Usage

Setting up your environment

Before you can compile for Android, you need to setup your environment. This needs to be done only once per system.

Install rustup.
Run rustup target add arm-linux-androideabi, or any other target that you want to compile to.
Install the Java JDK and Ant (on Ubuntu, sudo apt-get install openjdk-8-jdk ant)
Download and unzip the Android NDK
Download and unzip the Android SDK (under SDK Tools Only at the bottom)
Update the SDK: ./android-sdk-linux/tools/android update sdk -u
Install cargo-apk with cargo install cargo-apk.

Compiling

Run cargo apk.

This will build an Android package in target/android-artifacts/build/bin.

Testing on an Android emulator

Start the emulator, then run:

adb install -r target/your_crate

This will install your application on the emulator.

Interfacing with Android

An application is not very useful if it doesn't have access to the screen, the user inputs, etc.

The android_glue crate provides FFI with the Android environment for things that are not in the stdlib.

How it works

The build process

The build process works by invoking cargo rustc and:

Always compiles your crate as a shared library.
Injects the android_native_app_glue file provided by the Android NDK.
Injects some glue libraries in Rust, which ties the link between android_native_app_glue and the main function of your crate.

This first step outputs a shared library, and is run once per target architecture.

The command then sets up an Android build environment, which includes some Java code, in target/android-artifacts and puts the shared libraries in it. Then it runs ant.