Build System

1. Gradle Basics

Q: What is Gradle and how does it work in Android?

Gradle is the build automation tool for Android. It:

• Compiles source code
• Manages dependencies
• Creates APK/AAB packages
• Runs tests
• Signs and optimizes releases

Android uses the Android Gradle Plugin (AGP) which adds Android-specific tasks.

Q: What are the key Gradle files?

Q: Groovy DSL vs Kotlin DSL?

Kotlin DSL is now recommended for new projects.

2. Build Variants

Q: What are build types and product flavors?

Build types define how the app is built:

• debug: Debuggable, no optimization, debug signing
• release: Optimized, minified, production signing

Product flavors define different versions:

• free / paid
• demo / full
• staging / production

Variants = Build Type × Product Flavors (e.g., freeDebug, paidRelease)

Q: What are common build type configurations?

Q: How do you configure different API endpoints per flavor?

Use buildConfigField:

productFlavors {
    create("staging") {
        buildConfigField("String", "API_URL", "\"https://staging.api.com\"")
    }
    create("production") {
        buildConfigField("String", "API_URL", "\"https://api.com\"")
    }
}

Access via BuildConfig.API_URL in code.

3. Dependencies

Q: Explain dependency configurations.

Q: implementation vs api?

• implementation: Dependency is internal, doesn't leak to consumers
• api: Dependency is part of public API, consumers can use it

Prefer implementation—faster builds, better encapsulation.

Q: How do you handle dependency conflicts?

• Gradle uses highest version by default
• Use constraints to force specific version
• Use exclude to remove transitive dependencies
• Check conflicts with ./gradlew dependencies
• Use version catalogs for consistency

4. Version Catalogs

Q: What are version catalogs?

Centralized dependency management in libs.versions.toml:

[versions]
kotlin = "1.9.20"
compose = "1.5.4"

[libraries]
compose-ui = { group = "androidx.compose.ui", name = "ui", version.ref = "compose" }

[bundles]
compose = ["compose-ui", "compose-material", "compose-foundation"]

[plugins]
kotlin = { id = "org.jetbrains.kotlin.android", version.ref = "kotlin" }

Usage: implementation(libs.compose.ui)

Benefits: Single source of truth, type-safe, IDE support.

5. ProGuard/R8

Q: What is R8 and what does it do?

R8 is Android's code shrinker (replaced ProGuard). It:

• Shrinks: Removes unused code
• Optimizes: Inlines methods, removes dead branches
• Obfuscates: Renames classes/methods to short names
• Reduces APK size: Significant size reduction

Q: What are ProGuard/R8 rules?

Rules tell R8 what to keep:

• -keep class com.example.Model: Don't remove or rename
• -keepnames class ...: Don't rename (can still remove if unused)
• -keepclassmembers: Keep members, not class itself

Q: When are keep rules needed?

• Reflection (classes loaded by name)
• Serialization (Gson, JSON parsing)
• JNI (native methods)
• Custom views in XML
• Libraries without rules

Most libraries include their own rules via consumerProguardFiles.

6. Signing

Q: What is APK/AAB signing?

Digital signature that:

• Proves app comes from you
• Ensures APK hasn't been modified
• Required for Play Store and device installation
• Same key required for updates

Q: Debug vs Release signing?

Q: What is Play App Signing?

Google manages your app signing key:

• You upload with upload key
• Google re-signs with app signing key
• If upload key compromised, can reset it
• Key never leaves Google's servers

Recommended for all new apps.

7. Build Performance

Q: How do you speed up Gradle builds?

Q: What is incremental compilation?

Only recompile files that changed. Kotlin supports it, but annotation processors (KAPT) can break it. Consider KSP (Kotlin Symbol Processing) for better incremental support.

Q: How do you analyze build performance?

• ./gradlew --profile: Generate HTML report
• Build Analyzer in Android Studio
• --scan for detailed Gradle build scan
• Check configuration phase time (runs every build)

8. Modularization

Q: Why modularize an Android project?

• Faster builds: Only changed modules rebuild
• Better encapsulation: Clear boundaries, internal visibility
• Parallel development: Teams work independently
• Reusability: Share modules across apps
• Dynamic delivery: Feature modules on demand

Q: What module types exist?

Q: What's dynamic feature delivery?

Feature modules delivered on-demand or by condition:

• Install-time: Included in base APK
• On-demand: Downloaded when needed
• Conditional: Based on device features

Uses App Bundle format, Play Store handles delivery.

Quick Reference