Windows编译OpenCV4Android解决undefined reference to std错误

注意OpenCV 4.0.1 解决了这个问题请直接下载OpenCV 4.0.1

但是OpenCV 4.0.1作为模块导入Android Studio会有找不到R.styleable的问题

OpenCV4Android支持三种使用方式

1.Java层调用
2.NDK调用动态库（方便，但是会包含整个.so库）
3.NDK调用静态库（灵活，比如没有用到机器学习模块，libopencv_ml.a里的代码是不会打包到动态库里的）
通过链接静态库的方式使用OpenCV4Android，CMAKE配置如下

#############################prepare for using of opencv static library####################

#first step to use opencv

set(OpenCV_STATIC ON)

#second step to use opencv

set(OpenCV_DIR C:/sdk/opencv-3.4.-android-sdk/sdk/native/jni)

#third step to use opencv

find_package(OpenCV REQUIRED)

###########################################################################################

##################################################the native-lib shared library############

# 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/cpp/native-lib.cpp)

# 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

        #foutth step to use opencv link opencv

        ${OpenCV_LIBS}

        # Links the target library to the log library

        # included in the NDK.

        ${log-lib})

######################################################################################

仅仅是新建项目稍稍修改了native-lib.cpp的代码，在函数里用了下opencv的函数

#include <jni.h>

#include <string>

#include "opencv2/core/core.hpp"

#include "opencv2/imgproc/imgproc_c.h"

extern "C" JNIEXPORT jstring JNICALL

Java_com_example_useprebuiltstaticlibrary_MainActivity_stringFromJNI(

        JNIEnv *env,

        jobject /* this */) {

    std::string hello="hello";

    cv::Mat m=cv::Mat::eye(,,CV_8UC1);

    return env->NewStringUTF(hello.c_str());

}

编译时却报错

Build command failed.

Error while executing process C:\sdk\cmake\3.6.\bin\cmake.exe with arguments {--build C:\sdk\demo\usePrebuiltStaticLibrary\app\.externalNativeBuild\cmake\debug\armeabi-v7a --target native-lib}

[/] Building CXX object CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o

[/] Linking CXX shared library ..\..\..\..\build\intermediates\cmake\debug\obj\armeabi-v7a\libnative-lib.so

FAILED: cmd.exe /C "cd . && C:\sdk\ndk-bundle\toolchains\llvm\prebuilt\windows-x86_64\bin\clang++.exe  --target=armv7-none-linux-androideabi23 --gcc-toolchain=C:/sdk/ndk-bundle/toolchains/arm-linux-androideabi-4.9/prebuilt/windows-x86_64 --sysroot=C:/sdk/ndk-bundle/sysroot -fPIC -isystem C:/sdk/ndk-bundle/sysroot/usr/include/arm-linux-androideabi -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -march=armv7-a -mfloat-abi=softfp -mfpu=vfpv3-d16 -mthumb -mfpu=neon -Wa,--noexecstack -Wformat -Werror=format-security -std=c++11 -std=c++11 -O0 -fno-limit-debug-info  -Wl,--exclude-libs,libgcc.a -Wl,--exclude-libs,libatomic.a -nostdlib++ --sysroot C:/sdk/ndk-bundle/platforms/android-23/arch-arm -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--fix-cortex-a8 -Wl,--exclude-libs,libunwind.a -LC:/sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/armeabi-v7a -Wl,--no-undefined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -shared -Wl,-soname,libnative-lib.so -o ..\..\..\..\build\intermediates\cmake\debug\obj\armeabi-v7a\libnative-lib.so CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o  C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_highgui.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_features2d.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_shape.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_imgcodecs.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_ml.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_videoio.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_dnn.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_flann.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_objdetect.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_core.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_calib3d.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_video.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_superres.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_photo.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_imgproc.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_stitching.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_videostab.a -llog C:/sdk/opencv-3.4.2-android-sdk/sdk/native/3rdparty/libs/armeabi-v7a/liblibprotobuf.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_calib3d.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_features2d.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_highgui.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_videoio.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_imgcodecs.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/3rdparty/libs/armeabi-v7a/liblibjpeg-turbo.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/3rdparty/libs/armeabi-v7a/liblibwebp.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/3rdparty/libs/armeabi-v7a/liblibpng.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/3rdparty/libs/armeabi-v7a/liblibtiff.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/3rdparty/libs/armeabi-v7a/liblibjasper.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/3rdparty/libs/armeabi-v7a/libIlmImf.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_flann.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_video.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_photo.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_imgproc.a C:/sdk/opencv-3.4.2-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_core.a -lz C:/sdk/opencv-3.4.2-android-sdk/sdk/native/3rdparty/libs/armeabi-v7a/libtbb.a -lc C:/sdk/opencv-3.4.2-android-sdk/sdk/native/3rdparty/libs/armeabi-v7a/libcpufeatures.a -ldl -lm -llog C:/sdk/opencv-3.4.2-android-sdk/sdk/native/3rdparty/libs/armeabi-v7a/libtegra_hal.a -latomic -lm "C:/sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/armeabi-v7a/libc++_static.a" "C:/sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/armeabi-v7a/libc++abi.a" "C:/sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/armeabi-v7a/libunwind.a" "-ldl" && cd ."

C:/sdk/opencv-3.4.-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_core.a(system.cpp.o):system.cpp:function std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*) [clone .part.]: error: undefined reference to 'std::basic_ios<char, std::char_traits<char> >::clear(std::_Ios_Iostate)'

C:/sdk/opencv-3.4.-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_core.a(system.cpp.o):system.cpp:function cv::Exception::formatMessage(): error: undefined reference to 'std::basic_stringstream<char, std::char_traits<char>, std::allocator<char> >::basic_stringstream(std::_Ios_Openmode)'

C:/sdk/opencv-3.4.-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_core.a(system.cpp.o):system.cpp:function cv::Exception::formatMessage(): error: undefined reference to 'std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, int)'

C:/sdk/opencv-3.4.-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_core.a(system.cpp.o):system.cpp:function cv::Exception::formatMessage(): error: undefined reference to 'std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, int)'

C:/sdk/opencv-3.4.-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_core.a(system.cpp.o):system.cpp:function cv::Exception::formatMessage(): error: undefined reference to 'std::ostream::put(char)'

C:/sdk/opencv-3.4.-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_core.a(system.cpp.o):system.cpp:function cv::Exception::formatMessage(): error: undefined reference to 'std::ostream::flush()'

C:/sdk/opencv-3.4.-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_core.a(system.cpp.o):system.cpp:function cv::Exception::formatMessage(): error: undefined reference to 'std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, int)'

C:/sdk/opencv-3.4.-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_core.a(system.cpp.o):system.cpp:function cv::Exception::formatMessage(): error: undefined reference to 'std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, int)'

C:/sdk/opencv-3.4.-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_core.a(system.cpp.o):system.cpp:function cv::Exception::formatMessage(): error: undefined reference to 'std::ostream::put(char)'
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C:/sdk/opencv-3.4.-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_core.a(persistence_json.cpp.o):persistence_json.cpp:function icvJSONParseValue(CvFileStorage*, char*, CvFileNode*): error: undefined reference to 'std::string::at(unsigned int)'

C:/sdk/opencv-3.4.-android-sdk/sdk/native/staticlibs/armeabi-v7a/libopencv_core.a(persistence.cpp.o):persistence.cpp:function check_if_write_struct_is_delayed(CvFileStorage*, bool): error: undefined reference to 'std::string::assign(char const*, unsigned int)'

clang++.exe: error: linker command failed with exit code  (use -v to see invocation)

ninja: build stopped: subcommand failed.

google得知是因为编译这些静态库时所用的编译器、标准库等跟NDK当前的版本不同。网上的建议都是stl改为gnustl_static或gnustl_shared之类。可较新的NDK都不支持这些stl了，为了使用OpenCV静态库只能重新编译了。
编译OpenCV4Android的过程里爬了不少坑，总结一下，希望有助于小白们。

1. 安装MinGW
这里不详细的说了，网上很多教程。选择如图三项安装