name: android-build
description: Use when building Android apps (Gradle CLI) or ROMs (AOSP, LineageOS). Triggers on "gradle build", "assemble", "AOSP", "LineageOS", "lunch", "mka", "breakfast", "brunch", "compile android", "device tree", "kernel build".

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 += \
    [email protected] \
    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