Develop Reference

incompatible target while building apk for Native Android Project

I am trying to implement Alexa Voice Service SDK in Android.
I have pre-build libraries, which i am using in my Android Project.
I have .so files under src/main/jniLibs/armeabi-v7a/*.so
I can successfully compile and build apk for x86 platform , but my target is run it on armeabi-v7a device.
but while generating apk i am facing the incompatible target error.
the full error is shown below ,
FAILURE: Build failed with an exception.
What went wrong:
Execution failed for task ':app:externalNativeBuildDebug'.
> Build command failed.
Error while executing process /home/ajinkya/Androidsdk/cmake/3.10.2.4988404/bin/cmake with arguments {--build /root/AndroidStudioProjects/alexaProtoApp/app/.externalNativeBuild/cmake/debug/armeabi-v7a --target native-lib}
[1/2] Building CXX object CMakeFiles/native-lib.dir/native-lib.cpp.o
[2/2] Linking CXX shared library /root/AndroidStudioProjects/alexaProtoApp/app/build/intermediates/cmake/debug/obj/armeabi-v7a/libnative-lib.so
FAILED: /root/AndroidStudioProjects/alexaProtoApp/app/build/intermediates/cmake/debug/obj/armeabi-v7a/libnative-lib.so
: && /home/ajinkya/Androidsdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++ --target=armv7-none-linux-androideabi24 --gcc-toolchain=/home/ajinkya/Androidsdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64 --sysroot=/home/ajinkya/Androidsdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/sysroot -fPIC -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -fno-addrsig -march=armv7-a -mthumb -Wa,--noexecstack -Wformat -Werror=format-security -O0 -fno-limit-debug-info -Wl,--exclude-libs,libgcc.a -Wl,--exclude-libs,libatomic.a -static-libstdc++ -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--exclude-libs,libunwind.a -Wl,--no-undefined -Qunused-arguments -Wl,-z,noexecstack -shared -Wl,-soname,libnative-lib.so -o /root/AndroidStudioProjects/alexaProtoApp/app/build/intermediates/cmake/debug/obj/armeabi-v7a/libnative-lib.so CMakeFiles/native-lib.dir/native-lib.cpp.o /root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/../../main/jniLibs/armeabi-v7a/libSampleApp.so /home/ajinkya/Androidsdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/arm-linux-androideabi/24/liblog.so /home/ajinkya/Androidsdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/arm-linux-androideabi/24/liblog.so -latomic -lm && :
/home/ajinkya/Androidsdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/lib/gcc/arm-linux-androideabi/4.9.x/../../../../arm-linux-androideabi/bin/ld: error: /root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/../../main/jniLibs/armeabi-v7a/libSampleApp.so: incompatible target
/root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/native-lib.cpp:25: error: undefined reference to 'my_initialize(_JavaVM*, _jobject*)'
/root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/native-lib.cpp:31: error: undefined reference to 'jni_wakeAlexa()'
/root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/native-lib.cpp:37: error: undefined reference to 'jni_wakeWithHoldAlexa()'
/root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/native-lib.cpp:43: error: undefined reference to 'jni_resetAlexa()'
/root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/native-lib.cpp:49: error: undefined reference to 'jni_reauthorizeAlexa()'
/root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/native-lib.cpp:55: error: undefined reference to 'jni_quitAlexa()'
/root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/native-lib.cpp:61: error: undefined reference to 'jni_infoAlexa()'
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.
My build.gradle like,
apply plugin: 'com.android.application'
android {
compileSdkVersion 29
defaultConfig {
applicationId "my.project.vdi"
minSdkVersion 24
targetSdkVersion 29
versionCode 1
versionName "1.0"
testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
multiDexEnabled true
externalNativeBuild {
cmake {
cppFlags ""
// abiFilters "armeabi-v7a"
// arguments "-DANDROID_ARM_MODE=arm" , "-DANDROID_TOOLCHAIN=clang"
}
}
ndk {
// Specifies the ABI configurations of your native
// libraries Gradle should build and package with your APK. , x86 , armeabi-v7a
abiFilters "armeabi-v7a"
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
}
}
externalNativeBuild {
cmake {
path "src/main/cpp/CMakeLists.txt"
version "3.10.2"
}
}
sourceSets {
main {
jni.srcDirs = []
// let gradle pack the shared library into apk
jniLibs.srcDirs = ['src/main/jniLibs/']
}
}
// packagingOptions {
// exclude 'lib/arm64-v8a/libnative-lib.so'
// exclude 'lib/x86_64/libnative-lib.so'
// exclude 'lib/x86/libnative-lib.so'
// }
}
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
implementation 'androidx.appcompat:appcompat:1.0.2'
implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'androidx.test:runner:1.2.0'
androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
implementation 'com.squareup.picasso:picasso:2.5.2'
}
ALso the CMakeLists.txt
cmake_minimum_required(VERSION 3.4.1)
add_library( # Sets the name of the library.
native-lib
SHARED
native-lib.cpp)
add_library(SampleApp SHARED IMPORTED)
set_target_properties(SampleApp PROPERTIES IMPORTED_LOCATION ${PROJECT_SOURCE_DIR}/../../main/jniLibs/${ANDROID_ABI}/libSampleApp.so)
find_library(
log-lib
log)
find_library(ANDROID_LOG_LIB log)
target_link_libraries(
native-lib
SampleApp
${ANDROID_LOG_LIB}
${log-lib} )
Please guide me resolving this issue.

.../armeabi-v7a/libSampleApp.so: incompatible target
That library isn't actually built for armeabi-v7a. The following should tell you what it is:
$ file /root/AndroidStudioProjects/alexaProtoApp/app/src/main/cpp/../../main/jniLibs/armeabi-v7a/libSampleApp.so
Here's example output from libc++_shared.so in the NDK:
$ file android-ndk-r21-canary/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/arm-linux-androideabi/libc++_shared.so
android-ndk-r21-canary/toolchains/llvm/prebuilt/linux-x86_64/sysroot/usr/lib/arm-linux-androideabi/libc++_shared.so: ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV), dynamically linked, BuildID[sha1]=4dc00a833014c1ddd2e1ec64c5dd72237c4179ee, with debug_info, not stripped
The interesting part is:
ELF 32-bit LSB shared object, ARM, EABI5 version 1 (SYSV)

I got the solution, it is very unusual for me , the .so files which were generating while compiling, were not getting replaced. the old version of the files were not getting updated by the new ones. I deleted the folder and then compiled and the new files generated were the proper ones.

android studio with opencv libraries linking error

I should say that I'm first time at android studio with ndk.
environment is Android Studio 3.1.4 and OpenCV 3.4 at windows 10 os.
I use open source about opencv that 'Facetracker' link is below
https://github.com/kylemcdonald/FaceTracker
i changed some codes and want to build at android studio
so i drew up CMakeList.txt, Android.mk, Application.mk, build.gradle.
Synchronization with gradle work well but build, generate signed APK occur error below.
Build command failed.
Error while executing process C:\Users\Duru\AppData\Local\Android\Sdk\cmake\3.6.4111459\bin\cmake.exe with arguments {--build D:\ProgramFiles\Android\Projects\OpencvTest\app\.externalNativeBuild\cmake\release\x86_64 --target PAW}
[1/1] **Linking CXX shared library** ..\..\..\..\build\intermediates\cmake\release\obj\x86_64\libPAW.so
FAILED: cmd.exe /C "cd . && C:\Users\Duru\AppData\Local\Android\Sdk\ndk-bundle\toolchains\x86_64-4.9\prebuilt\windows-x86_64\bin\x86_64-linux-android-g++.exe --sysroot=C:/Users/Duru/AppData/Local/Android/Sdk/ndk-bundle/sysroot -fPIC -isystem C:/Users/Duru/AppData/Local/Android/Sdk/ndk-bundle/sysroot/usr/include/x86_64-linux-android -D__ANDROID_API__=21 -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -Wa,--noexecstack -Wformat -Werror=format-security -frtti -fexceptions -std=gnu++11 -O2 -DNDEBUG -Wl,--exclude-libs,libgcc.a -Wl,--exclude-libs,libatomic.a --sysroot C:/Users/Duru/AppData/Local/Android/Sdk/ndk-bundle/platforms/android-21/arch-x86_64 -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-undefined -Wl,-z,noexecstack -Wl,-z,relro -Wl,-z,now -shared -Wl,-soname,libPAW.so -o ..\..\..\..\build\intermediates\cmake\release\obj\x86_64\libPAW.so CMakeFiles/PAW.dir/src/main/jni/src/lib/PAW.cc.o -latomic -lm "C:/Users/Duru/AppData/Local/Android/Sdk/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/libs/x86_64/libgnustl_static.a" && cd ."
D:/ProgramFiles/Android/Projects/OpenCV-android-sdk/sdk/native/jni/include/opencv2/core/cvstd.hpp:648: error: undefined reference to 'cv::String::deallocate()'
**D:/ProgramFiles/Android/Projects/OpenCV-android-sdk/sdk/native/jni/include/opencv2/core/cvstd.hpp:648: error: undefined reference to 'cv::String::deallocate()'
D:/ProgramFiles/Android/Projects/OpenCV-android-sdk/sdk/native/jni/include/opencv2/core/mat.inl.hpp:2686: error: undefined reference to 'cv::MatConstIterator::seek(long, bool)'
D:\ProgramFiles\Android\Projects\OpencvTest\app\src\main\jni\src\lib/PAW.cc:146: error: undefined reference to 'cv::Mat::zeros(int, int, int)'
D:/ProgramFiles/Android/Projects/OpenCV-android-sdk/sdk/native/jni/include/opencv2/core/mat.inl.hpp:2591: error: undefined reference to 'cv::MatConstIterator::seek(int const*, bool)'
D:/ProgramFiles/Android/Projects/OpenCV-android-sdk/sdk/native/jni/include/opencv2/core/mat.inl.hpp:2591: error: undefined reference to 'cv::MatConstIterator::seek(int const*, bool)'
D:/ProgramFiles/Android/Projects/OpenCV-android-sdk/sdk/native/jni/include/opencv2/core/mat.inl.hpp:2686: error: undefined reference to 'cv::MatConstIterator::seek(long, bool)'
D:/ProgramFiles/Android/Projects/OpenCV-android-sdk/sdk/native/jni/include/opencv2/core/mat.inl.hpp:717: error: undefined reference to 'cv::Mat::copySize(cv::Mat const&)'
D:/ProgramFiles/Android/Projects/OpenCV-android-sdk/sdk/native/jni/include/opencv2/core/mat.inl.hpp:717: error: undefined reference to 'cv::Mat::copySize(cv::Mat const&)'
D:\ProgramFiles\Android\Projects\OpencvTest\app\src\main\jni\src\lib/PAW.cc:167: error: undefined reference to 'cv::remap(cv::_InputArray const&, cv::_OutputArray const&, cv::_InputArray const&, cv::_InputArray const&, int, int, cv::Scalar_<double> const&)'
collect2.exe: error: ld returned 1 exit status**
ninja: build stopped: subcommand failed.
my android.mk
LOCAL_PATH := $(call my-dir)
MY_PATH := $(LOCAL_PATH)
ifeq ($(TARGET_ARCH_ABI),armeabi-v7a)
include $(CLEAR_VARS)
CVROOT := D:/ProgramFiles/Android/Projects/OpenCV-android-sdk/sdk/native/jni
LOCAL_MODULE := FaceTracker
LOCAL_SRC_FILES := libFaceTracker.a #$(wildcard /src/lib/*.cc)
#LOCAL_C_INCLUDES := $(LOCAL_PATH)/include
LOCAL_LDLIBS = -lz -lm
LOCAL_CFLAGS = -Wall -pedantic -g -O3 -ffast-math -funroll-loops -march=armv7-a -mfloat-abi=softfp -mfpu=neon
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
OPENCV_INSTALL_MODULES:=on
include $(CVROOT)/OpenCV.mk
LOCAL_MODULE := opencv_java3
LOCAL_SRC_FILES := native-lib.cpp
LOCAL_C_FLAGS+= -DNDEBUG -Wall -pedantic -g -O3 -ffast-math -funroll-loops -march=armv7-a -mfloat-abi=softfp -mfpu=neon
#LOCAL_C_INCLUDES+= $(NDK_APP_PROJECT_PATH)/stasm4.1.0/stasm
#LOCAL_SRC_FILES += $(NDK_APP_PROJECT_PATH)/libstasm.a
#LOCAL_SRC_FILES += $(wildcard $(NDK_APP_PROJECT_PATH)/stasm/*.cpp)
LOCAL_LDLIBS += -lm -llog -landroid
#LOCAL_SHARED_LIBRARIES += libandroid
LOCAL_STATIC_LIBRARIES += android_native_app_glue
LOCAL_STATIC_LIBRARIES += FaceTracker
LOCAL_ARM_NEON := true
LOCAL_ARM_MODE := arm
include $(BUILD_SHARED_LIBRARY)
$(call import-module,android/native_app_glue)
endif
my build.gradle
import org.apache.tools.ant.taskdefs.condition.Os
def getNdkBuildPath() {
Properties properties = new Properties()
properties.load(project.rootProject.file('local.properties').newDataInputStream())
def command = properties.getProperty('ndk.dir')
if(Os.isFamily(Os.FAMILY_WINDOWS)) {
command +="\\ndk-build.cmd"
} else {
command +="/ndk-build"
}
return command
}
apply plugin: 'com.android.application'
android {
compileSdkVersion 28
defaultConfig {
applicationId "com.example.duru.opencvtest"
minSdkVersion 15
targetSdkVersion 28
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
externalNativeBuild {
cmake {
cppFlags "-frtti -fexceptions"
arguments '-DANDROID_TOOLCHAIN=gcc',
'-DANDROID_STL=gnustl_static'
}
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
externalNativeBuild {
cmake {
path "CMakeLists.txt"
}
}
}
dependencies {
implementation fileTree(include: ['*.jar'], dir: 'libs')
implementation 'com.android.support:appcompat-v7:28.0.0-rc02'
implementation 'com.android.support.constraint:constraint-layout:1.1.3'
testImplementation 'junit:junit:4.12'
androidTestImplementation 'com.android.support.test:runner:1.0.2'
androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
implementation project(':openCVLibrary342')
}
my application.mk
APP_PLATFORM := android-28
APP_ABI := armeabi-v7a
APP_STL := gnustl_static
APP_CPPFLAGS := -frtti -fexceptions -std=c++11
APP_OPTIM := release
and CMakeList.txt
# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html
# Sets the minimum version of CMake required to build the native library.
cmake_minimum_required(VERSION 3.4.1)
set(pathOPENCV D:/ProgramFiles/Android/Projects/OpenCV-android-sdk)
set(pathPROJECT D:/ProgramFiles/Android/Projects/OpencvTest)
set(pathLIBOPENCV_JAVA ${pathPROJECT}/app/src/main/JniLibs/${ANDROID_ABI}/libopencv_java3.so)
set(CMAKE_VERBOSE_MAKEFILE on)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")
include_directories(${pathOPENCV}/sdk/native/jni/include)
# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.
add_library( # Sets the name of the library.
native-lib
# Sets the library as a shared library.
SHARED
# Provides a relative path to your source file(s).
src/main/jni/native-lib.cpp)
add_library( lib_opencv SHARED IMPORTED )
add_library( Tracker SHARED src/main/jni/src/lib/Tracker.cpp )
add_library( PDM SHARED src/main/jni/src/lib/PDM.cc )
add_library( PAW SHARED src/main/jni/src/lib/PAW.cc )
add_library( Patch SHARED src/main/jni/src/lib/Patch.cc )
add_library( IO SHARED src/main/jni/src/lib/IO.cc )
add_library( FDet SHARED src/main/jni/src/lib/FDet.cc )
add_library( FCheck SHARED src/main/jni/src/lib/FCheck.cc )
add_library( CLM SHARED src/main/jni/src/lib/CLM.cc )
set_target_properties(lib_opencv PROPERTIES IMPORTED_LOCATION ${pathLIBOPENCV_JAVA})
# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.
find_library( # Sets the name of the path variable.
log-lib
# Specifies the name of the NDK library that
# you want CMake to locate.
log )
# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.
target_link_libraries( # Specifies the target library.
native-lib
Tracker
PDM
PAW
Patch
IO
FDet
FCheck
CLM
lib_opencv
# Links the target library to the log library
# included in the NDK.
${log-lib} )
opensource are composed of 7 header, 6 .cc files and a .cpp file.

Undefined reference when calling a OpenCL function in Android

I am trying to set a simple project in Android Studio with OpenCL. So I created a new project with NDK support and an empty activity. I have copied the libOpenCL.so from my mobile phone to the folder app\src\main\jniLibs\arm8 and I have downloaded the OpenCL headers from the Khronos webpage and copied them to app\src\main\jni\CL. Furthermore, I have done two modifications to the build.gradle file, I have added a parameter to the cppFlags to include the OpenCL folder and I have set an abi filter to build only for arm8. I copy my build.gradle file here:
apply plugin: 'com.android.application'
android {
compileSdkVersion 26
buildToolsVersion "26.0.1"
defaultConfig {
applicationId "es.um.mompes.testopencl"
minSdkVersion 22
targetSdkVersion 26
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
externalNativeBuild {
cmake {
cppFlags "-std=c++11 -fexceptions -I${projectDir}/src/main/jni"
}
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
externalNativeBuild {
cmake {
path "CMakeLists.txt"
}
}
productFlavors {
arm8 {
ndk {
abiFilter "arm64-v8a"
}
}
}
}
dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support.constraint:constraint-layout:1.0.2'
testCompile 'junit:junit:4.12'
}
I have also added a three lines to the generated native-lib.cpp file to test if OpenCL is working. This is my native-lib.cpp:
#include <jni.h>
#include <string>
#include <CL/cl.h>
extern "C"
JNIEXPORT jstring JNICALL
Java_es_um_mompes_testopencl_MainActivity_stringFromJNI(
JNIEnv *env,
jobject /* this */) {
std::string hello = "Hello from C++";
cl_int err;
// Find the number of OpenCL platforms
cl_uint num_platforms;
err = clGetPlatformIDs(0, NULL, &num_platforms);
return env->NewStringUTF(hello.c_str());
}
However, I must be missing something because I am getting an undefined reference error regarding the OpenCL function when I build the project. This is the complete error:
Execution failed for task ':app:externalNativeBuildArm8Debug'.
Build command failed.
Error while executing process C:\Users\Juan\AppData\Local\Android\Sdk\cmake\3.6.4111459\bin\cmake.exe with arguments {--build C:\Users\Juan\AndroidStudioProjects\TestOpenCL\app.externalNativeBuild\cmake\arm8Debug\arm64-v8a --target native-lib}
[1/1] Linking CXX shared library ........\build\intermediates\cmake\arm8\debug\obj\arm64-v8a\libnative-lib.so
FAILED: cmd.exe /C "cd . && C:\Users\Juan\AppData\Local\Android\sdk\ndk-bundle\toolchains\llvm\prebuilt\windows-x86_64\bin\clang++.exe --target=aarch64-none-linux-android --gcc-toolchain=C:/Users/Juan/AppData/Local/Android/sdk/ndk-bundle/toolchains/aarch64-linux-android-4.9/prebuilt/windows-x86_64 --sysroot=C:/Users/Juan/AppData/Local/Android/sdk/ndk-bundle/sysroot -fPIC -isystem C:/Users/Juan/AppData/Local/Android/sdk/ndk-bundle/sysroot/usr/include/aarch64-linux-android -D__ANDROID_API__=22 -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -Wa,--noexecstack -Wformat -Werror=format-security -std=c++11 -fexceptions -IC:\Users\Juan\AndroidStudioProjects\TestOpenCL\app/src/main/jni -O0 -fno-limit-debug-info -Wl,--exclude-libs,libgcc.a --sysroot C:/Users/Juan/AppData/Local/Android/sdk/ndk-bundle/platforms/android-22/arch-arm64 -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-undefined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -shared -Wl,-soname,libnative-lib.so -o ........\build\intermediates\cmake\arm8\debug\obj\arm64-v8a\libnative-lib.so CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o -llog -lm "C:/Users/Juan/AppData/Local/Android/sdk/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/libs/arm64-v8a/libgnustl_static.a" && cd ."
CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o: In function Java_es_um_mompes_testopencl_MainActivity_stringFromJNI':
C:\Users\Juan\AndroidStudioProjects\TestOpenCL\app\src\main\cpp/native-lib.cpp:14: undefined reference toclGetPlatformIDs'
clang++.exe: error: linker command failed with exit code 1 (use -v to see invocation)
Do you know what am I missing? I've searching for a few hours over the last two days about how to setup OpenCL in Android Studio but everything I find seems to be outdated and doesn't seem to work for my problem.

Look for Android.mk under jni folder. Then add this:
LOCAL_PATH := $(call my-dir) // should already be there
.
.
LOCAL_LDLIBS := $(LOCAL_PATH)/libOpenCL.so
This example takes the libOpenCL.so from the jni root but you can change this for your needs.
Reference: Getting Started with OpenCL on Android

I would recommend you replace the automatic Android Studio NDK building with your own so you have total control.
Then you can use #RonTLV answer to add the library to the Android.mk and have a proper build.
Android Studio by default ignores Android.mk and generates its own with all the .c/.cpp files in the jni folder.
sourceSets {
debug.jniLibs.srcDir 'src/main/obj/local' //debug builds have symbols
release.jniLibs.srcDir 'src/main/libs' //release builds have cleaned libraries
main.jni.srcDirs = [] //disable automatic ndk-build call with auto-generated Android.mk
}
// call regular ndk-build script manually
task ndkBuild(type: Exec) {
if (System.properties['os.name'].toLowerCase(Locale.ROOT).contains('windows')) {
commandLine 'ndk-build.cmd', '-j8', '-C', file('src/main').absolutePath
} else {
commandLine 'ndk-build', '-j8', '-C', file('src/main').absolutePath
}
}
//Make the NDK task depend on Java build Task
tasks.withType(JavaCompile) {
compileTask -> compileTask.dependsOn ndkBuild
}

Link STL library with Gradle CMake project

I have simple Gradle project and trying to add native library building it using CMake
Root CMakeLists.txt
project(mine_lib)
cmake_minimum_required(VERSION 2.8 FATAL_ERROR)
set(CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake")
set(EXECUTABLE_OUTPUT_PATH "${PROJECT_SOURCE_DIR}/bin")
configure_file("${PROJECT_SOURCE_DIR}/src/buildinfo/buildinfo.hpp.in" "${PROJECT_BINARY_DIR}/buildinfo.hpp")
set(CMAKE_VERBOSE_MAKEFILE on)
set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${warnings}")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${warnings}")
add_subdirectory(${PROJECT_SOURCE_DIR}/src)
include_directories(${PROJECT_SOURCE_DIR}/src/data)
include_directories("${PROJECT_BINARY_DIR}")
add_library(mine_lib SHARED "${PROJECT_SOURCE_DIR}/src/jni/jniwrapper.c")
build.gradle
android {
compileSdkVersion 25
buildToolsVersion "25.0.3"
defaultConfig {
applicationId "..."
minSdkVersion 16
targetSdkVersion 25
versionCode 1
versionName "1.0"
defaultConfig {
externalNativeBuild {
cmake {
arguments "-DANDROID_STL=system"
cppFlags "-fexceptions"
}
}
}
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
externalNativeBuild {
cmake {
path "src/main/mine_lib/CMakeLists.txt"
}
}
sourceSets {
main {
jniLibs.srcDirs 'src/main/mine_lib/src/'
}
}
}
In my native library I use part of STL library, for example cstdint. And for now I'm getting compilation error which looks like that:
Error:FAILURE: Build failed with an exception.
* What went wrong:
Execution failed for task ':app:externalNativeBuildDebug'.
> Build command failed.
Error while executing process /AndroidSDK/android-sdk-macosx/cmake/3.6.4111459/bin/cmake with arguments {--build /Users/user/IdeaProjects/Sandbox/MyApp/app/.externalNativeBuild/cmake/debug/mips64 --target mine_lib}
[1/2] Building C object CMakeFiles/mine_lib.dir/src/jni/jniwrapper.c.o
FAILED: /AndroidSDK/android-sdk-macosx/ndk-bundle/toolchains/llvm/prebuilt/darwin-x86_64/bin/clang --target=mips64el-none-linux-android --gcc-toolchain=/AndroidSDK/android-sdk-macosx/ndk-bundle/toolchains/mips64el-linux-android-4.9/prebuilt/darwin-x86_64 --sysroot=/AndroidSDK/android-sdk-macosx/ndk-bundle/sysroot -Dheif_EXPORTS -I/Users/user/IdeaProjects/Sandbox/HEIFGallery/app/src/main/mine_lib/src/reader -I. -isystem /AndroidSDK/android-sdk-macosx/ndk-bundle/sysroot/usr/include/mips64el-linux-android -D__ANDROID_API__=21 -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -fintegrated-as -Wa,--noexecstack -Wformat -Werror=format-security -O0 -fno-limit-debug-info -fPIC -MD -MT CMakeFiles/mine_lib.dir/src/jni/jniwrapper.c.o -MF CMakeFiles/mine_lib.dir/src/jni/jniwrapper.c.o.d -o CMakeFiles/mine_lib.dir/src/jni/jniwrapper.c.o -c /Users/user/IdeaProjects/Sandbox/MyApp/app/src/main/mine_lib/src/jni/jniwrapper.c
In file included from /Users/user/IdeaProjects/Sandbox/MyApp/app/src/main/mine_lib/src/jni/jniwrapper.c:2:
/Users/user/IdeaProjects/Sandbox/MyApp/app/src/main/mine_lib/src/data/dataparser.hpp:16:10: fatal error: 'cstdint' file not found
#include <cstdint>
^~~~~~~~~
1 error generated.
ninja: build stopped: subcommand failed.
* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
BUILD FAILED in 0s
What is the problem really is and how can I solve it?

Based on my understanding the problem could be solved by using a different C++ Library.
Currently you are specifying the following within the build.gradle file:
arguments "-DANDROID_STL=system"
Which, as stated within the following documentation, is:
system: The minimal system C++ runtime library and the default runtime
You'll probably need to change that to another C++ Library but I am not sure which one it would be, could be one of the gnu options. Better yet, it could be solved by removing the statement entirely.

OpenCv with Android studio 2.2+ using new gradle with cmake - undefined reference

I'm having trouble using native OpenCv 3.0.0 with Android Studio 2.2, with new ndk support i.e usin CMAKE build script. Below is the error which i am getting.Am i missing any thing in my gradle or cmake file? Please let me know.
Error:FAILURE: Build failed with an exception.
What went wrong:
Execution failed for task ':app:externalNativeBuildDebug'.
Build command failed.
Error while executing 'C:\Users\User\AppData\Local\Android\sdk\cmake\3.6.3155560\bin\cmake.exe' with arguments {--build E:\OpenCvAndroid\OPecvTry2CSupport\app.externalNativeBuild\cmake\debug\mips64 --target native-lib}
[1/1] Linking CXX shared library ..\obj\mips64\libnative-lib.so
FAILED: cmd.exe /C "cd . && C:\Users\User\AppData\Local\Android\sdk\ndk-bundle\toolchains\llvm\prebuilt\windows-x86_64\bin\clang++.exe -target mips64el-none-linux-android -gcc-toolchain C:/Users/User/AppData/Local/Android/sdk/ndk-bundle/toolchains/mips64el-linux-android-4.9/prebuilt/windows-x86_64 --sysroot=C:/Users/User/AppData/Local/Android/sdk/ndk-bundle/platforms/android-21/arch-mips64 -fPIC -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -Wa,--noexecstack -Wformat -Werror=format-security -fno-exceptions -fno-rtti -O0 -fno-limit-debug-info -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-undefined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -shared -Wl,-soname,libnative-lib.so -o ..\obj\mips64\libnative-lib.so CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o -llog -lm "C:/Users/User/AppData/Local/Android/sdk/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/libs/mips64/libgnustl_static.a" && cd ."
CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o: In function ~Mat':
E:/OpenCVSdk/sdk/native/jni/include\opencv2/core/mat.hpp:278: undefined reference tocv::fastFree(void*)'
CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o: In function cv::Mat::release()':
E:/OpenCVSdk/sdk/native/jni/include\opencv2/core/mat.hpp:367: undefined reference tocv::Mat::deallocate()'
clang++.exe: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.
And my Cmake.txt
cmake_minimum_required(VERSION 3.4.1)
add_library( native-lib
SHARED
src/main/cpp/native-lib.cpp )
include_directories(E\:\\OpenCVSdk\\sdk\\native\\jni\\include )
find_library( log-lib log )
target_link_libraries(native-lib ${log-lib} )
And my Gradle Build file
{ apply plugin: 'com.android.application'
android {
compileSdkVersion 24
buildToolsVersion "24.0.2"
defaultConfig {
applicationId "viki.opecvtry2csupport"
minSdkVersion 16
targetSdkVersion 24
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
externalNativeBuild {
cmake {
cppFlags ""
}
}
}

I fixed my problem by add "lib_opencv" lib to target_link_libraries
target_link_libraries(
native-lib lib_opencv #Just add the lib_opencv
${log-lib} )
don't forget to Link Gradle to your native library
my full CMakeList.txt
cmake_minimum_required(VERSION 3.4.1)
add_library( native-lib
SHARED
src/main/cpp/native-lib.cpp )
find_library( log-lib
log )
target_link_libraries(native-lib lib_opencv
${log-lib} )
set(CMAKE_VERBOSE_MAKEFILE on)
add_library(lib_opencv SHARED IMPORTED)
set_target_properties(lib_opencv PROPERTIES IMPORTED_LOCATION /PROJECT_PATH/openCVLibrary320/src/main/jniLibs/${ANDROID_ABI}/libopencv_java3.so)
include_directories(/OpenCV-android-sdk/sdk/native/jni/include)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")

Setting OpenCV_DIR has worked for me with OpenCV 3.1 and AS 2.2 and the latest Gradle plugin. This is the relevant bit of my CMakeLists.txt.
cmake_minimum_required(VERSION 3.6)
SET(OpenCV_DIR $ENV{HOME}/AndroidDevelopment/opencv-3.1.0/sdk/native/jni)
find_package(OpenCV REQUIRED)
message(STATUS "opencv found: ${OpenCV_LIBS}")
include_directories(${CMAKE_CURRENT_SOURCE_DIR}
${OpenCV_DIR}/include/)
[...]
target_link_libraries(myTarget log ${OpenCV_LIBS} m z android )