termux-android-hello

Build and install Android APKs entirely from Termux -- no Android Studio, no computer, just your phone.

This is a minimal Hello World app that demonstrates the complete build pipeline: resource compilation, Java compilation, DEX conversion, APK packaging, and signing.

Prerequisites

• Android device with Termux installed
• Java (JDK) installed in Termux: pkg install openjdk-21

Quick Start

# Clone the repo
git clone https://github.com/azmaveth/termux-android-hello.git
cd termux-android-hello

# Install build tools and download android.jar
bash setup.sh

# Grant storage access (needed once for installing APKs)
termux-setup-storage

# Build the APK
bash build.sh

# Install on device
cp build/apk/app.apk ~/storage/shared/ && termux-open ~/storage/shared/app.apk

What setup.sh installs

Package	Purpose
aapt2	Android resource compiler and linker
apksigner	APK signing tool
dx	Java bytecode to DEX converter
zip	APK packaging

It also downloads the Android SDK platform JAR (android.jar from API 33) which provides the Android framework classes, and generates a debug signing keystore.

Build Pipeline

The build follows the standard Android build process, just without Gradle:

res/*.xml ──> aapt2 compile ──> *.flat
                                  │
AndroidManifest.xml ──> aapt2 link ──> unsigned.apk + R.java
                                                        │
*.java + R.java ──> javac ──> *.class ──> dx ──> classes.dex
                                                      │
unsigned.apk + classes.dex ──> zip ──> apksigner ──> signed.apk

Project Structure

.
├── AndroidManifest.xml          # App manifest
├── build.sh                     # Build script
├── setup.sh                     # One-time setup (installs tools)
├── res/
│   ├── layout/activity_main.xml # UI layout
│   └── values/strings.xml       # String resources
└── src/
    └── com/example/hello/
        └── MainActivity.java    # App code

Limitations

• Java 8 bytecode only (uses dx instead of d8 due to a JDK 21 compatibility issue)
• No dependency management (no Gradle/Maven)
• No AndroidX/Jetpack libraries (framework APIs only)
• No ProGuard/R8 minification
• No Compose -- XML layouts only

These limitations aside, this approach works well for utility apps, prototypes, personal tools, and learning Android fundamentals.

Adapting for Your Own App

1. Change the package name in AndroidManifest.xml and the directory structure under src/
2. Update build.sh to point to your new package/class paths
3. Add your layouts in res/layout/ and strings in res/values/
4. Write your Java code -- any Android framework API is available

License

MIT