Android - build separate APKs for different processor architectures

android apk build android-ndk native

I decided to re-post my answer from elsewhere here, so that all of this is on one page for easy access. If this is against SO policies, please tell me and delete this post from here.

Here is my idea on how to create separate APK files for each supported processor architecture:

  1. Build one "fat" APK with any tools you use, containing all native code libraries you support, e.g. armeabi, armeabi-v7a, x86 and mips. I'll call it the 'original' APK file.

  2. Unzip your original APK into an empty folder, with any zip/unzip utility, best use command line tools, so that you could automate it with a shell script or batch file later. Actually, as my sample batch script posted below shows, I just use command line zip/unzip tools to manipulate APKs directly, instead of unzipping them fully, but the effect is the same.

  3. In the folder where original APK was uncompressed to (or in the original .apk/.zip), delete META-INF sub-folder (this contains the signatures, we'll need to re-sign the APK after all the modifications, so the original META-INF must be deleted).

  4. Change to lib sub-folder, and delete the sub-folders for any processor architectures you don't want in the new APK file. For example, leave only 'x86' sub-folder to make an APK for Intel Atom processors.

  5. Important: each APK for a different architecture, must have a different 'versionCode' number in AndroidManifest.xml, and the version code for e.g. armeabi-v7a must be slightly higher than the one for armeabi (read Google directions for creating multiple APKs here: http://developer.android.com/google/play/publishing/multiple-apks.html ). Unfortunately, the manifest file is in a compiled binary form inside the APK. We need a special tool for modifying the versionCode there. See below.

  6. Once the manifest is modified with a new version code, and unnecessary directories and files deleted, re-zip, sign and align your smaller APK (use jarsigner and zipalign tools from Android SDK).

  7. Repeat the process for all other architectures you need to support, creating smaller APK files with slightly different version codes (but the same version name).

The only outstanding issue is the way to modify ‘versionCode’ in binary manifest file. I could not find a solution for this for a long time, so finally had to sit down and crank my own code to do this. As the starting point, I took APKExtractor by Prasanta Paul, http://code.google.com/p/apk-extractor/, written in Java. I’m the old school and still more comfortable with C++, so my little utility program 'aminc' written in C++ is now on GitHub at:

https://github.com/gregko/aminc

I posted the entire Visual Studio 2012 solution there, but the whole program is a single .cpp file which probably can be compiled on any platform. And here is a sample Windows batch script file I use to split my "fat" apk named atVoice.apk into 4 smaller files named atVoice_armeabi.apk, atVoice_armeabi-v7a.apk, atVoice_x86.apk and atVoice_mips.apk. I actually submit these files to Google Play (see my app at https://play.google.com/store/apps/details?id=com.hyperionics.avar) and all works perfectly:

@echo off
REM    My "fat" apk is named atVoice.apk. Change below to whatever or set from %1
set apkfile=atVoice
del *.apk

REM    My tools build atVoice-release.apk in bin project sub-dir. 
REM    Copy it herefor splitting.
copy ..\bin\%apkfile%-release.apk %apkfile%.apk

zip -d %apkfile%.apk META-INF/*

REM ------------------- armeabi ------------------------
unzip %apkfile%.apk AndroidManifest.xml
copy/y %apkfile%.apk %apkfile%.zip
zip -d %apkfile%.zip lib/armeabi-v7a/* lib/x86/* lib/mips/*
aminc AndroidManifest.xml 1
zip -f %apkfile%.zip
ren %apkfile%.zip %apkfile%_armeabi.apk
jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore d:\users\greg\.android\Hyperionics.keystore -storepass MyPass %apkfile%_armeabi.apk MyKeyName
zipalign 4 %apkfile%_armeabi.apk %apkfile%_armeabi-aligned.apk
del %apkfile%_armeabi.apk
ren %apkfile%_armeabi-aligned.apk %apkfile%_armeabi.apk

REM ------------------- armeabi-v7a ---------------------
copy/y %apkfile%.apk %apkfile%.zip
zip -d %apkfile%.zip lib/armeabi/* lib/x86/* lib/mips/*
aminc AndroidManifest.xml 1
zip -f %apkfile%.zip
ren %apkfile%.zip %apkfile%_armeabi-v7a.apk
jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore d:\users\greg\.android\Hyperionics.keystore -storepass MyPass %apkfile%_armeabi-v7a.apk MyKeyName
zipalign 4 %apkfile%_armeabi-v7a.apk %apkfile%_armeabi-v7a-aligned.apk
del %apkfile%_armeabi-v7a.apk
ren %apkfile%_armeabi-v7a-aligned.apk %apkfile%_armeabi-v7a.apk

REM ------------------- x86 ---------------------
copy/y %apkfile%.apk %apkfile%.zip
zip -d %apkfile%.zip lib/armeabi/* lib/armeabi-v7a/* lib/mips/*
aminc AndroidManifest.xml 9
zip -f %apkfile%.zip
ren %apkfile%.zip %apkfile%_x86.apk
jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore d:\users\greg\.android\Hyperionics.keystore -storepass MyPass %apkfile%_x86.apk MyKeyName
zipalign 4 %apkfile%_x86.apk %apkfile%_x86-aligned.apk
del %apkfile%_x86.apk
ren %apkfile%_x86-aligned.apk %apkfile%_x86.apk

REM ------------------- MIPS ---------------------
copy/y %apkfile%.apk %apkfile%.zip
zip -d %apkfile%.zip lib/armeabi/* lib/armeabi-v7a/* lib/x86/*
aminc AndroidManifest.xml 10
zip -f %apkfile%.zip
ren %apkfile%.zip %apkfile%_mips.apk
jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore d:\users\greg\.android\Hyperionics.keystore -storepass MyPass %apkfile%_mips.apk MyKeyName
zipalign 4 %apkfile%_mips.apk %apkfile%_mips-aligned.apk
del %apkfile%_mips.apk
ren %apkfile%_mips-aligned.apk %apkfile%_mips.apk


del AndroidManifest.xml
del %apkfile%.apk
:done

Additional safeguards

I get a few error reports at Google Play developer console, stating that a native method could not be found. Most probably this is caused by the user installing a wrong APK, e.g. Intel or MIPS APK on an ARM device. Added extra code to my app, checking the VersionCode number against Build.CPU_ABI, then displaying an error message in case of mismatch, asking the user to re-install from Google Play (or my own website, where I post a "fat" APK) in such case.

Greg


In this article Android NDK: Version code scheme for publishing APKs per architecture I have found a nice solution to this problem. It consists in adding the following code 

 splits {
    abi {
        enable true
        reset()
        include 'x86', 'armeabi', 'armeabi-v7a'
        universalApk true
    }
}

project.ext.versionCodes = ['armeabi': 1, 'armeabi-v7a': 2, 'arm64-v8a': 3, 'mips': 5, 'mips64': 6, 'x86': 8, 'x86_64': 9]

android.applicationVariants.all { variant ->
    variant.outputs.each { output ->
        output.versionCodeOverride =
            project.ext.versionCodes.get(output.getFilter(
                com.android.build.OutputFile.ABI), 0) * 10000000 + android.defaultConfig.versionCode
    }
}

to the android{...} section of the build.gradle script. If you want to understand the details, I highly recommend to read that article, it is really worth reading.

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