.g., 2024030401)
        versionCode = System.getenv("VERSION_CODE")?.toInt() ?: 1

        // versionName: semantic version from git tag
        versionName = System.getenv("VERSION_NAME") ?: "1.0.0-dev"
    }
}

Copy code# Derive version from git tag (e.g., v2.3.1)
- name: Set version
  run: |
    TAG=${GITHUB_REF#refs/tags/v}
    echo "VERSION_NAME=$TAG" >> $GITHUB_ENV
    # versionCode: date-based YYYYMMDDNN
    echo "VERSION_CODE=$(date +%Y%m%d)01" >> $GITHUB_ENV

Copy codeandroid {
    flavorDimensions("environment")

    productFlavors {
        create("dev") {
            dimension = "environment"
            applicationIdSuffix = ".dev"
            versionNameSuffix = "-dev"
            buildConfigField("String", "API_BASE_URL", "\"https://dev-api.example.com\"")
            buildConfigField("Boolean", "ENABLE_LOGGING", "true")
        }

        create("staging") {
            dimension = "environment"
            applicationIdSuffix = ".staging"
            versionNameSuffix = "-staging"
            buildConfigField("String", "API_BASE_URL", "\"https://staging-api.example.com\"")
            buildConfigField("Boolean", "ENABLE_LOGGING", "true")
        }

        create("production") {
            dimension = "environment"
            buildConfigField("String", "API_BASE_URL", "\"https://api.example.com\"")
            buildConfigField("Boolean", "ENABLE_LOGGING", "false")
        }
    }

    buildTypes {
        debug {
            isDebuggable = true
            isMinifyEnabled = false
        }
        release {
            isDebuggable = false
            isMinifyEnabled = true
        }
    }
}

Copy code// Usage in code
class NetworkConfig {
    val baseUrl: String = BuildConfig.API_BASE_URL
    val loggingEnabled: Boolean = BuildConfig.ENABLE_LOGGING
}

Copy codeapp/src/
├── main/           shared across all variants
├── dev/            dev-specific resources/code
├── staging/        staging-specific
└── production/     prod-specific (e.g., Firebase google-services.json)

Copy code// src/dev/kotlin/com/myapp/FlipperInitializer.kt
object FlipperInitializer {
    fun init(context: Context) { Flipper.start(context) }
}

// src/production/kotlin/com/myapp/FlipperInitializer.kt
object FlipperInitializer {
    fun init(context: Context) { }  // No-op in production
}