Build a minimal Android game APK (like Tetris) from scratch using only Java, Canvas, and android.jar — no Gradle, no Kotlin, no libraries. Result: 16KB APK.

2026-03-2221

name	build-android-apk-without-gradle
description	Build Android APK without Android Studio, Gradle, or internet
version	1
author	Promaster

SKILL: Build Android APK Without Gradle

When to use

Use this skill when you need to build an Android APK on a Linux server WITHOUT Android Studio, WITHOUT Gradle, and WITHOUT internet access to Google/Maven servers.

This skill was born from a real session where all standard approaches failed and the APK was built manually tool by tool.

Tools needed

Tool	Purpose	How to get
`aapt2`	Compile XML resources	`git clone github.com/rendiix/termux-aapt` → prebuilt x86-64 binary
`android.jar`	Android platform API classes	`git clone github.com/Reginer/aosp-android-jar` → pick API level
`ecj.jar`	Java compiler (replaces javac!)	Maven Central: `org.eclipse.jdt:ecj` — user uploads to chat
`d8.jar`	Java .class → DEX format	Android SDK: `build-tools/<ver>/lib/d8.jar` — user uploads
`apksigner.jar`	Sign the APK	Android SDK: `build-tools/<ver>/lib/apksigner.jar` — user uploads
`zipalign`	Align APK bytes	`apt-get install -y zipalign`
`keytool`	Create debug keystore	Bundled with JRE — no install needed
`java` (JRE only)	Run all jar tools	Already on server — verify with `java -version`

Why ECJ instead of javac?

javac is part of the JDK which is often unavailable or broken on restricted servers. ECJ (Eclipse Compiler for Java) is a standalone .jar that does the same job using only JRE. Always use --release 8 flag for Android compatibility — using -8 causes LambdaMetafactory cannot be resolved errors.

Why .aar files contain classes.jar?

Android library packages (.aar) are just ZIP archives. The actual compiled classes live inside as classes.jar. Extract with:

unzip mylib.aar classes.jar -d mylib-extracted/

Find .aar files in user's Gradle cache at:

C:\Users\<name>\.gradle\caches\modules-2\files-2.1\androidx.<lib>\<lib>\<version>\<hash>\<lib>.aar

What can be cloned from GitHub (no auth needed)

# android.jar for all API levels (2.2GB total — use sparse clone for one version)
git clone --depth=1 https://github.com/Reginer/aosp-android-jar.git
# then copy: android-jar/android-34/android.jar

# aapt2 prebuilt binary for Linux x86-64
git clone --depth=1 https://github.com/rendiix/termux-aapt.git
# binary at: termux-aapt/prebuilt-binary/x86-64/aapt2

# gradle-wrapper.jar (needed if using gradlew)
git clone --depth=1 --filter=blob:none --sparse https://github.com/gradle/gradle.git
cd gradle && git sparse-checkout set gradle/wrapper
# jar at: gradle/wrapper/gradle-wrapper.jar

Build steps (in order)

Step 1: Setup directory structure

mkdir -p /home/claude/sdk/platforms/android-34
mkdir -p /home/claude/sdk/build-tools/34.0.0/lib
mkdir -p /home/claude/build/{res,classes,dex,gen,apk,apk_final}
mkdir -p /home/claude/androidx-libs

# Place tools
cp android.jar        /home/claude/sdk/platforms/android-34/
cp d8.jar             /home/claude/sdk/build-tools/34.0.0/lib/
cp apksigner.jar      /home/claude/sdk/build-tools/34.0.0/lib/
cp aapt2              /home/claude/sdk/build-tools/34.0.0/
chmod +x              /home/claude/sdk/build-tools/34.0.0/aapt2

# Required package.xml for the platform
cat > /home/claude/sdk/platforms/android-34/package.xml << 'EOF'
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns2:repository xmlns:ns2="http://schemas.android.com/repository/android/common/02">
<localPackage path="platforms;android-34" obsolete="false">
<type-details xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="ns4:platformType">
<api-level>34</api-level><codename></codename>
</type-details>
<revision><major>3</major></revision>
<display-name>Android SDK Platform 34</display-name>
</localPackage>
</ns2:repository>
EOF

Step 2: Extract classes.jar from .aar files

LIBS=/home/claude/androidx-libs
for lib in appcompat core recyclerview; do
  unzip -o $LIBS/$lib.aar classes.jar -d $LIBS/$lib-extracted/
done

Step 3: Compile XML resources with aapt2

AAPT2=/home/claude/sdk/build-tools/34.0.0/aapt2
ANDROID_JAR=/home/claude/sdk/platforms/android-34/android.jar
PROJ=/path/to/app/src/main
BUILD=/home/claude/build

# Compile all res/ files into a zip
$AAPT2 compile --dir $PROJ/res -o $BUILD/res/compiled.zip

# Link → produces resources.apk + R.java
# IMPORTANT: AndroidManifest.xml MUST have package="com.yourpackage" attribute
$AAPT2 link \
  -o $BUILD/apk/resources.apk \
  -I $ANDROID_JAR \
  --manifest $PROJ/AndroidManifest.xml \
  --java $BUILD/gen \
  --auto-add-overlay \
  $BUILD/res/compiled.zip

Theme pitfall: Theme.AppCompat.* requires androidx jars at link time and will fail. Use built-in Android themes:

<!-- GOOD - works without extra jars -->
<style name="AppTheme" parent="android:Theme.Material.Light.NoActionBar"/>

<!-- BAD - fails at aapt2 link step -->
<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar"/>

Manifest pitfall: aapt2 requires package attribute even though AGP deprecates it:

<manifest xmlns:android="..." package="com.yourpackage">

Step 4: Compile Java with ECJ (not javac!)

ANDROID_JAR=/home/claude/sdk/platforms/android-34/android.jar
LIBS=/home/claude/androidx-libs
BUILD=/home/claude/build

CP="$ANDROID_JAR"
CP="$CP:$LIBS/appcompat-extracted/classes.jar"
CP="$CP:$LIBS/core-extracted/classes.jar"
CP="$CP:$LIBS/recyclerview-extracted/classes.jar"

# Collect ALL java files + generated R.java into one list
find /path/to/app/src/main/java -name "*.java" > /tmp/sources.txt
echo "$BUILD/gen/com/yourpackage/R.java" >> /tmp/sources.txt

# Compile everything in ONE command
# CRITICAL: --release 8 (not -8) to avoid LambdaMetafactory error
# CRITICAL: all files at once so cross-file references resolve
java -jar /home/claude/ecj.jar \
  --release 8 \
  -encoding UTF-8 \
  -bootclasspath $ANDROID_JAR \
  -classpath $CP \
  -d $BUILD/classes \
  @/tmp/sources.txt

Step 5: Convert .class → DEX with d8

BUILD=/home/claude/build
ANDROID_JAR=/home/claude/sdk/platforms/android-34/android.jar

java -cp /home/claude/sdk/build-tools/34.0.0/lib/d8.jar \
  com.android.tools.r8.D8 \
  --output $BUILD/dex \
  --lib $ANDROID_JAR \
  $(find $BUILD/classes -name "*.class")

Step 6: Package APK

BUILD=/home/claude/build
PROJ=/path/to/app/src/main

# Base = resources.apk (already has manifest + compiled resources)
cp $BUILD/apk/resources.apk $BUILD/apk_final/app-unsigned.apk

# Add DEX
cd $BUILD/dex && zip -u $BUILD/apk_final/app-unsigned.apk classes.dex

# Add assets if project has them
cd $PROJ && zip -ur $BUILD/apk_final/app-unsigned.apk assets/

Step 7: Zipalign

zipalign -v 4 \
  /home/claude/build/apk_final/app-unsigned.apk \
  /home/claude/build/apk_final/app-aligned.apk

Step 8: Sign APK

# Create debug keystore (only needed once)
keytool -genkey -v \
  -keystore /home/claude/debug.keystore \
  -alias androiddebugkey \
  -keyalg RSA -keysize 2048 \
  -validity 10000 \
  -storepass android -keypass android \
  -dname "CN=Android Debug,O=Android,C=US"

# Sign
java -jar /home/claude/sdk/build-tools/34.0.0/lib/apksigner.jar sign \
  --ks /home/claude/debug.keystore \
  --ks-key-alias androiddebugkey \
  --ks-pass pass:android \
  --key-pass pass:android \
  --out /home/claude/build/apk_final/app-debug.apk \
  /home/claude/build/apk_final/app-aligned.apk

Files to request from user

If tools are missing, ask the user to upload these files from their Windows PC:

# d8.jar and apksigner.jar:
C:\Users\<name>\AppData\Local\Android\Sdk\build-tools\<version>\lib\d8.jar
C:\Users\<name>\AppData\Local\Android\Sdk\build-tools\<version>\lib\apksigner.jar

# androidx .aar files (find version folders and look for .aar not .pom):
C:\Users\<name>\.gradle\caches\modules-2\files-2.1\androidx.appcompat\appcompat\1.6.1\<hash>\appcompat-1.6.1.aar
C:\Users\<name>\.gradle\caches\modules-2\files-2.1\androidx.recyclerview\recyclerview\1.3.2\<hash>\recyclerview-1.3.2.aar
C:\Users\<name>\.gradle\caches\modules-2\files-2.1\androidx.core\core\<version>\<hash>\core-<version>.aar

# ECJ Java compiler jar (download from search.maven.org → org.eclipse.jdt:ecj):
ecj-<version>.jar

Common errors and fixes

Error	Cause	Fix
`LambdaMetafactory cannot be resolved`	Used `-8` flag in ECJ	Use `--release 8` instead
`R cannot be resolved`	Compiled files separately	Compile ALL java files in ONE ecj command
`Theme.AppCompat not found`	AppCompat theme in aapt2 link	Use `android:Theme.Material.Light.NoActionBar`
`<manifest> must have package attribute`	Removed package from manifest	Add `package="com.yourpackage"` to manifest tag
`@NonNull cannot be resolved`	Missing androidx.annotation jar	Remove all `@NonNull` annotations and imports
`AppCompatActivity cannot be resolved`	Missing appcompat or annotation	Extend plain `Activity` instead
`NotificationCompat cannot be resolved`	Missing appcompat	Use native `Notification.Builder(ctx, channelId)`
`ActivityResultLauncher cannot be resolved`	Missing androidx.activity	Use `startActivityForResult` + `onActivityResult`
`java.lang.Object cannot be resolved`	Wrong bootclasspath syntax	Use `-bootclasspath $ANDROID_JAR` as separate flag
`sdk.dir not found`	Missing local.properties	Create file with `sdk.dir=/path/to/sdk`
Gradle downloads itself and fails	services.gradle.org blocked	Need gradle-wrapper.jar + pre-installed gradle
`duplicate class kotlin.collections`	Kotlin stdlib conflict in Gradle	Add `exclude group: 'org.jetbrains.kotlin', module: 'kotlin-stdlib-jdk7'` to build.gradle