The Krust Architecture

A template for efficient and reliable Android apps that are fun to write.

Main Idea

Kotlin on the outside, Rust on the inside, exchanging messages asynchronously.

Structure the core application logic as an asynchronous agent written in Rust powered by the Tokio runtime.

Structure the presentation logic using a reactive presentation model powered by the modern and officially supported Jetpack Compose framework.

Have them communicate by exchanging messages asynchronously.

Using this template

After cloning the repository, rename all relevant identifiers by running the krustInit task:

$ ./gradlew krustInit --app-id my.app.id --app-name MyApp

Run ./gradlew help --task krustInit for a description of the options available.

After that, the root project will be ready to be imported in Android Studio and the Rust backend ready to be opened in your Rust IDE of choice.

Building

./gradlew assembleDebug

Requirements

Out of the box, the project is configured to build native libraries for the x86 and arm64 architectures (see the cargo section in app/build.gradle.kts) which requires the following toolchains to be installed:

rustup target add i686-linux-android
rustup target add aarch64-linux-android

Tested with

• rustc 1.60.0 (7737e0b5c 2022-04-04)

• Android Studio 2021.1.1

• IntelliJ IDEA 2021.3.3

  • org.rust.lang (0.4.169.4584-213)
  • org.toml.lang (213.5744.224)

Kudos

The Krust architecture is made possible by the following frameworks, libraries and tools:

• Rust Android Gradle Plugin
• Jetpack Compose
• Safe JNI Bindings in Rust
• Tokio asynchronous runtime
• Kotlin Serialization
• serde
• thiserror
• eyre