如何使用 CMake 在 android 构建中编译和共享两个 C++ 库

Question

我有自定义 C++ 类，我想运行在我的 android 应用程序上。我使用 CMakeLists 成功绑定了我的 C++ 文件。但是由于我的类使用 opencv，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 应用程序中添加 opencv 库，下载了 open cv android sdk 并且厌倦了将其添加到我的项目中。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>

所有来自 c++ 的编译都很好，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.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\ndk0~1.611\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.

Answer 1

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：

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

Answer 2

您的 cmake 项目似乎找不到已安装的 opencv，因此您要么将路径设置为 ${complete_path_to_opencv_installation}/apt，要么将 opencv 安装在 公共安装文件夹

无论哪种方式，您都需要将其传播到您的项目中：如果您将其安装在典型位置（例如 linux 中的 /usr/local/，您需要在 Windows 中设置 export PATH=$PATH:${opencv_installation_path} 或 c:\Path，然后设置路径在环境变量.

通过这样做，find_package(OpenCV) 应该能够找到 opencv 库并设置 OpenCV_INCLUDE_DIRS。 CMakeLists.txt 应该有效：

cmake_minimum_required(VERSION 3)
project( DisplayImage )
find_package( OpenCV REQUIRED )
include_directories( ${OpenCV_INCLUDE_DIRS} )
add_executable( DisplayImage DisplayImage.cpp )
target_link_libraries( DisplayImage ${OpenCV_LIBS} )

或者您也可以在 include_directories 之前 set OpenCV_INCLUDE_DIRS "./app/opencv2" 传播 opencv2/core.hpp.

您也可能对此将 opencv 与 android 结合使用感兴趣。

如何使用 CMake 在 android 构建中编译和共享两个 C++ 库

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