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 (ARM32 is not supported yet)

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

Use tools/cross/install_android_ndk.sh script to prepare Android NDK. This is recommended way to build Android NDK.

Or you can use tools/cross/install_android_sdk.sh script to prepare Android SDK including NDK. You can find NDK in {android-sdk-dir}/ndk/{ndk-version} directory.

CMake 3.6.0 or later is required for Android NDK r26d 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. Please refer to infra/nnfw/cmake/options/options_aarch64-android.cmake for details.

Different from cross build for linux,

NDK_DIR is required

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

Here is an example of using Makefile.

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