Building For Android

Note: These instructions for building Holochain on Android are adapted from here.

In order to get to libraries that can be linked against when building HoloSqape for Android, you basically just need to setup up according targets for cargo.

Given that the Android SDK is installed, here are the steps to setting things up for building:

  1. Install the Android tools:

    a. Install Android Studio b. Open Android Studio and navigate to SDK Tools: - MacOS: Android Studio > Preferences > Appearance & Behaviour > Android SDK > SDK Tools - Linux: Configure (gear) > Appearance & Behavior > System Settings > Android SDK c. Check the following options for installation and click OK: * Android SDK Tools * NDK * CMake * LLDB d. Get a beverage of your choice (or a full meal for that matter) why you wait for the lengthy download

  2. Setup ANDROID_HOME env variable:

On MacOS

export ANDROID_HOME=/Users/$USER/Library/Android/sdk

Linux: (assuming you used defaults when installing Android Studio)

export ANDROID_HOME=$HOME/Android/Sdk
  1. Create standalone NDKs (the commands below put the NDK in your home dir but you can put them where you like):
export NDK_HOME=$ANDROID_HOME/ndk-bundle
cd ~
mkdir NDK
${NDK_HOME}/build/tools/make_standalone_toolchain.py --api 26 --arch arm64 --install-dir NDK/arm64
${NDK_HOME}/build/tools/make_standalone_toolchain.py --api 26 --arch arm --install-dir NDK/arm
${NDK_HOME}/build/tools/make_standalone_toolchain.py --api 26 --arch x86 --install-dir NDK/x86
  1. Add the following lines to your ~/.cargo/config:
[target.aarch64-linux-android]
ar = "<your $HOME value here>/NDK/arm64/bin/aarch64-linux-android-ar"
linker = "<your $HOME value here>/NDK/arm64/bin/aarch64-linux-android-clang"

[target.armv7-linux-androideabi]
ar = "<your $HOME value here>/NDK/arm/bin/arm-linux-androideabi-ar"
linker = "<your $HOME value here>/NDK/arm/bin/arm-linux-androideabi-clang"

[target.i686-linux-android]
ar = "<your $HOME value here>/NDK/x86/bin/i686-linux-android-ar"
linker = "<your $HOME value here>/NDK/x86/bin/i686-linux-android-clang"

(this toml file needs absolute paths, so you need to prefix the path with your home dir).

  1. Now you can add those targets to your rust installation with:
rustup target add aarch64-linux-android armv7-linux-androideabi i686-linux-android

Finally, should now be able to build Holochain for Android with your chosen target, e.g.:

cd <holochain repo>
cargo build --target armv7-linux-androideabi --release

NOTE: there is currently a problem in that wabt (which we use in testing as a dev dependency) won't compile on android, and the cargo builder compiles dev dependencies even though they aren't being used in release builds. Thus as a work around, for the cargo build command above to work, you need to manually comment out the dev dependency section in both core/Cargo.toml and core_api/Cargo.toml


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