JNI and Gradle in Android Studio

Question

I m trying to add native code to my app  I have everything in    main jni as it was in my Eclipse project  I have added ndk dir     to my local properties  I haven t done anything else yet  I m not sure what else is actually required  so if I ve missed something let me know   When I try and build I get this error   Execution failed for task   app compileDebugNdk    gt  com android ide common internal LoggedErrorException  Failed to run command       Users me android-ndk-r8e ndk-build NDK PROJECT PATH null  APP BUILD SCRIPT  Users me Project app build ndk debug Android mk APP PLATFORM android-19  NDK OUT  Users me Project app build ndk debug obj  NDK LIBS OUT  Users me Project app build ndk debug lib APP ABI all    Error Code      2   Output      make      No rule to make target   Users me Project webapp build ndk debug  Users me Project app src main jni jni part cpp    needed by   Users me Project app build ndk debug obj local armeabi-v7a objs webapp  Users me Project app src main jni jni part o     Stop    What do I need to do   Android mk   LOCAL PATH      call my-dir   include   CLEAR VARS     OpenCV OPENCV CAMERA MODULES  on OPENCV INSTALL MODULES  on include     OpenCV-2 4 5-android-sdk sdk native jni OpenCV mk  LOCAL MODULE       native part LOCAL SRC FILES    jni part cpp LOCAL LDLIBS     -llog -ldl  include   BUILD SHARED LIBRARY    Application mk   APP STL    gnustl static APP CPPFLAGS    -frtti -fexceptions APP ABI    armeabi armeabi-v7a APP PLATFORM    android-8

User · Answer

My issue on OSX it was gradle version  Gradle was ignoring my Android mk  So  in order to override this option  and use my make instead  I have entered this line      sourceSets main jni srcDirs        inside of the android tag in build gradle   I have wasted lot of time on this

User · Answer

Gradle Build Tools 2 2 0  - The closest the NDK has ever come to being called  magic   In trying to avoid experimental and frankly fed up with the NDK and all its hackery I am happy that 2 2 x of the Gradle Build Tools came out and now it just works  The key is the externalNativeBuild and pointing ndkBuild path argument at an Android mk or change ndkBuild to cmake and point the path argument at a CMakeLists txt build script   android       compileSdkVersion 19     buildToolsVersion  25 0 2       defaultConfig           minSdkVersion 19         targetSdkVersion 19          ndk               abiFilters  armeabi    armeabi-v7a    x86                     externalNativeBuild               cmake                   cppFlags  -std c  11                  arguments  -DANDROID TOOLCHAIN clang                            -DANDROID PLATFORM android-19                            -DANDROID STL gnustl static                            -DANDROID ARM NEON TRUE                            -DANDROID CPP FEATURES exceptions rtti                                     externalNativeBuild           cmake                path  src main jni CMakeLists txt                      ndkBuild                path  src main jni Android mk                        For much more detail check Google s page on adding native code   After this is setup correctly you can   gradlew installDebug and off you go  You will also need to be aware that the NDK is moving to clang since gcc is now deprecated in the Android NDK   Android Studio Clean and Build Integration - DEPRECATED  The other answers do point out the correct way to prevent the automatic creation of Android mk files  but they fail to go the extra step of integrating better with Android Studio  I have added the ability to actually clean and build from source without needing to go to the command-line  Your local properties file will need to have ndk dir  path to ndk  apply plugin   com android application   android       compileSdkVersion 14     buildToolsVersion  20 0 0       defaultConfig           applicationId  com example application          minSdkVersion 14         targetSdkVersion 14          ndk               moduleName  YourModuleName                       sourceSets main           jni srcDirs         This prevents the auto generation of Android mk         jniLibs srcDir  src main libs     This is not necessary unless you have precompiled libraries in your project             task buildNative type  Exec  description   Compile JNI source via NDK             def ndkDir   android ndkDirectory         commandLine   ndkDir ndk-build                    -C   file  src main jni   absolutePath     Change src main jni the relative path to your jni source                  -j   Runtime runtime availableProcessors                     all                    NDK DEBUG 1             task cleanNative type  Exec  description   Clean JNI object files             def ndkDir   android ndkDirectory         commandLine   ndkDir ndk-build                    -C   file  src main jni   absolutePath     Change src main jni the relative path to your jni source                  clean             clean dependsOn  cleanNative       tasks withType JavaCompile            compileTask - gt  compileTask dependsOn buildNative          dependencies       compile  com android support support-v4 20 0 0      The src main jni directory assumes a standard layout of the project  It should be the relative from this build gradle file location to the jni directory   Gradle - for those having issues  Also check this Stack Overflow answer   It is really important that your gradle version and general setup are correct  If you have an older project I highly recommend creating a new one with the latest Android Studio and see what Google considers the standard project  Also  use gradlew  This protects the developer from a gradle version mismatch  Finally  the gradle plugin must be configured correctly   And you ask what is the latest version of the gradle plugin  Check the tools page and edit the version accordingly   Final product -  build gradle     Top-level build file where you can add configuration options common to all sub-projects modules      Running  gradle wrapper  will generate gradlew - Getting gradle wrapper working and using it will save you a lot of pain  task wrapper type  Wrapper        gradleVersion    2 2        Look Google doesn t use Maven Central  they use jcenter now  buildscript       repositories           jcenter             dependencies           classpath  com android tools build gradle 1 2 0              NOTE  Do not place your application dependencies here  they belong            in the individual module build gradle files          allprojects       repositories           jcenter             Make sure gradle wrapper generates the gradlew file and gradle wrapper subdirectory  This is a big gotcha   ndkDirectory  This has come up a number of times  but android ndkDirectory is the correct way to get the folder after 1 1  Migrating Gradle Projects to version 1 0 0  If you re using an experimental or ancient version of the plugin your mileage may vary

User · Answer

In my case  I m on Windows and following the answer by Cameron above only works if you use the full name of the ndk-build which is ndk-build cmd  I have to clean and rebuild the project  then restart the emulator before getting the app to work  Actually I imported the sample HelloJni from NDK  into Android Studio   However  make sure the path to NDK does not contain space   Finally  my build gradle is full listed as below   apply plugin   com android application   android       compileSdkVersion 21     buildToolsVersion  21 1 2       defaultConfig           applicationId  com example hellojni          minSdkVersion 4         targetSdkVersion 4          ndk               moduleName  hello-jni                     testApplicationId  com example hellojni tests          testInstrumentationRunner  android test InstrumentationTestRunner            sourceSets main           jni srcDirs         This prevents the auto generation of Android mk           sourceSets main jni srcDirs              jniLibs srcDir  src main libs     This is not necessary unless you have precompiled libraries in your project             task buildNative type  Exec  description   Compile JNI source via NDK             def ndkDir   android plugin ndkFolder         commandLine   ndkDir ndk-build cmd                    -C   file  src main jni   absolutePath     Change src main jni the relative path to your jni source                  -j   Runtime runtime availableProcessors                     all                    NDK DEBUG 1             task cleanNative type  Exec  description   Clean JNI object files             def ndkDir   android plugin ndkFolder         commandLine   ndkDir ndk-build cmd                    -C   file  src main jni   absolutePath     Change src main jni the relative path to your jni source                  clean             clean dependsOn  cleanNative       tasks withType JavaCompile            compileTask - gt  compileTask dependsOn buildNative            dependencies       compile  com android support support-v4 21 0 3

User · Answer

gradle supports ndk compilation by generating another Android mk file with absolute paths to your sources  NDK supports absolute paths since r9 on OSX  r9c on Windows  so you need to upgrade your NDK to r9    You may run into other troubles as NDK support by gradle is preliminary  If so you can deactivate the ndk compilation from gradle by setting   sourceSets main       jni srcDirs          jniLibs srcDir  src main libs      to be able to call ndk-build yourself and integrate libs from libs    btw  you have any issue compiling for x86   I see you haven t included it in your APP ABI

User · Answer

Android Studio 2 2 came out with the ability to use ndk-build and cMake   Though  we had to wait til 2 2 3 for the Application mk support   I ve tried it  it works   though  my variables aren t showing up in the debugger   I can still query them via command line though   You need to do something like this   externalNativeBuild     ndkBuild          path  Android mk           defaultConfig     externalNativeBuild      ndkBuild         arguments  NDK APPLICATION MK  Application mk        cFlags  -DTEST C FLAG1    -DTEST C FLAG2        cppFlags  -DTEST CPP FLAG2    -DTEST CPP FLAG2        abiFilters  armeabi-v7a    armeabi                 See http   tools android com tech-docs external-c-builds  NB  The extra nesting of externalNativeBuild inside defaultConfig was a breaking change introduced with Android Studio 2 2 Preview 5  July 8  2016   See the release notes at the above link

User · Answer

In the module build gradle  in the task field  I get an error unless I use   def ndkDir   plugins getPlugin  com android application   sdkHandler getNdkFolder     I see people using  def ndkDir   android plugin ndkFolder   and  def ndkDir   plugins getPlugin  com android library   sdkHandler getNdkFolder     but neither of those worked until I changed it to the plugin I was actually importing

[android] JNI and Gradle in Android Studio

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