OpenCv with Android studio 2.2+ using a new hail with cmake - undefined

Question

I'm having problems using native OpenCv 3.0.0 with Android Studio 2.2 with new ndk support. I am using a CMAKE build script. Below is the error I am getting. Am I missing something in my gradel or cmake file? Please let me know.

Error: FAILURE: build failed with exception.

• What went wrong: Execution failed for task ': app: externalNativeBuildDebug'.

  Build command failed. An error occurred while executing 'C: \ Users \ User \ AppData \ Local \ Android \ sdk \ cmake \ 3.6.3155560 \ bin \ cmake.exe' with the arguments {--build E: \ OpenCvAndroid \ OPecvTry2CSupport \ app.externalNativeBuild \ cmake \ debug \ mips64 --target native-lib} [1/1] Linking the 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 / platform / android- 21 / arch-mips64 -fPIC -g -DANDROID -Functions -funwind-tables -fstack-protector-strong -no- canonical-prefixes -Wa, - noexecstack -Wformat -Werror = format-security -fno-exceptions -fno-rtti -O0 -fno-limit-debug-info -Wl, -bui ld-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 / LIES / MIPS64 / libgnustl_stati ca" & & CD. " CMakeFiles / native-lib.dir / src / main / cpp / native-lib.cpp.o: In ~Mat': E:/OpenCVSdk/sdk/native/jni/include\opencv2/core/mat.hpp:278: undefined reference to function ~Mat': E:/OpenCVSdk/sdk/native/jni/include\opencv2/core/mat.hpp:278: undefined reference to cv :: fastFree (void *) 'CMakeFiles / native-lib.dir / src / main / cpp / native-lib.cpp.o: In the cv::Mat::release()': E:/OpenCVSdk/sdk/native/jni/include\opencv2/core/mat.hpp:367: undefined reference to function cv::Mat::release()': E:/OpenCVSdk/sdk/native/jni/include\opencv2/core/mat.hpp:367: undefined reference to cv :: Mat :: deallocate () 'clang ++. exe: error: the linker command failed with exit code 1 (use -v to see the call) ninja: build stopped: the 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 Gradel 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 "" } } } 

Answer 1

I fixed my problem by adding lib_opencv lib to target_link_libraries

 target_link_libraries( native-lib lib_opencv #Just add the lib_opencv ${log-lib} ) 

don't forget the gradle link 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") 

Answer 2

Setting up OpenCV_DIR worked for me with OpenCV 3.1 and AS 2.2 and the latest Gradle plugin. This is the corresponding 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} mz android )