Android studio gradle and NDK

Question

I am very new to this whole gradle and Android Studio support  I have managed to convert my android project to gradle using the export option   But I am looking for some documentation or start point how to integrate the NDK build into the gradle build process    If possible I also need some sort of  after  stage that copies the build binaries   so files  to the asset directory

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UPDATE  The Android Studio with NDK support is out now  http   tools android com tech-docs android-ndk-preview  For building with a script the gradle solution below should work   I am using my build script and added to my file  Seems to work for 0 8    This seems to be equivalent to the solution below  but looks nicer in the gradle file     android       sourceSets           main               jniLibs srcDirs     native-libs               jni srcDirs        disable automatic ndk-build                      The build unfortunately does not fail if the directory is not present or contains no  so files

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configure project in android studio from eclipse  you have to import eclipse ndk project to android studio without exporting to gradle and it works   also you need to add path of ndk in local properties  if shows error then add   sourceSets main           jniLibs srcDir  src main libs           jni srcDirs        disable automatic ndk-build callenter code here         in build gradle file then create jni folder and file using terminal and run it will work

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This is the code i use to build using android-ndk from gradle  For this add ndk directory path in gradle properties ie   add ndkdir  home user android-ndk-r9d and put all jni files in a folder native in src main  as you can see from code posted below  It will create jar with native libs which you can use normally as in System loadLibrary  libraryname     dependencies       compile fileTree dir    buildDir native-libs   include     jar      task ndkBuild type  Exec        commandLine   ndkdir ndk-build    --directory     projectDir src main native    -j   Runtime runtime availableProcessors                 APP PLATFORM android-8                APP BUILD SCRIPT  projectDir src main native Android mk                NDK OUT  buildDir native obj                NDK APP DST DIR  buildDir native libs    TARGET ARCH ABI      task nativeLibsToJar type  Jar  description   create a jar with native libs         destinationDir file   buildDir native-libs       baseName  native-libs      from fileTree dir    buildDir native libs   include        so       into  lib      tasks withType JavaCompile        compileTask - gt  compileTask dependsOn nativeLibsToJar    nativeLibsToJar dependsOn  ndkBuild

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If you re on unix the latest version  0 8  adds ndk-build   Here s how to add it   android ndk       moduleName  libraw      It expects to find the JNI under  src main jni   otherwise you can define it with   sourceSets main       jni srcDirs    path      As of 28 JAN 2014 with version 0 8 the build is broken on windows  you have to disable the build with   sourceSets main       jni srcDirs        disable automatic ndk-build call  currently broken for windows

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Now that Android Studio is in the stable channel  it is pretty straightforward to get the android-ndk samples running   These samples use the ndk experimental plugin and are newer than the ones linked to from the Android NDK online documentation   Once you know they work you can study the build gradle  local properties and gradle-wrapper properties files and modify your project accordingly   Following are the steps to get them working    Go to settings  Appearance  amp  Behavior  System Settings  Android SDK  selected the SDK Tools tab  and check Android NDK version 1 0 0 at the bottom of the list   This will download the NDK  Point to the location of the newly downloaded NDK   Note that it will be placed in the sdk ndk-bundle directory   Do this by selecting File  Project Structure  SDK Location  on left   and supplying a path under Android NDK location   This will add an ndk entry to local properties similar to this        Mac Linux  ndk dir  Android sdk ndk-bundle   Windows  ndk dir C  Android sdk ndk-bundle    I have successfully built and deployed all projects in the repository this way  except gles3gni  native-codec and builder   I m using the following     Android Studio 1 3 build AI-141 2117773 android-ndk samples published July 28  2015  link above  SDK Tools 24 3 3 NDK r10e extracted to C  Android sdk ndk-bundle Gradle 2 5 Gradle plugin 0 2 0 Windows 8 1 64 bit

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A good answer automating the packaging of readily compiled  so-files is given in another  closed  thread  To get that working  I had to change the line   from fileTree dir   libs   include        so     into   from fileTree dir   src main libs   include        so      Without this change the  so files were not found  and the task for packaging them would therefore never run

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To expand on what Naxos said  Thanks Naxos for sending me in the right direction    I learned quite a bit from the recently released NDK examples and posted an answer in a similar question here   How to configure NDK with Android Gradle plugin 0 7  This post has full details on linking prebuilt native libraries into your app for the various architectures as well as information on how to add NDK support directly to the build gradle script   For the most part  you shouldn t need to do the work around zip and copy anymore

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In Google IO 2015  Google announced full NDK integration in Android Studio 1 3  It is now out of preview  and available to everyone  https   developer android com studio projects add-native-code html Old answer  Gradle automatically calls ndk-build if you have a jni directory in your project sources  This is working on Android studio 0 5 9  canary build    Download the NDK  Either add ANDROID NDK HOME to your environment variables or add ndk dir  path to ndk to your local properties in your Android Studio project  This allows Android studio to run the ndk automatically   Download the latest gradle sample projects to see an example of an ndk project   They re at the bottom of the page   A good sample project is ndkJniLib   Copy the gradle build from the NDK sample projects  It ll look something like this  This gradle build creates a different apk for each architecture  You must select which architecture you want using the build variants pane   apply plugin   android   dependencies       compile project   lib      android       compileSdkVersion 19     buildToolsVersion  quot 19 0 2 quot          This actual the app version code  Giving ourselves 100 000 values  0  99999      defaultConfig versionCode   123      flavorDimensions  quot api quot    quot abi quot       productFlavors           gingerbread               flavorDimension  quot api quot              minSdkVersion 10             versionCode   1                   icecreamSandwich               flavorDimension  quot api quot              minSdkVersion 14             versionCode   2                   x86               flavorDimension  quot abi quot              ndk                   abiFilter  quot x86 quot                               this is the flavor part of the version code                 It must be higher than the arm one for devices supporting                both  as x86 is preferred              versionCode   3                   arm               flavorDimension  quot abi quot              ndk                   abiFilter  quot armeabi-v7a quot                            versionCode   2                   mips               flavorDimension  quot abi quot              ndk                   abiFilter  quot mips quot                            versionCode   1                   fat               flavorDimension  quot abi quot                 fat binary  lowest version code to be                the last option             versionCode   0                         make per-variant version code     applicationVariants all   variant - gt             get the version code of each flavor         def apiVersion   variant productFlavors get 0  versionCode         def abiVersion   variant productFlavors get 1  versionCode             set the composite code         variant mergedFlavor versionCode   apiVersion   1000000   abiVersion   100000   defaultConfig versionCode             Note that this will ignore your Android mk and Application mk files  As a workaround  you can tell gradle to disable atuomatic ndk-build call  then specify the directory for ndk sources manually  sourceSets main       jniLibs srcDir  src main libs     use the jni  so compiled from the manual ndk-build command     jni srcDirs        disable automatic ndk-build call    In addition  you ll probably want to call ndk-build in your gradle build script explicitly  because you just disabled the automatic call  task ndkBuild type  Exec       commandLine  ndk-build    -C   file  src main jni   absolutePath    tasks withType JavaCompile        compileTask - gt  compileTask dependsOn ndkBuild

User · Answer

An elegant workaround is shown in https   groups google com d msg adt-dev nQobKd2Gl 8 Z5yWAvCh4h4J   Basically you create a jar which contains  lib armeabi yourlib so  and then include the jar in the build

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I have used ndk dir  usr shareData android-ndk-r11b     path of ndk in local properties file in android studio project  and  add this line    android useDeprecatedNdk true  in gradle properties file in android studio project  More information here  http   tools android com tech-docs android-ndk-preview

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I have used the following code to compile native dropbox libraries  I am using Android Studio v1 1    task nativeLibsToJar type  Zip        destinationDir file   buildDir native-libs       baseName  native-libs      extension  jar      from fileTree dir   src main libs   include        so       into  lib      tasks withType JavaCompile        compileTask - gt  compileTask dependsOn nativeLibsToJar

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If your project exported from eclipse add the codes below in gradle file   android      sourceSets          main             jniLibs srcDir  libs                          2 If you create a project in Android studio   create a folder named jniLibs  in src main     and put your   so files in the jniLibs folder   And copy code as below in your gradle file    android       sourceSets           main             jniLibs srcDir  jniLibs

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The answer from  plaisthos broke in the latest gradle version  but there is still a way to do it  Create a native-libs directory in the root of your project directory and copy all y our libs into this directory   Add the following lines to your build gradle  Build and be happy   task copyNativeLibs type  Copy        from new File project    lt your project gt    getProjectDir     native-libs      include       so        into new File buildDir   native-libs      tasks withType Compile    compileTask - gt  compileTask dependsOn copyNativeLibs    clean dependsOn  cleanCopyNativeLibs

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We have released a first version of the integration as a preview in 1 3  http   tools android com tech-docs android-ndk-preview  The integration will stay a preview even after 1 3 becomes final  No current ETA as to when it ll be final  as of 2015 07 10    More information here  http   tools android com tech-docs android-ndk-preview

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While I believe SJoshi  oracle guy  has the most complete answer  the SWIG project is a special case  interesting and useful one  at that  but not generalized for the majority of projects that have done well with the standard SDK ant based projects   NDK   We all would like to be using Android studio now most likely  or want a more CI friendly build toolchain for mobile  which gradle theoretically offers   I ve posted my approach  borrowed from somewhere  I found this on SO  but posted a gist for the app build gradle  https   gist github com truedat101 c45ff2b69e91d5c8e9c7962d4b96e841     In a nutshell  I recommend the following    Don t upgrade your project to the latest gradle build Use com android tools build gradle 1 5 0 in your Project root Use com android application in your app project Make sure gradle properties has  android useDeprecatedNdk true  in case it s complaining  Use the above approach to ensure that your hours and hours of effort creating Android mk files won t be tossed away   You control which targets arch s  to build   And these instructions are kind to Windows users  who should theoretically be able to build on windows without special issues    Gradle for Android has been a mess in my opinion  much as I like the maven concepts borrowed and the opinionated structure of directories for a project   This NDK feature has been  coming soon  for almost 3  years

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Just add this lines to app build gradle  dependencies               compile fileTree dir    buildDir native-libs   include   native-libs jar      task nativeLibsToJar type  Zip  description   create a jar archive of the native libs         destinationDir file   buildDir native-libs       baseName  native-libs      extension  jar      from fileTree dir   libs   include        so       into  lib armeabi      tasks withType JavaCompile        compileTask - gt  compileTask dependsOn nativeLibsToJar

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As of now  Android Studio v0 8 6  it s quite simple   Here are the steps to create a  Hello world  type app    Download the Android NDK and put the root folder somewhere sane -- in the same location as the SDK folder  perhaps  Add the following to your local properties file  ndk dir  lt path-to-ndk gt  Add the following to your build gradle file inside of the defaultConfig closure  right after the versionName line  ndk   moduleName  hello-world    In your app module s main directory  create a new folder called jni  In that folder  create a file called hello-world c  which you ll see below  See the example Activity code below for an example of how to call a method  or is it a function   in hello-world c      hello-world c   include  lt string h gt   include  lt jni h gt   jstring Java me mattlogan ndktest MainActivity stringFromJNI JNIEnv  env  jobject thiz        return   env - gt NewStringUTF env   Hello world           MainActivity java  public class MainActivity extends Activity        static           System loadLibrary  hello-world               public native String stringFromJNI          Override     protected void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout activity main            String testString   stringFromJNI             TextView mainText    TextView  findViewById R id main text           mainText setText testString               build gradle  apply plugin   com android application   android       compileSdkVersion 20     buildToolsVersion  20 0 0       defaultConfig           applicationId  me mattlogan ndktest          minSdkVersion 15         targetSdkVersion 20         versionCode 1         versionName  1 0           ndk               moduleName  hello-world                      buildTypes           release               runProguard false             proguardFiles getDefaultProguardFile  proguard-android txt     proguard-rules pro                     dependencies       compile fileTree dir   libs   include      jar          Find the full source code of a very similar app here  minus the NDK

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I found  gradle 1 11 com android tools build gradle 0 9    supports pre-build ndk now  you can just put the   so in the dir src main jniLibs  when building gradle will package the ndk to the right place   here is my project   Project   --src  -- --main  -- -- --java  -- -- --jniLibs  -- -- -- --armeabi  -- -- -- -- -- so files  --libs  -- --other jar

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With the update of Android Studio to 1 0  the NDK toolchain support improved immensely  note  please read my updates at the bottom of this post to see usage with the new experimental Gradle plugin and Android Studio 1 5    Android Studio and the NDK are integrated well enough so that you just need to create an ndk   block in your module s build gradle  and set your source files into the  module  src main jni directory - and you re done    No more ndk-build from the command line   I ve written all about it in my blog post here  http   www sureshjoshi com mobile android-ndk-in-android-studio-with-swig   The salient points are      There are two things you need to know here  By default  if you have external libs that you want loaded into the Android application  they are looked for in the  module  src main jniLibs by default  You can change this by using setting sourceSets main jniLibs srcDirs in your module   s build gradle  You   ll need a subdirectory with libraries for each architecture you   re targeting  e g  x86  arm  mips  arm64-v8a  etc          The code you want to be compiled by default by the NDK toolchain will be located in  module  src main jni and similarly to above  you can change it by setting sourceSets main jni srcDirs in your module   s build gradle   and put this into your module s build gradle   ndk     moduleName  SeePlusPlus     Name of C   module  i e  libSeePlusPlus    cFlags  -std c  11 -fexceptions     Add provisions to allow C  11 functionality   stl  gnustl shared     Which STL library to use  gnustl or stlport     That s the process of compiling your C   code  from there you need to load it  and create wrappers - but judging from your question  you already know how to do all that  so I won t re-hash   Also  I ve placed a Github repo of this example here  http   github com sureshjoshi android-ndk-swig-example  UPDATE  June 14  2015  When Android Studio 1 3 comes out  there should be better support for C   through the JetBrains CLion plugin  I m currently under the assumption that this will allow Java and C   development from within Android Studio  however I think we ll still need to use the Gradle NDK section as I ve stated above  Additionally  I think there will still be the need to write Java lt - C   wrapper files  unless CLion will do those automatically   UPDATE  January 5  2016  I have updated my blog and Github repo  in the develop branch  to use Android Studio 1 5 with the latest experimental Gradle plugin  0 6 0-alpha3    http   www sureshjoshi com mobile android-ndk-in-android-studio-with-swig  http   github com sureshjoshi android-ndk-swig-example  The Gradle build for the NDK section now looks like this   android ndk       moduleName    SeePlusPlus     Name of C   module  i e  libSeePlusPlus      cppFlags add  -std c  11      Add provisions to allow C  11 functionality     cppFlags add  -fexceptions       stl    gnustl shared     Which STL library to use  gnustl or stlport     Also  quite awesomely  Android Studio has auto-complete for C  -Java generated wrappers using the  native  keyword     However  it s not completely rosy    If you re using SWIG to wrap a library to auto-generate code  and then try to use the native keyword auto-generation  it will put the code in the wrong place in your Swig  wrap cxx file    So you need to move it into the  extern C  block     UPDATE  October 15  2017  I d be remiss if I didn t mention that Android Studio 2 2 onwards has essentially  native   no pun  support for the NDK toolchain via Gradle and CMake  Now  when you create a new project  just select C   support and you re good to go    You ll still need to generate your own JNI layer code  or use the SWIG technique I ve mentioned above  but the scaffolding of a C   in Android project is trivial now   Changes in the CMakeLists file  which is where you place your C   source files  will be picked up by Android Studio  and it ll automatically re-compile any associated libraries

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Here are the steps that I used to get the NDK working in my Android Studio project  I used this tutorial to help me out  https   software intel com en-us videos using-the-ndk-with-android-studio  In order to use NDK you must add a NDK line to local properties   So under your sdk dir add  ndk dir C    MyPathToMyNDK ndk   In my apps build gradle I have the following code          ndk               moduleName  myLib              ldLibs  log              stl  gnustl shared              cFlags  -std c  11 -frtti -fexceptions -pthread              moduleName is the name you want to give your native code  I believe this is what the shared library will be called  ldLibs allows me to log to LogCat  stl is the stl that you want to import  There are lots of options  same as the Eclipse NDK    http   www kandroid org ndk docs CPLUSPLUS-SUPPORT html   cFlags are still a certain amount of black magic for me  I have not found a good source for all the options and what they give me  Search around StackOverflow for anything you need  that is where I found it   I do know that the c  11 allows me to use the new c   11 standard   Here is an example of how I log to LogCat from the native code    android log print ANDROID LOG DEBUG   TestApp    Adding - String  d has a field name of  s and a value of  s   i  lKeyUTF8 c str    lValueUTF8 c str

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As Xavier said  you can put your prebuilts in  src main jniLibs  if you are using gradle 0 7 2   taken from  https   groups google com d msg adt-dev nQobKd2Gl 8 ctDp9viWaxoJ

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now I can load the so success   1 add the  so file to this path  Project     --src  -- --main  -- -- --java  -- -- --jniLibs  -- -- -- --armeabi  -- -- -- -- -- so files  2 add this code to gradle build   android   splits       abi           enable true         reset           include  x86    x86 64    arm64-v8a    armeabi-v7a    armeabi          universalApk false              3 System loadLibrary  yousoname      goodluck for you it is ok with gradle 1 2 3

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NDK Builds and gradle  basic   Generally building with the NDK is as simple as correctly specifying an ndkBuild path to Android mk or cmake path to CMakeLists txt  I recommend CMake over the older Android mk because Android Studio s C C   support is based upon CLion and it uses CMake as its project format  This in my experience has tended to make the IDE more responsive on larger projects  Everything compiled in your project will be built and copied into the APK automatically   apply plugin   com android library   android       compileSdkVersion 19     buildToolsVersion  25 0 2       defaultConfig           minSdkVersion 19         targetSdkVersion 19          ndk               abiFilters  armeabi    armeabi-v7a    x86                 64-bit support requires an Android API level higher than 19  Namely 21 and higher               abiFilters  armeabi    armeabi-v7a    arm64-v8a    x86    x86 64                     externalNativeBuild               cmake                   arguments  -DANDROID TOOLCHAIN clang                            -DANDROID PLATFORM android-19                            -DANDROID STL gnustl static                            -DANDROID ARM NEON TRUE                                      externalNativeBuild           cmake               path  src main jni CMakeLists txt                     dependencies       compile fileTree dir   libs   include      jar        Adding prebuilt libraries to the project  advanced   Static libraries   a  in your NDK build will automatically be included  but prebuilt dynamic libraries   so  will need to be placed in jniLibs  This can be configured using sourceSets  but you should adopt the standard  You DO NOT NEED any additional commands in build gradle when including prebuilt libraries   The layout of jniLibs  You can find more information about the structure in the Android Gradle Plugin User Guide     --app   -- --build gradle  -- --src   -- -- --main  -- -- -- --java  -- -- -- --jni  -- -- -- -- --CMakeLists txt  -- -- -- --jniLibs  -- -- -- -- --armeabi  -- -- -- -- -- -- so Files  -- -- -- -- --armeabi-v7a  -- -- -- -- -- -- so Files  -- -- -- -- --x86  -- -- -- -- -- -- so Files    You can then validate the resulting APK contains your  so files  typically under build outputs apk   using unzip -l myApp apk to list the contents   Building shared libraries  If you re building a shared library in the NDK you do not need to do anything further  It will be correctly bundled in the APK

[android] Android studio, gradle and NDK

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