akavel / hellomello

Experiments with writing Android apps in Nim

HelloWorld.apk built with Nim and no Android Studio

To build the project, you will currently need the following prerequisites:

• Nim compiler
• Go compiler (TODO: remove this dependency — at least provide prebuilt binaries of apksigner)
• Android NDK (the elephant in the room...)
  • standalone toolchain — just download and unpack somewhere, no installation required afterwards (still, ~2.5GB unpacked)
• ...and: NO Java, NO JRE, NO Android Studio, NO Android SDK! 🎉

Build Steps

1. Compile the native JNI code, using Nim + Android NDK:

   $ git clone https://github.com/akavel/hellomello
     # Edit `nim.cfg`: change `--clang.path=...` to a correct path to clang in your Android NDK directory.
     # Also: remove `.cmd` suffixes in `nim.cfg` if you are on Linux.
   $ cd hellomello
   $ nim c --app:lib --os:android --cpu=arm -d:noSignalHandler --hint[CC]:on hello.nim
   $ mkdir lib
   $ mkdir lib/armeabi-v7a
   $ mv libhello.so lib/armeabi-v7a/libhello-mello.so
   $ cd ..
   

2. Assemble the Dalvik bytecode (required to wrap the JNI library), using dali:

   $ git clone https://github.com/akavel/dali
   $ cd dali
   $ nim c jni_hello.nim
   $ ./jni_hello > ../hellomello/classes.dex
   $ cd ..
   

3. Compile the manifest file to binary format, using marco:

   $ git clone https://github.com/akavel/marco
   $ cd marco
   $ nimble build
   $ cd ../hellomello
   $ ../marco/marco < AndroidManifest0.xml > AndroidManifest.xml
   

4. Build an unsigned .apk, using OS-provided zip archiver:

   $ zip -r unsigned.apk  classes.dex lib/ AndroidManifest.xml
     adding: classes.dex (172 bytes security) (deflated 44%)
     adding: lib/ (192 bytes security) (stored 0%)
     adding: lib/armeabi-v7a/ (192 bytes security) (stored 0%)
     adding: lib/armeabi-v7a/libhello-mello.so (172 bytes security) (deflated 60%)
     adding: AndroidManifest.xml (172 bytes security) (stored 0%)
   $ cd ..
   

5. Sign the .apk, using apksigner tool written in Go:

   $ git clone https://github.com/akavel/apksigner
   $ cd apksigner
   $ go build
   $ cd ../hellomello
   $ ../apksigner/apksigner -i unsigned.apk -o hello.apk -k key.pk8 -c key.x509.pem
   $ unzip -l hello.apk
   Archive:  hello.apk
     Length     Date   Time    Name
    --------    ----   ----    ----
         282  00-00-80 00:00   META-INF/MANIFEST.MF
         335  00-00-80 00:00   META-INF/CERT.SF
         436  00-00-80 00:00   META-INF/CERT.EC
          14  06-05-19 22:30   AndroidManifest.xml
        1060  06-05-19 22:29   classes.dex
      149348  06-05-19 22:28   lib/armeabi-v7a/libhello-mello.so
    --------                   -------
      151475                   6 files
   

6. ...aaand you should have a hello.apk file now, ready to be installed on an ARM-based Android device. Worked For Me™... In case of problems installing or opening the apk on your device, try running adb logcat (yep, that requires Android Studio... or you could try python-adb). I suggest searching for "InstallInstall" and "InstallFail" messages, verifier/verification messages, and Java-like exception stack traces. You're welcome to post your problems as issues on this repository, but I can't promise I will be able to help you in any way. We can treat them as "observations" or "reports". Maybe someone else will come by and suggest some steps for future experimenters.

/Mateusz Czapliński.
2019-05-06