How to Cross-build Runtime for Android

Note: To set up a basic build environment on your development PC, please read the how-to-build-runtime.md document first. The cross build covered in this document assumes that you have an environment in which the native build operates normally without problems.

Supported Architecture : AARCH64 only

Prepare Android NDK

There are two ways to get Android NDK: install Android NDK on your PC or use docker image which already has Android NDK installed.

Install Android NDK

You can use tools/cross/install_android_sdk.sh script to prepare Android SDK including NDK.

$ tools/cross/install_android_sdk.sh --install-dir /path/to/android-sdk

If --install-dir is not specified, Android SDK will be installed in tools/cross/android_sdk.

You can find NDK in {android-sdk-dir}/ndk/{ndk-version} directory.

You can check default install NDK version by running tools/cross/install_android_sdk.sh -h command.

Installed NDK version can be changed by specifying --ndk-version option like below:

$ tools/cross/install_android_sdk.sh --ndk-version {ndk-version} --install-dir /path/to/android-sdk

If you want to install NDK version in existing android sdk directory, you can use --update option like below:

$ tools/cross/install_android_sdk.sh --update --install-dir /path/to/android-sdk

CMake 3.6.0 or later is required for Android NDK r27d CMake support.

Host Environment Requirements

If you want to use docker image, please use infra/docker/android-sdk/Dockerfile of our repository or pull the image nnfw/one-devtools:android-sdk from DockerHub. It includes Android SDK and NDK.

You can build the docker image with following command:

$ docker build -t nnfw/one-devtools:android-sdk -f infra/docker/android-sdk/Dockerfile .

Build

Build and install the runtime

Some tools/libs are still not supported and those are not built by default - mostly due to dependency on HDF5 library.

Different from cross build for linux,

  • Wrapper toolchain file for Android NDK: runtime/infra/cmake/buildtool/cross/toolchain_aarch64-android.cmake

  • ANDROID_NDK environment variable or CMAKE_ANDROID_NDK cmake variable is required

If you are using docker image nnfw/one-devtools:android-sdk, you don’t need to specify above variable because environment variable is already set in the image.

Here is an example of using Makefile.

TARGET_OS=android \
CROSS_BUILD=1 \
ANDROID_NDK=/path/android-sdk/ndk/{ndk-version}/ \
make -f Makefile.template install

Otherwise, you can use command

$ source .venv/bin/activate
(.venv)$ ./nnfw configure \
  -DCMAKE_TOOLCHAIN_FILE=infra/cmake/buildtool/cross/toolchain_aarch64-android.cmake \
  -DCMAKE_ANDROID_NDK=/path/android-sdk/ndk/{ndk-version}
(.venv)$ ./nnfw build
(.venv)$ ./nnfw install --prefix build/onert/out