A note on Android NDK build for CircleCI 2.0

At Sentio, we reach to the point that we have to support our hardware, that is we update firmware from our app. All the native code was compiled with gradle successfully on my machine until I pushed. A question popped up, how it would work on CI since local.properties is ignored from git.

With that being said, the first error message appeared on CI

FAILURE: Build failed with an exception.

* What went wrong:
A problem occurred configuring project ':firmware'.
> NDK not configured. 

After having googled, CirleCI 2.0 currently doesn’t have pre-built NDK which means it’s required to download NDK or use a custom docker image with an NDK image.

1. Download NDK

circleCiEnvironmentSetup.sh

function getAndroidNDK {
  ANDROID_HOME="/opt/android/sdk"
  ANDROID_NDK="$ANDROID_HOME/android-ndk-r16b"
  echo 'export ANDROID_NDK=$ANDROID_HOME/android-ndk-r16b' >> $BASH_ENV
  echo 'export ANDROID_NDK_HOME=$ANDROID_HOME/ndk-bundle/' >> $BASH_ENV

  if [ ! -e ANDROID_NDK ]; then
    cd $ANDROID_HOME
    echo "Downloading NDK..."
    sudo curl -L -o ndk.zip https://dl.google.com/android/repository/android-ndk-r16b-linux-x86_64.zip
    unzip -o -q ndk.zip
    mv android-ndk-r16b ndk-bundle

    echo "Installed Android NDK at $ANDROID_NDK"

    sudo rm ndk.zip
  fi
}

Since the SDK is location in a restricted directory, it is obligatory to add sudo for some operations. The idea of the script is to download the NDK, unzip as ndk-bundle . The most important point to note is the NDK must be located in the SDK. An example on my local machine

ndk.dir=/Users/***/Library/Android/sdk/ndk-bundle
sdk.dir=/Users/***/Library/Android/sdk

Otherwise, you may see a message

NDK is missing a "platforms" directory.
If you are using NDK, verify the ndk.dir is set to a valid NDK directory.  It is currently set to /opt/android/sdk/android-ndk-r16b.
If you are not using NDK, unset the NDK variable from ANDROID_NDK_HOME or local.properties to remove this warning.

Googling in this case does not help me. Some answers are Android Studio 2.3 bug. The others are guide to set up NDK by GUI.

Last but not least, an environment variable must be named ANDROID_NDK_HOME containing the NDK path.

Next step

config.yml

- run:
    name: Install Android NDK
    command: source ./script/circleCiEnvironmentSetup.sh && getAndroidNDK

2. Docker

If you are familiar with Docker or just want to play with it. Your docker file must support both SDK and NDK. It is because I tried to compose with a NDK image

docker:
  - image: circleci/android:api-27-alpha
  - image: circleci/openjdk:8-jdk
  - image: bitriseio/android-ndk:latest

but ended up

If you have your custom image, your config.yml should be

docker:
  - image: path // your path on docker hub

circleci/android:api-27-alpha is removed as well.

An dockerfile example

FROM openjdk:8-jdk

RUN mkdir -p /opt/android-sdk-linux && mkdir -p ~/.android && touch ~/.android/repositories.cfg
WORKDIR /opt

ENV ANDROID_HOME /opt/android-sdk-linux
ENV PATH ${PATH}:${ANDROID_HOME}/tools/bin:${ANDROID_HOME}/platform-tools:${PATH}:${ANDROID_HOME}/tools
ENV ANDROID_NDK /opt/android-ndk-linux
ENV ANDROID_NDK_HOME /opt/android-ndk-linux

RUN apt-get update && apt-get install -y --no-install-recommends \
   unzip \
   wget
RUN cd /opt/android-sdk-linux && \
   wget -q --output-document=sdk-tools.zip https://dl.google.com/android/repository/sdk-tools-linux-3859397.zip && \
   unzip sdk-tools.zip && \
   rm -f sdk-tools.zip && \
   echo y | sdkmanager "build-tools;27.0.3" "platforms;android-27" && \
   echo y | sdkmanager "extras;android;m2repository" "extras;google;m2repository" "extras;google;google_play_services" && \
   sdkmanager "cmake;3.6.4111459"
RUN wget -q --output-document=android-ndk.zip https://dl.google.com/android/repository/android-ndk-r16b-linux-x86_64.zip && \
   unzip android-ndk.zip && \
   rm -f android-ndk.zip && \
   mv android-ndk-r16b android-ndk-linux

Conclusion

After having spent a few hours fixing CircleCI with frustration, even though devOps does not sounds interesting, it was a great experience for me to learn new things. Happy Android coding 🎉🎉🎉🎉🎉 .