📄 DocX Generator for Android

An Android application that generates Microsoft Word (.docx) documents with text and images using a Rust-powered backend. Built with Jetpack Compose and Rust via JNI.

✨ Features

✍️ Multi-line Text Input - Write your content directly in the app
🖼️ Multiple Image Support - Add multiple images from your gallery
👁️ Image Preview - See thumbnail previews of selected images
📁 Custom Save Location - Choose where to save your documents
🚀 Fast Generation - Rust-powered document creation
📂 Auto-Open - Automatically opens generated documents

📱 Screenshots

Main Interface

Editable text field for content input
Horizontal image gallery showing selected images
Add Image button for gallery selection
Generate Document button to create and save .docx files

🛠️ Tech Stack

Frontend (Android)

Kotlin 2.1.0
Jetpack Compose 1.7.6 (Modern declarative UI)
Material Design Components
Coil 2.5.0 (Image loading)
Android SDK 35 (Target), 21 (Minimum)

Backend (Document Generation)

Rust - Core document generation logic
docx-rs 0.2.14 - Word document creation
JNI - Java Native Interface bridge
rifgen - Rust-to-Java code generation

Build Tools

Gradle 8.11.1
Android Gradle Plugin 8.7.3
Cargo (Rust package manager)
Android NDK 29.0.14206865

📋 Requirements

Development Requirements

Essential

JDK 21 - Java Development Kit 21 or higher
Android Studio Hedgehog (2023.1.1) or later
Rust 1.70+ with rustup
Android NDK 29+ installed via Android Studio SDK Manager
Android SDK with API level 35

System Requirements

macOS, Linux, or Windows
8GB RAM minimum (16GB recommended)
10GB free disk space

Runtime Requirements (End Users)

Android 5.0 (Lollipop - API 21) or higher
Storage permission for saving documents
Media permission for selecting images

🚀 Setup & Installation

1. Clone the Repository

git clone https://github.com/yourusername/DocxGenerator.git
cd DocxGenerator

2. Install Rust & Android Targets

# Install Rust (if not already installed)
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

# Add Android targets
rustup target add aarch64-linux-android
rustup target add armv7-linux-androideabi

3. Install Java 21

# macOS (using Homebrew)
brew install openjdk@21

# Linux (Ubuntu/Debian)
sudo apt install openjdk-21-jdk

# Windows
# Download from https://adoptium.net/

4. Configure Android SDK & NDK

Open Android Studio → SDK Manager
Under SDK Platforms, install Android 15.0 (API 35)
Under SDK Tools, install:
- Android SDK Build-Tools 34
- Android SDK Platform-Tools
- NDK (Side by side) - version 29+
- Android SDK Command-line Tools

5. Configure NDK Path

Update docx_lib/.cargo/config.toml with your NDK path:

[target.aarch64-linux-android]
ar = "/path/to/Android/sdk/ndk/29.0.14206865/toolchains/llvm/prebuilt/YOUR-PLATFORM/bin/llvm-ar"
linker = "/path/to/Android/sdk/ndk/29.0.14206865/toolchains/llvm/prebuilt/YOUR-PLATFORM/bin/aarch64-linux-android21-clang"

[target.armv7-linux-androideabi]
ar = "/path/to/Android/sdk/ndk/29.0.14206865/toolchains/llvm/prebuilt/YOUR-PLATFORM/bin/llvm-ar"
linker = "/path/to/Android/sdk/ndk/29.0.14206865/toolchains/llvm/prebuilt/YOUR-PLATFORM/bin/armv7a-linux-androideabi21-clang"

Replace:

/path/to/Android/sdk with your Android SDK location
YOUR-PLATFORM with darwin-x86_64 (macOS), linux-x86_64 (Linux), or windows-x86_64 (Windows)

6. Create `local.properties`

echo "sdk.dir=/path/to/Android/sdk" > local.properties

Replace /path/to/Android/sdk with your actual Android SDK path:

macOS: ~/Library/Android/sdk
Linux: ~/Android/Sdk
Windows: C:\\Users\\YourUsername\\AppData\\Local\\Android\\Sdk

🔨 Building the App

Build Debug APK

# Set Java 21 as active JDK
export JAVA_HOME=/path/to/java-21

# Build using Gradle wrapper
./gradlew assembleDebug

Output location: app/build/outputs/apk/debug/app-debug.apk

Build Release APK

./gradlew assembleRelease

Build from Android Studio

Open the project in Android Studio
File → Project Structure → SDK Location → verify Android SDK and NDK paths
Build → Build Bundle(s) / APK(s) → Build APK(s)

Common Build Issues

Issue: `Unsupported class file major version 68`

Solution: Ensure you're using Java 21

java -version  # Should show version 21
export JAVA_HOME=/path/to/java-21

Issue: `linker 'aarch64-linux-android21-clang' not found`

Solution: Install NDK via Android Studio SDK Manager and update .cargo/config.toml

Issue: `SDK location not found`

Solution: Create local.properties with correct SDK path

📦 Installation (End Users)

Install Pre-built APK

Download docx-generator-debug.apk from Releases
Enable Install from Unknown Sources in Settings
Install the APK
Grant required permissions

Permissions Required

Storage - To save generated .docx files
Media/Photos - To select images from gallery

🎯 Usage

Enter Text - Type your document content in the text field
Add Images - Tap "Add Image" to select from gallery (repeat for multiple images)
Preview - View selected image thumbnails in the horizontal gallery
Generate - Tap "Generate Document"
Choose Location - Select where to save the .docx file
Done! - Document opens automatically

🏗️ Project Structure

DocxGenerator/
├── app/                          # Android app module
│   ├── src/main/
│   │   ├── java/.../MainActivity.kt  # Main UI & logic
│   │   ├── res/                      # Resources
│   │   └── AndroidManifest.xml
│   └── build.gradle              # App dependencies
├── docx_lib/                     # Rust library
│   ├── src/
│   │   ├── lib.rs                # Rust library entry point
│   │   └── docx_glue.rs          # JNI bindings (generated)
│   ├── .cargo/config.toml        # Rust Android build config
│   ├── Cargo.toml                # Rust dependencies
│   └── build.rs                  # Build script
├── releases/                     # Pre-built APKs
│   └── docx-generator-debug.apk
├── build.gradle                  # Root build config
├── settings.gradle               # Project settings
└── README.md                     # This file

🔧 Architecture

High-Level Flow

User Input (Compose UI)
    ↓
MainActivity (Kotlin)
    ↓
JNI Bridge
    ↓
Rust Library (docx_lib)
    ↓
docx-rs (Document Creation)
    ↓
.docx File Output

Key Components

1. MainActivity.kt

Jetpack Compose UI
Text input management
Image selection handling
Document generation coordination

2. AndroidDocBuilder (Rust)

new() - Create document builder
add_text(text) - Add text paragraph
add_image(path, width, height) - Add image
generate_docx(path) - Save document

3. JNI Bridge

Generated by rifgen and flapigen
Provides Kotlin/Java API for Rust functions
Handles memory management across language boundary

🧪 Testing

Run Tests

# Android instrumented tests
./gradlew connectedAndroidTest

# Unit tests
./gradlew test

# Rust tests
cd docx_lib
cargo test

🐛 Troubleshooting

Build Issues

Problem: Gradle sync fails

# Solution: Clear caches
./gradlew clean
rm -rf .gradle .idea build app/build

Problem: Rust compilation fails

# Solution: Clean Rust artifacts
cd docx_lib
cargo clean

Problem: NDK not found

# Solution: Check NDK installation
ls $ANDROID_SDK_ROOT/ndk/
# Update .cargo/config.toml with correct path

Runtime Issues

Problem: App crashes on image selection

Solution: Grant media permissions in Settings

Problem: Document not saving

Solution: Grant storage permissions and ensure valid save location

Problem: Native library not found

Solution: Rebuild app to regenerate .so files

./gradlew clean assembleDebug

🚧 Development

Adding New Features

Modify Rust Library (docx_lib/src/lib.rs)
Rebuild to regenerate JNI bindings
Update UI in MainActivity.kt
Test on device/emulator

Code Style

Kotlin: Follow Android Kotlin style guide
Rust: Run cargo fmt before committing

📝 License

This project is licensed under the MIT License - see the LICENSE file for details.

🤝 Contributing

Contributions are welcome! Please:

Fork the repository
Create a feature branch (git checkout -b feature/amazing-feature)
Commit your changes (git commit -m 'Add amazing feature')
Push to the branch (git push origin feature/amazing-feature)
Open a Pull Request

📧 Support

For issues and questions:

Open an Issue
Check existing Discussions

🙏 Acknowledgments

docx-rs - Rust library for .docx generation
rifgen - Rust JNI bindings generator
Jetpack Compose - Modern Android UI toolkit
Coil - Image loading library

📊 Project Status

Status: Active Development 🚀

Version: 1.0.0

Last Updated: October 2025

Made with ❤️ using Kotlin, Rust, and Jetpack Compose

Name		Name	Last commit message	Last commit date
Latest commit History 9 Commits
.idea		.idea
app		app
docx_lib		docx_lib
gradle/wrapper		gradle/wrapper
releases		releases
.gitignore		.gitignore
README.md		README.md
build.gradle		build.gradle
gradle.properties		gradle.properties
gradlew		gradlew
gradlew.bat		gradlew.bat
settings.gradle		settings.gradle

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