goandroid

Patches to the Go tools and runtime to enable Android apps to interface directly with a shared library written in Go. Goandroid also includes a simple demo written in Go, showing off OpenGL ES 2 and touch input.

Running Go code from Android apps is currently not possible, because the Go tools can only output executables while Android requires any foreign code in shared library (.so) format. This repository contains patches for the Go tools and runtime to enable shared library output, including workarounds to Android specific limitations. It also includes a simple example app written in Go to demonstrate OpenGL ES 2 graphics and touch input.

This guide assumes you're running linux and have an android device connected through USB.

Set up

1. Make sure mercurial is installed

2. Download and install the NDK. These instructions assumes the NDK is installed in $NDK.

3. Create a standalone NDK toolchain (as described in $NDK/docs/STANDALONE-TOOLCHAIN.html):

   $NDK/build/tools/make-standalone-toolchain.sh --platform=android-9 --install-dir=ndk-toolchain

   You might need to add --system=linux-x86_64 or --system=darwin-x86_64 depending on your system.

   Set $NDK_TOOLCHAIN to point at the ndk-toolchain directory

4. Clone the golang repository:

   hg clone https://code.google.com/p/go

5. Copy the patches directory to the go/.hg directory:

   cp -a patches go/.hg

6. Enable the mq extension by adding the following lines to go/.hg/hgrc:

   [extensions]  
   mq =  
   
   [ui]  
   username = me<me@mail.com>
   

7. In the go/src directory apply the patches and build go:

   cd go/src  
   hg qpush -a  
   CGO_ENABLED=0 GOARCH=arm ./make.bash  
   CC="$NDK_TOOLCHAIN/bin/arm-linux-androideabi-gcc" GOARCH=arm GOARM=7 CGO_ENABLED=1 ../bin/go install -tags android -a -v std  
   cd ../..
   

Building and installing the example app

If everything is set up correctly, you should be able to run build.sh in the goandroid root to build and copy libandroid.so to android/libs. Then, running ant -f android/build.xml clean debug install will build and install the final apk to the connected device. Running the app should display a simple color animated triangle that you can move around the screen with your finger.

Go patches

All patches except android-tls and android-build-hacks correspond to the patches for linux/arm external linking and shared library support discussed on the golang-nuts mailing list.

The android-tls patch is a workaround for the missing support for the R_ARM_TLS_IE32 relocation in the Android linker.

The android-build-hacks patch contains various changes to account for the difference between a vanilla linux/arm system and Android.