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c++ - 如何使用 CMake 在 android 构建上编译和共享两个 c++ 库

问题描述

我有想要在我的 android 应用程序上运行的自定义 C++ 类。我成功地使用 . 绑定了我的 C++ 文件CMakeLists。但是当我的课程使用opencv时，我遇到了一个很明显的问题

fatal error: 'opencv2/core.hpp' file not found

然后我尝试在我的 android 应用程序上添加 opencv 库，下载了 open cv android sdk 并厌倦了将它添加到我的项目中。下面是文件夹结构

android 
   -> app
       -> opencv2
          All the opencv2 c++ files and folders
       ->folder1
          My custom c++ classes which will import opencv2.

以下是我的 CMakeLists.txt 文件

cmake_minimum_required(VERSION 3.4.1)  # for example

set(CMAKE_TRY_COMPILE_TARGET_TYPE "STATIC_LIBRARY")

PROJECT(tag)


set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")

 add_library( tag_native
              # Sets the library as a shared library.
              SHARED
              # Provides a relative path to your source file(s).
              "./folder1/tag_native.cpp" )


add_library( opencv2
             # Sets the library as a shared library.
             SHARED
             # Provides a relative path to your source file(s).
             "./opencv2/" )

set_target_properties(opencv2 PROPERTIES LINKER_LANGUAGE CXX)

这是我的 cpp 文件的示例

#include <stdint.h>
#include <string.h>
#include <stdio.h>
#include <vector>
#include <iostream>
#include <opencv2/core.hpp>

c++ 中的所有内容都编译得很好，但我仍然遇到同样的问题

* What went wrong:
Execution failed for task ':app:externalNativeBuildDebug'.
> Build command failed.
  Error while executing process C:\Users\Brainants with arguments {Technology\AppData\Local\Android\Sdk\cmake\3.10.2.4988404\bin\ninja.exe -C E:\Squtag\Squtag Mobile\android\app\.cxx\cmake\debug\armeabi-v7a opencv2 squtag_native}
  ninja: Entering directory `E:\Squtag\Squtag Mobile\android\app\.cxx\cmake\debug\armeabi-v7a'
  [1/2] Building CXX object CMakeFiles/squtag_native.dir/E_/Squtag/Squtag_Mobile/ios/Runner/Squtag_Native/squtag_native.cpp.o
  FAILED: CMakeFiles/squtag_native.dir/E_/Squtag/Squtag_Mobile/ios/Runner/Squtag_Native/squtag_native.cpp.o 
  C:\Users\BRAINA~1\AppData\Local\Android\Sdk\ndk\210~1.611\TOOLCH~1\llvm\prebuilt\WINDOW~1\bin\CLANG_~1.EXE --target=armv7-none-linux-androideabi24 --gcc-toolchain="C:/Users/Brainants Technology/AppData/Local/Android/Sdk/ndk/21.0.6113669/toolchains/llvm/prebuilt/windows-x86_64" --sysroot="C:/Users/Brainants Technology/AppData/Local/Android/Sdk/ndk/21.0.6113669/toolchains/llvm/prebuilt/windows-x86_64/sysroot"  -Dsqutag_native_EXPORTS  -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -march=armv7-a -Wformat -Werror=format-security  -fsanitize=address -fno-omit-frame-pointer -std=c++11 -O0 -fno-limit-debug-info  -fPIC -MD -MT CMakeFiles/squtag_native.dir/E_/Squtag/Squtag_Mobile/ios/Runner/Squtag_Native/squtag_native.cpp.o -MF CMakeFiles\squtag_native.dir\E_\Squtag\Squtag_Mobile\ios\Runner\Squtag_Native\squtag_native.cpp.o.d -o CMakeFiles/squtag_native.dir/E_/Squtag/Squtag_Mobile/ios/Runner/Squtag_Native/squtag_native.cpp.o -c "E:/Squtag/Squtag Mobile/ios/Runner/Squtag Native/squtag_native.cpp"
  E:/Squtag/Squtag Mobile/ios/Runner/Squtag Native/squtag_native.cpp:6:10: fatal error: 'opencv2/core.hpp' file not found
  #include <opencv2/core.hpp>
           ^~~~~~~~~~~~~~~~~~
  1 error generated.
  ninja: build stopped: subcommand failed.

标签： c++opencvcmakeandroid-ndk

解决方案

你得到的错误是告诉你它找不到opencv包含文件：

#include <opencv2/core.hpp>

您需要找到 opencv2 文件夹，并将其作为附加包含目录传递给 cmake：

https://cmake.org/cmake/help/v3.0/command/include_directories.html

示例：在 Android Studio 上通过 CMake 将 OpenCV 添加到 Native C 代码中

cmake_minimum_required(VERSION 3.4.1)
set(OpenCV_DIR "src/sdk/native/jni")
find_package(OpenCV REQUIRED)
message(STATUS "OpenCV libraries: ${OpenCV_LIBS}")
include_directories(${OpenCV_INCLUDE_DIRS})

或者您可以使用这种方法： https ://github.com/ahasbini/Android-OpenCV/blob/master/app/CMakeLists.txt

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