适用于 Android 的 OpenCV 能否利用标准 C++ 支持在适用于 Windows 的 Android Studio 2.2 上获得本机构建支持? [英] Can OpenCV for Android leverage the standard C++ Support to get native build support on Android Studio 2.2 for Windows?

问题描述

围绕正确获取用于 android 构建的本机 opencv 有很多问题和答案.有些使用 gradle，有些使用外部工具.这些对原生 OpenCV 构建的众多、复杂且经常相互冲突的描述可以通过一致的起点进行简化；创建 Android Studio 2.2 Beta 项目时，有一种方法可以包含 C++ 支持:

There are many questions and answers surrounding getting native opencv for android building properly. Some use gradle, others use external tools. These numerous, complicated, and often conflicting descriptions for native OpenCV builds might be simplified with a consistent starting point; when creating an Android Studio 2.2 Beta project, there is an way to include C++ support:

此功能于 2016 年 6 月左右添加.请参阅 Android 工具技术文档 了解更多信息.

This feature was added around June of 2016. See Android tools technical docs for more information.

将 Android Studio 2.2 或更高版本与适用于 Gradle 2.2.0 或更高版本的 Android 插件一起使用，您可以通过将 C 和 C++ 代码编译到 Gradle 可以与您的 APK 打包在一起的本机库中来将 C 和 C++ 代码添加到您的应用中.然后，您的 Java 代码可以通过 Java 本机接口 (JNI) 调用本机库中的函数.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 技巧.

Using Android Studio 2.2 or higher with the Android plugin for Gradle version 2.2.0 or higher, you can add C and C++ code to your app by compiling it into a native library that Gradle can package with your APK. Your Java code can then call functions in your native library through the Java Native Interface (JNI). If you want to learn more about using the JNI framework, read JNI tips for Android.

检查 Include C++ Support 会生成一个名为 CMakeLists.txt 的外部构建文件.

Checking the Include C++ Support generates an external build file called CMakeLists.txt.

# 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} )

要识别使用原生 (C++) OpenCV 代码的 Android 项目，该项目通常会包含一个 *.cpp 文件，其中包含 JNIEXPORT 条目以及使用 <代码>#include 功能.这与导入 OpenCV 模块并将 libs 文件夹复制到 jniLibs 不同，后者只允许从 Java 调用 OpenCV 功能.

To recognize an Android project that uses native (C++) OpenCV code, the project will typically include a *.cpp file containing JNIEXPORT entries along with implementations that use #include <opencv...hpp> functionality. This, as opposed to importing the OpenCV module and copying the libs folder into jniLibs, which only allows calling OpenCV functionality from Java.

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?

Is it possible to use this starting point to configure a OpenCV native 'hello world' app, proving the build is working?

附加信息 8/22
由于这个谜题是关于 CMake 而不是关于 OpenCV，我想我会为那些对 OpenCV 不感兴趣的人提供一个项目起点.使用 Android Studio 中的 OpenCV 中的信息，您可以合理快速地启动起点项目.

ADDITIONAL INFORMATION 8/22
Since this puzzle is about CMake and less about OpenCV, I thought I'd give out a project starting point for those not interested in OpenCV. You could get the starting point project going reasonably quickly using the information in OpenCV in Android Studio.

这是一个 youtube 视频，展示了创作一个新的 Android Studio 项目，导入 OpenCV，配置本机 C++ 构建，从而产生与 gitHub 中的应用程序相同的 OpenCVhello world"应用程序.

Here is a youtube video that shows the creation of a new Android Studio project, importing OpenCV, configuring the native C++ build, resulting in the OpenCV "hello world" application that's equal to the one in gitHub.

附加信息 8/27
今天提交的版本，基于 Bruno Alexandre Krinski 确实编译原生 OpenCV 调用的回答:https://github.com/sengsational/HelloCv .有一个关于安装被阻止"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含该问题(但如果有人对此问题有意见，请提供建议).

ADDITIONAL INFORMATION 8/27
The version committed today, based on the answer from Bruno Alexandre Krinski does compile native OpenCV calls: https://github.com/sengsational/HelloCv . There is a separate problem concerning the "Installation Blocked" message, where, upon installation, Android warns the user "This app contains code that attempts to bypass Android's security protections." Since I am unsure that this is an issue with the build technique, I will not expand this question to include that issue (but if someone has input on that problem, please advise).

#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)

推荐答案

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

It seems you already have imported the opencv module, now, open your CMakeList.txt and add the follow lines:

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

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} )

包含您创建的 lib_opencv.最后，添加以下行:

to include your lib_opencv that you have created. To finish, you add the follow line:

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

在你的模块应用中，像这样:

in your module app, like this:

externalNativeBuild {

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

及以下您添加的 buildType:

and below of buildTypes you add:

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

更多详情，你可以看这个:https://github.com/googlesamples/android-ndk/tree/master/cmake/hello-libs

For more details, you can see this: https://github.com/googlesamples/android-ndk/tree/master/cmake/hello-libs

这篇关于适用于 Android 的 OpenCV 能否利用标准 C++ 支持在适用于 Windows 的 Android Studio 2.2 上获得本机构建支持?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！