13、使用Android Studio开发工具，将一个QT含有第三方库的工程打包成一个动态so供Android Studio开发人员调用

 基本思想：想把一个使用QT开发的工程，（其中实现逻辑涉及FFMPEG NCNN OPENCV的工程）打包成一个动态库，供Android小组调用

 一、 构建一个简单的clion工程，该工程中调用了第三方的opencv，完成了一个像素点的累加;

cmakelists.txt

cmake_minimum_required(VERSION 3.21)
project(untitled1)
find_package(OpenCV REQUIRED)
set(CMAKE_CXX_STANDARD 14)

add_executable(untitled1 main.cpp cv_item.cpp cv_item.h)
target_link_libraries(untitled1 ${OpenCV_LIBS} )

main.cpp

#include "cv_item.h"
cvItem *cvObject= nullptr;
int main() {
     cvObject=new cvItem();
    cvObject->init(4,4,12,12);
    cv::Mat img(600, 600, CV_8UC3, cv::Scalar(255, 255, 255));
    int a= cvObject->process(img);
    printf("a=%d\n",a);
    return 0;
}

cv_item.h

//
// Created by ubuntu on 2022/2/24.

#ifndef UNTITLED1_CV_ITEM_H
#define UNTITLED1_CV_ITEM_H
#include <iostream>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
using namespace std;
using namespace cv;

class cvItem {
public:
    cvItem();
    ~cvItem();
public:
    void init(int x,int y,int width,int height);
    int process(cv::Mat img);

private:
    int x,y,width,height;
};

#endif //UNTITLED1_CV_ITEM_H

cv_item.cpp

//
// Created by ubuntu on 2022/2/24.
//
#include "cv_item.h"
cvItem::cvItem(){
    x=0;
    y=0;
    width=1;
    height=1;
}
cvItem::~cvItem(){

}
void cvItem::init(int x,int y,int width,int height) {
    this->x=x;
    this->y=y;
    this->width=width;
    this->height=height;
}

int cvItem::process(cv::Mat img) {

    cvtColor(img, img, cv::COLOR_BGR2GRAY);//使图片灰度化
     int sum=0;
    //使用二维数组循环读取 row代表行 col是列
    for (int row = 0; row < img.rows; row++)//行循环
    {
        for (int col = 0; col < img.cols; col++)//列循环
        {
          sum+= img.at<uchar>(row, col);
        }
    }
    
    return sum;
}

测试结果

/home/ubuntu/CLionProjects/untitled1/cmake-build-debug/untitled1
a=91800000

Process finished with exit code 0

二、创建一个JNI工程，导入一下nihui大师的opencv-mobile库，修改一下androids studio 的文件

（1）、整个文件的目录结构，最好把JNI的接口单独写一个package，这很重要，不仅JNI的返回函数名字含有这个包的层次名，而且一旦需要从JNI返回list数据到java段，也需要该层次包名

（2）、同时为了后面生成的动态库做准备，设置一下生成的库类型

  (3)、native-lib.cpp文件内容

#include <jni.h>
#include <string>

#include "cv_item.h"
cvItem *cvObject= nullptr;
extern "C" JNIEXPORT jstring JNICALL
Java_com_sxj731533730_test_Test_stringFromJNI(
        JNIEnv* env,
        jobject /* this */) {

    cvObject=new cvItem();
       cvObject->init(4,4,12,12);
       cv::Mat img(600, 600, CV_8UC3, cv::Scalar(255, 255, 255));
      int a= cvObject->process(img);
    std::string str ="a="+ to_string(a);
    return env->NewStringUTF(str.c_str());
}

cmakelists.txt文件内容，生成动态库

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html

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

cmake_minimum_required(VERSION 3.18.1)

# Declares and names the project.

project("myapplication")

# 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 them for you.
# Gradle automatically packages shared libraries with your APK.
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fopenmp")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fopenmp")
if(DEFINED ANDROID_NDK_MAJOR AND ${ANDROID_NDK_MAJOR} GREATER 20)
    set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -static-openmp")
endif()
set(OpenCV_DIR ${CMAKE_SOURCE_DIR}/opencv-mobile-4.5.4-android/sdk/native/jni)
find_package(OpenCV REQUIRED core imgproc)

include_directories(${CMAKE_SOURCE_DIR}/include)

add_library( # Sets the name of the library.
        myapplication

        # Sets the library as a shared library.
        SHARED

        # Provides a relative path to your source file(s).
        native-lib.cpp
        cv_item.cpp
        )

# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries 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 this
# build script, prebuilt third-party libraries, or system libraries.

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

测试结果，也同时生成了我们需要的库文件，上述cmakelists.txt文件，

 （4）、生成的库在这个目录，拷贝出来，新创建一个工程测试一下，保证包名一致即可，我直接在原工程上，删文件了构造新工程了

 （5）、在原代码基础上，删掉cv_item.cpp文件，将上述的so文件导入main/jniLIbs/libs/目录下,在build.gradle添加导入so，

    sourceSets{
        main{
            jniLibs.srcDirs=["src/main/jniLibs/libs"]
            jniLibs.srcDirs=["libs"]
        }
    }

同时在cmakelists.txt导入配置so动态库，删掉原来引用的cv_item.cpp

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html

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

cmake_minimum_required(VERSION 3.18.1)

# Declares and names the project.

project("myapplication")
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fopenmp")
set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fopenmp")
if(DEFINED ANDROID_NDK_MAJOR AND ${ANDROID_NDK_MAJOR} GREATER 20)
    set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -static-openmp")
endif()
set(OpenCV_DIR ${CMAKE_SOURCE_DIR}/opencv-mobile-4.5.4-android/sdk/native/jni)
find_package(OpenCV REQUIRED core imgproc)

include_directories(${CMAKE_SOURCE_DIR}/include)


add_library(libmyapplication SHARED IMPORTED)
set_target_properties(libmyapplication PROPERTIES IMPORTED_LOCATION ${CMAKE_SOURCE_DIR}/../jniLibs/libs/${ANDROID_ABI}/libmyapplication.so)


# 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 them for you.
# Gradle automatically packages shared libraries with your APK.

add_library( # Sets the name of the library.
        myapplication

        # Sets the library as a shared library.
        SHARED

        # Provides a relative path to your source file(s).
        native-lib.cpp)

# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries 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 this
# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
        myapplication
        ${OpenCV_LIBS}
        libmyapplication
        # Links the target library to the log library
        # included in the NDK.
        ${log-lib})

测试一下可用

这是原工程的目录架构 

新工程的目录架构，要保证system.loadLibrary的库引入名字是动态库的名字，同时在com下构建的目录结构和原文件结构一致 com/sxj731533730/test/test,

同时别忘修改cmakelists.txt引入动态包和修改build.gradle包含lib库

build.gradle

sourceSets{
        main{
            jniLibs.srcDirs=["src/main/jniLibs/libs"]
            jniLibs.srcDirs=["libs"]
        }
    }

测试结果

 通过上述方法，本菜鸡将一个QT工程中含有FFMPEG和NCNN、OPENCV的三方实现工程编译成了so，可以方便调用了，当然需要你一开始有交叉编译好的FFMPEG NCNN OPENCV的android包支持