android - OpenCV - NDK 更新后对 'cv::CascadeClassifier::detectMultiScale()' 的 undefined reference

Question

昨天我将我的 Android Studio 包含的 NDK 更新到版本 17.0.4754217从那时起我就不能再运行我的应用程序了。当我尝试在更新后重新运行代码时，它给了我错误 ABIs [mips64, armeabi, mips] are not supported for platform. Supported ABIs are [armeabi-v7a, arm64-v8a, x86, x86_64]所以我在我的 app.gradle 中将它们排除在项目之外按以下方式归档:abiFilters 'x86', 'x86_64', /*'armeabi',*/ 'armeabi-v7a', 'arm64-v8a'/*, 'mips', 'mips64'*/ .

但是，从那时起，我在使用 OpenCV 函数的 C++ 文件中遇到了问题 cv::CascadeClassifier::detectMultiScale .

它总是显示错误:CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o: In function detectAndDisplay(cv::Mat, double, int, std::__ndk1::basic_string<char, std::__ndk1::char_traits<char>, std::__ndk1::allocator<char> >, cv::CascadeClassifier&)':
D:\Schule\OpenCV\ARcpp\app\src\main\cpp/native-lib.cpp:158: undefined reference to cv::CascadeClassifier::detectMultiScale(cv::_InputArray const&, std::__ndk1::vector<cv::Rect_<int>, std::__ndk1::allocator<cv::Rect_<int> > >&, double, int, int, cv::Size_<int>, cv::Size_<int>)'.

我这样调用函数:cascadeClassifier.detectMultiScale(frame_gray, sights, scaleFactor, minNeighbours, 0 | CV_HAAR_SCALE_IMAGE, Size(30, 30)); .其余代码与 OpenCV 教程中显示的非常相似 https://docs.opencv.org/2.4/doc/tutorials/objdetect/cascade_classifier/cascade_classifier.html .

除了 NDK，我还使用 CMake 和 LLDB，我包含的 OpenCV 库是 openCVLibrary320 .同样，所有这些都有效，直到我下载了提到的 NDK 更新。

在构建或执行应用程序时始终出现的其余错误是:Build command failed.
Error while executing process C:\Users\chris\AppData\Local\Android\Sdk\cmake\3.6.4111459\bin\cmake.exe with arguments {--build D:\Schule\OpenCV\ARcpp\app\.externalNativeBuild\cmake\debug\arm64-v8a --target native-lib}
[1/1] Linking CXX shared library ..\..\..\..\build\intermediates\cmake\debug\obj\arm64-v8a\libnative-lib.so
FAILED: cmd.exe /C "cd . && C:\Users\chris\AppData\Local\Android\Sdk\ndk-bundle\toolchains\llvm\prebuilt\windows-x86_64\bin\clang++.exe --target=aarch64-none-linux-android --gcc-toolchain=C:/Users/chris/AppData/Local/Android/Sdk/ndk-bundle/toolchains/aarch64-linux-android-4.9/prebuilt/windows-x86_64 --sysroot=C:/Users/chris/AppData/Local/Android/Sdk/ndk-bundle/sysroot -fPIC -isystem C:/Users/chris/AppData/Local/Android/Sdk/ndk-bundle/sysroot/usr/include/aarch64-linux-android -D__ANDROID_API__=21 -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -Wa,--noexecstack -Wformat -Werror=format-security -std=c++11 -std=c++11 -frtti -fexceptions -O0 -fno-limit-debug-info -Wl,--exclude-libs,libgcc.a -Wl,--exclude-libs,libatomic.a -nostdlib++ --sysroot C:/Users/chris/AppData/Local/Android/Sdk/ndk-bundle/platforms/android-21/arch-arm64 -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -LC:/Users/chris/AppData/Local/Android/Sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/arm64-v8a -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\arm64-v8a\libnative-lib.so CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o -llog ../../../../src/main/jniLibs/arm64-v8a/libopencv_java3.so -latomic -lm "C:/Users/chris/AppData/Local/Android/Sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/arm64-v8a/libc++_static.a" "C:/Users/chris/AppData/Local/Android/Sdk/ndk-bundle/sources/cxx-stl/llvm-libc++/libs/arm64-v8a/libc++abi.a" && cd ."
clang++.exe: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.

我真的迷路了，希望有人知道答案。

Answer 1

OpenCV 是用 ANDROID_STL=gnustl_static 构建的.升级后，您的 NDK 将改用默认的 libc++。您可以在 app/build.gradle 中明确设置 ANDROID_STL:

android { defaultConfig { externalNativeBuild { cmake {
    arguments '-DANDROID_STL=gnustl_static'
} } } }

(参见示例 here)。