Android Build Systems

This skill covers building Android apps via Gradle CLI and building custom ROMs via AOSP/LineageOS.

App Building (Gradle CLI)

Essential Commands

./gradlew tasks                     # List available tasks
./gradlew assembleDebug             # Build debug APK
./gradlew assembleRelease           # Build release APK
./gradlew installDebug              # Build + install to device
./gradlew bundleRelease             # Build AAB (App Bundle)

# APK output location
# app/build/outputs/apk/debug/app-debug.apk
# app/build/outputs/apk/release/app-release.apk

Build Variants

./gradlew assembleFreeDebug         # Flavor + build type
./gradlew assemblePaidRelease
./gradlew assembleDebug --info      # Verbose output
./gradlew assembleRelease -x test   # Skip tests

Testing

./gradlew test                      # Unit tests
./gradlew testDebugUnitTest         # Debug unit tests only
./gradlew connectedAndroidTest      # Instrumented tests
./gradlew connectedCheck            # All connected tests

# Run specific test
./gradlew test --tests "*.MyTestClass"

Linting & Analysis

./gradlew lint                      # Run lint
./gradlew lintDebug                 # Debug only (faster)
./gradlew ktlintCheck               # Kotlin style (if configured)
./gradlew detekt                    # Detekt analysis (if configured)

Clean & Refresh

./gradlew clean                     # Clean build
./gradlew clean assembleDebug       # Clean + build
./gradlew --refresh-dependencies    # Force dependency refresh
./gradlew --stop                    # Stop Gradle daemon

Dependencies

./gradlew dependencies              # All dependencies
./gradlew app:dependencies          # Module dependencies
./gradlew dependencyInsight --dependency <name>

Signing

Debug keystore location:

• Linux: ~/.android/debug.keystore
• macOS: ~/.android/debug.keystore
• Windows: C:\Users\<user>\.android\debug.keystore

Password: android, Alias: androiddebugkey

# Create release keystore
keytool -genkey -v -keystore release.keystore \
    -alias my-key-alias -keyalg RSA -keysize 2048 -validity 10000

Performance

./gradlew assembleDebug --parallel  # Parallel builds
./gradlew assembleDebug --build-cache  # Use cache
./gradlew assembleDebug --offline   # Offline mode
./gradlew --scan                    # Build scan (uploads data)
./gradlew --profile                 # Local profile report

gradle.properties Optimization

org.gradle.jvmargs=-Xmx4g -XX:+HeapDumpOnOutOfMemoryError
org.gradle.parallel=true
org.gradle.caching=true
org.gradle.configuration-cache=true
android.useAndroidX=true

SDK Management

sdkmanager

sdkmanager --list                   # List available packages
sdkmanager --list | grep system     # Filter system images
sdkmanager "platform-tools"         # Install package
sdkmanager "platforms;android-34"   # Install platform
sdkmanager "system-images;android-34;google_apis;x86_64"
sdkmanager --update                 # Update all
sdkmanager --licenses               # Accept licenses

avdmanager

avdmanager list device              # List device profiles
avdmanager list avd                 # List created AVDs

# Create AVD
avdmanager create avd -n my_avd \
    -k "system-images;android-34;google_apis;x86_64" \
    -d pixel_6

avdmanager delete avd -n my_avd

Emulator CLI

emulator -list-avds                 # List AVDs
emulator @my_avd                    # Start AVD
emulator @my_avd -no-snapshot       # Fresh boot
emulator @my_avd -no-window         # Headless
emulator @my_avd -wipe-data         # Factory reset

ROM Building (AOSP/LineageOS)

Environment Setup

# Install repo tool
mkdir -p ~/.bin
curl https://storage.googleapis.com/git-repo-downloads/repo > ~/.bin/repo
chmod a+x ~/.bin/repo
export PATH="$HOME/.bin:$PATH"

# Initialize repo
mkdir android && cd android
repo init -u https://github.com/LineageOS/android.git -b lineage-21.0
# Or AOSP: repo init -u https://android.googlesource.com/platform/manifest

# Sync source
repo sync -c -j$(nproc) --force-sync --no-tags --no-clone-bundle

Build Commands

# Setup environment
source build/envsetup.sh

# Select device
lunch <device>-userdebug           # AOSP
breakfast <device>                  # LineageOS

# Build
m                                   # Full build
mka bacon                           # LineageOS (with flashable zip)
mka bootimage                       # Just boot.img
mka systemimage                     # Just system

# Parallel build
m -j$(nproc)

Build Variants

Common Targets

m bootimage                         # Kernel + ramdisk
m systemimage                       # System partition
m vendorimage                       # Vendor partition
m otapackage                        # OTA zip
mka bacon                           # LineageOS flashable zip

# Module-specific
m Settings                          # Just Settings app
mm                                  # Build current directory
mmm packages/apps/Settings          # Build specific path

LineageOS Specifics

breakfast <device>                  # Setup + sync device deps
brunch <device>                     # breakfast + mka bacon

# Cherry-pick from Gerrit
repopick <change_number>
repopick -t <topic>

# Sync specific project
repo sync packages/apps/Settings

Build Output

out/target/product/<device>/
├── boot.img                        # Kernel + ramdisk
├── system.img                      # System partition
├── vendor.img                      # Vendor partition
├── lineage-*.zip                   # Flashable zip (LineageOS)
└── recovery.img                    # Recovery (non-A/B)

Device Trees

Structure

device/<vendor>/<device>/
├── AndroidProducts.mk              # Product makefiles list
├── BoardConfig.mk                  # Board configuration
├── device.mk                       # Device makefile
├── lineage_<device>.mk             # LineageOS product
├── extract-files.sh                # Vendor blob extraction
├── proprietary-files.txt           # Blob list
├── sepolicy/                       # SELinux policies
└── overlay/                        # Resource overlays

Key Files

BoardConfig.mk - Hardware configuration:

TARGET_ARCH := arm64
TARGET_BOARD_PLATFORM := <platform>
TARGET_BOOTLOADER_BOARD_NAME := <device>
BOARD_KERNEL_CMDLINE := ...
BOARD_BOOT_HEADER_VERSION := 4

device.mk - Device packages:

PRODUCT_PACKAGES += \
    android.hardware.audio@7.0-impl \
    audio.primary.$(TARGET_BOARD_PLATFORM)

PRODUCT_COPY_FILES += \
    $(LOCAL_PATH)/configs/audio_policy.conf:...

Kernel Building

Standalone

# Setup
export ARCH=arm64
export CROSS_COMPILE=aarch64-linux-gnu-
# Or for Clang:
export CC=clang
export CLANG_TRIPLE=aarch64-linux-gnu-

# Configure
make <device>_defconfig

# Build
make -j$(nproc)

# Output
arch/arm64/boot/Image.gz

In AOSP Tree

# In BoardConfig.mk
TARGET_KERNEL_SOURCE := kernel/<vendor>/<device>
TARGET_KERNEL_CONFIG := <device>_defconfig
TARGET_KERNEL_CLANG_COMPILE := true

Troubleshooting

Common Gradle Issues

# OOM
export GRADLE_OPTS="-Xmx4g"

# Daemon issues
./gradlew --stop
rm -rf ~/.gradle/daemon

# Cache issues
./gradlew clean --refresh-dependencies

Common AOSP Issues

# Ninja error - usually dependency issue
m clean && m

# Jack server (old builds)
./prebuilts/sdk/tools/jack-admin kill-server
./prebuilts/sdk/tools/jack-admin start-server

# SELinux issues
audit2allow -i audit.log

Build Logs

# Gradle
./gradlew assembleDebug --stacktrace
./gradlew assembleDebug --info

# AOSP
m 2>&1 | tee build.log

Quick Reference

Gradle

AOSP/LineageOS