cmake OpenCV for Android能否利用标准C++支持来获得Android Studio 2.2 for Windows上的原生构建支持?

iyfjxgzm  于 2022-11-11  发布在  Android
关注(0)|答案(4)|浏览(102)

围绕着如何正确构建Android原生OpenCV有很多问题和答案。有些人使用gradle,有些人使用外部工具。这些关于原生OpenCV构建的大量、复杂且经常相互冲突的描述可以通过一个一致的起点来简化;在创建Android Studio 2.2 Beta项目时,可以通过一种方法来包含C支持:第一次
此功能是在2016年6月左右添加的。有关详细信息,请参阅Android tools technical docs
使用Android Studio 2.2或更高版本以及适用于Gradle 2.2.0或更高版本的Android插件,您可以通过将C和C
代码编译到Gradle可与您的APK打包的原生库中,将其添加到您的应用中。然后,您的Java代码可以通过Java原生接口(JNI)调用原生库中的函数。如果您想了解有关使用JNI框架的更多信息,请阅读适用于Android的JNI提示。
检查Include C++ Support会生成一个名为CMakeLists.txt的外部构建文件。


# Sets the minimum version of CMake required to build the native

# library. You should either keep the default value or only pass a

# value of 3.4.0 or lower.

cmake_minimum_required(VERSION 3.4.1)

# 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 it 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).
             # Associated headers in the same location as their source
             # file are automatically included.
             src/main/cpp/native-lib.cpp )

# Searches for a specified prebuilt library and stores the path as a

# variable. Because system libraries are included 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 the

# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
                       native-lib

                       # Links the target library to the log library
                       # included in the NDK.
                       $\{log-lib} )

为了识别使用原生(C++)OpenCV代码的Android项目,项目通常会包含一个*.cpp文件,其中包含JNIEXPORT条目沿着使用#include <opencv...hpp>功能的实现。这与导入OpenCV模块并将libs文件夹复制到jniLibs相反,后者只允许从Java调用OpenCV功能。
是否可以使用此起点来配置OpenCV原生“hello world”应用程序,以证明构建工作正常?

其他信息8月22日

因为这个谜题是关于CMake的,而不是关于OpenCV的,所以我想我应该给予那些对OpenCV不感兴趣的人一个项目起点。
这是一个youtube video,它显示了如何创建一个新的Android Studio项目,导入OpenCV,配置原生C++构建,从而生成与gitHub中的OpenCV“hello world”应用相同的OpenCV应用。

其他信息8月27日

今天提交的版本基于Bruno Alexandre Krinski的回答编译本机OpenCV调用:https://github.com/sengsational/HelloCv。还有一个关于“安装受阻”消息的单独问题,在安装时,Android警告用户“此应用程序包含试图绕过Android安全保护的代码”。由于我不确定这是构建技术的问题,因此我不会扩展此问题以包括该问题(但如果有人对该问题有意见,请告知)。


# Added 2 path definitions to support 20160825 additions

set(pathToProject C:/Users/Owner/AndroidStudioProjects/HelloCv)
set(pathToOpenCv C:/Users/Owner/OpenCV-3.1.0-android-sdk)

# Added by the IDE on project create

cmake_minimum_required(VERSION 3.4.1)

# Two sets suggested by Bruno Alexandre Krinski 20160825

set(CMAKE_VERBOSE_MAKEFILE on)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")

# Addition suggested by Bruno Alexandre Krinski 20160825

include_directories(${pathToOpenCv}/sdk/native/jni/include)

# Added by IDE on project create

add_library( native-lib SHARED src/main/cpp/native-lib.cpp )

# Addition suggested by Bruno Alexandre Krinski 20160825

add_library( lib_opencv SHARED IMPORTED )

# Addition suggested by Bruno Alexandre Krinski 20160825

set_target_properties(lib_opencv PROPERTIES IMPORTED_LOCATION ${pathToProject}/app/src/main/jniLibs/${ANDROID_ABI}/libopencv_java3.so)

# Added by IDE on project create

find_library( log-lib log )

# Added by IDE on project create, Removed and replace with additional parameter suggested by Bruno Alexandre Krinski 20160825

# target_link_libraries( native-lib $\{log-lib} )

target_link_libraries( native-lib $\{log-lib} lib_opencv)
ne5o7dgx

ne5o7dgx1#

看起来您已经导入了opencv模块,现在,打开CMakeList.txt并添加以下行:

set(CMAKE_VERBOSE_MAKEFILE on)

add_library(lib_opencv SHARED IMPORTED)

set_target_properties(lib_opencv PROPERTIES IMPORTED_LOCATION
path-to-your-project/MyApplication/app/src/main/jniLibs/${ANDROID_ABI}/libopencv_java3.so)

include_directories(path-to-opencv-directory/OpenCV-android-sdk/sdk/native/jni/include)

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

并编辑:

target_link_libraries( # Specifies the target library.
                   native-lib
                   lib_opencv
                   # Links the target library to the log library
                   # included in the NDK.
                   $\{log-lib} )

以包含您已建立的lib_opencv。若要完成,请加入下列行:

abiFilters 'x86', 'x86_64', 'armeabi', 'armeabi-v7a', 'arm64-v8a', 'mips', 'mips64'

在您的模块应用程序中,如下所示:

externalNativeBuild {

    cmake {
        cppFlags "-std=c++11 -frtti -fexceptions"
        abiFilters 'x86', 'x86_64', 'armeabi', 'armeabi-v7a', 'arm64-v8a', 'mips', 'mips64'
    }
}

和下面的buildTypes:

sourceSets {
    main {
        jniLibs.srcDirs = ['path to your application /MyApplication/app/src/main/jniLibs/']
    }
}

如需详细信息,请参阅:https://github.com/googlesamples/android-ndk/tree/master/cmake/hello-libs

8xiog9wr

8xiog9wr2#

使用OpenCV 3.2配置实际上可能非常短:

set(OpenCV_STATIC ON)
set(OpenCV_DIR ${OPENCV_HOME}/sdk/native/jni)
find_package (OpenCV REQUIRED)

target_link_libraries(native-lib ${OpenCV_LIBS})

就是这样,4行代码,不需要复制任何东西到你的项目中。只要确保OPENCV_HOME指向OpenCV Android SDK所在的目录。
这种方法的另一个好处是,您可以静态地与OpenCV链接,这将大大减少您的应用程序/库的大小。
我在一个Github项目中使用了这种方法:https://github.com/Fotoapparat/FaceDetector

kmbjn2e3

kmbjn2e33#

按照布鲁诺· Alexandria ·克林斯基的答案做,但是
代替这一行

abiFilters 'x86', 'x86_64', 'armeabi', 'armeabi-v7a', 'arm64-v8a', 'mips', 'mips64'

把这行,(我不知道为什么这对我有用)

abiFilters 'x86', 'x86_64', 'armeabi-v7a', 'arm64-v8a'

(除此之外,请遵循上述答案的所有说明)

ih99xse1

ih99xse14#

Android平台不支持ABI [armeabi]

支持的ABI包括[arm 64-v8 a、armeabi-v7 a、x86、x86_64]。

externalNativeBuild {
            cmake {
              //  cppFlags ""
                cppFlags "-std=c++11 -frtti -fexceptions"
               // abiFilters 'x86', 'x86_64', 'armeabi', 'armeabi-v7a', 'arm64-v8a', 'mips', 'mips64'
                abiFilters 'x86', 'x86_64', 'armeabi-v7a', 'arm64-v8a'
            }
        }

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