Cargo NDK for Android projects

Allows building Rust code via cargo ndk command in android projects.

It is somewhat similar to the Mozilla Rust Android Gradle Plugin, however, it uses cargo ndk to find the right linker and ar and build the project. Also, it allows configuring rust release profile (dev vs release) for each gradle buildType. Actually, any options can be configured per gradle buildType, it works similar to android configuration.

Gradle Plugin Page.

Usage

Add the plugin to your root build.gradle, like:

buildscript {
    repositories {
        maven {
            url "https://plugins.gradle.org/m2/"
        }
    }
    dependencies {
        classpath "gradle.plugin.com.github.willir.rust:plugin:0.3.4"
    }
}

In your project's build.gradle, apply plugin and add the cargoNdk configuration (optionally):

android { ... }

apply plugin: "com.github.willir.rust.cargo-ndk-android"

// The following configuration is optional and works the same way by default
cargoNdk {
    buildTypes {
        release {
            buildType = "release"
        }
        debug {
            buildType = "debug"
        }
    }
}

Install rust toolchains:

rustup target add aarch64-linux-android armv7-linux-androideabi i686-linux-android x86_64-linux-android

Install cargo-ndk:

cargo install cargo-ndk

If you already have cargo-ndk, please make sure it is up to date:

cargo install --force cargo-ndk

Next, you need to specify path to NDK via either setting ANDROID_NDK_HOME env variable, or ndk.dir property in local.properties.

This plugin adds the following targets: buildCargoNdkDebug, buildCargoNdkRelease, however, they should be run automatically by building your android project as usual. So:

1. ./gradlew assembleDebug will build dev (debug) profile. Depends on, and so will run buildCargoNdkDebug.
2. ./gradlew assembleRelease will build release profile. Depends on, and so will run buildCargoNdkRelease.

Configuration

All options

cargoNdk {
    // List of all targets
    // By default: ["arm64", "arm", "x86", "x86_64"]
    targets = ["arm64", "arm", "x86", "x86_64"]

    // Path to directory with rust project
    // By default: "app/src/main/rust"
    module = "../rust"

    // Path to rust 'target' dir (the dir where build happens), relative to module
    // By default: "target"
    targetDirectory = "target"

    // List of all library names to copy from target to jniLibs
    // By default parses Cargo.toml and gets all dynamic libraries
    librariesNames = ["libmy_library.so"]

    // The apiLevel to build link with
    // By default: android.defaultConfig.minSdkVersion
    apiLevel = 19

    // Whether to build cargo with --offline flag
    // By default: false
    offline = true

    // The rust profile to build
    // Possible values: "debug", "release", "dev" (an alias for "debug")
    // By default: "release" for release gradle builds,
    //             "debug"   for debug   gradle builds
    buildType = "release"

    // Extra arguments to pass to cargo command
    // By default: []
    extraCargoBuildArguments = ["--offline"]

    // Extra environment variables
    // By default: [:]
    extraCargoEnv = ["foo": "bar"]

    // Whether to pass --verbose flag to cargo command
    // By default: false
    verbose = true
}

As it was already mentioned, any of those options can be configured separately for each buildTypes:

cargoNdk {
    apiLevel = 19  // default

    buildTypes {
        debug {
            apiLevel = 26  // overwrite for debug
        }
    }
}

ANDROID_NDK_HOME env variable

One way to specify path to NDK root for cargo-ndk is to set ANDROID_NDK_HOME. In the most common Linux case, you would need to set it in both ~/.bashrc (for terminal usage) and ~/.profile (for Android Studio usage); read ~/.bashrc vs ~/.profile. I usually have a separate .env_setup file, which is included in both ~/.bashrc and ~/.profile.

Usually, after updating ~/.profile, you need to relogin to see the effect.

Read about ~/.bashrc vs ~/.profile.

ndk.dir in local.properties

Instead of specifying ANDROID_NDK_HOME env variable, you can set ndk.dir in local.properties file.

Specify target via gradle property

You can also compile only one target by specifying the rust-target property to gradle. E.g. to build only arm64 target you can: gradle assembleDebug -Prust-target=arm64. It can be useful during development to speed up each build via not rebuilding targets that are not used during testing.

Troubleshooting

Rust error messages

To get the full error message in Android Studio - select the build tab at the bottom of Android Studio, and then select the topmost error group (Build: failed at); it should show you the full log.