apply plugin: 'com.android.application'

android {

    compileSdkVersion

    buildToolsVersion "29.0.2"

    defaultConfig {

        applicationId "com.example.myapplication"

        minSdkVersion

        targetSdkVersion

        versionCode

        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"

        //项目的ndk配置需和使用的库一致,项目的配置在这里设置

        externalNativeBuild {

            cmake {

                cppFlags "-std=c++11"

                //arguments '-DANDROID_STL=c++_static'

                arguments '-DANDROID_STL=c++_shared'

                abiFilters "arm64-v8a"

            }

        }

        //指定jniLibs目录只有这个目录里的.so动态库会被加载到.apk

        sourceSets {

            main {

                jniLibs.srcDirs = ['libs']

            }

        }

    }

    buildTypes {

        release {

            minifyEnabled false

            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'

        }

    }

    externalNativeBuild {

        cmake {

            path "src/main/cpp/CMakeLists.txt"

            version "3.10.2"

        }

    }

}

dependencies {

    implementation fileTree(dir: 'libs', include: ['*.jar'])

    implementation 'androidx.appcompat:appcompat:1.0.2'

    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'

    testImplementation 'junit:junit:4.12'

    androidTestImplementation 'androidx.test:runner:1.1.1'

    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.1'

}

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

cmake_minimum_required(VERSION 3.4.)

#要求支持c++

set(CMAKE_CXX_STANDARD )

set(CMAKE_CXX_STANDARD_REQUIRED ON)

#设置第三方库目录路径参数

set(libs_path ${CMAKE_SOURCE_DIR}/../../../libs)

#引入glog头文件

include_directories( ${libs_path}/include )

##########添加Ceres静态库 begin#########

add_library(

        ceres       #库名字 去掉了 lib 与 .a

        SHARED      #必须的

        IMPORTED    #必须的

)

#指定Ceres静态库位置

set_target_properties(

        ceres

        PROPERTIES IMPORTED_LOCATION

        ${libs_path}/arm64-v8a/libceres.so

)

#引入Ceres的头文件

include_directories( ${libs_path}/include )

##########添加Ceres静态库 end#########

##########添加Eigen库 begin#########

#引入Eigen的头文件

include_directories( ${libs_path}/include )

##########添加Eigen库 begin#########

##########添加添加native-lib动态库 begin#########

add_library(

        native-lib

        SHARED

        native-lib.cpp

)

#查找要链接的android log库

find_library(

        log-lib

        log )

#链接库

target_link_libraries(

        native-lib

        ${log-lib}

        ceres

        #openmap库

        #若编译Ceres时使用了 -DCERES_USE_OPENMP

        #则在使用Ceres时必须链接上OpenMap库

        #omp

)

##########添加添加native-lib动态库 end#########

#include <jni.h>

#include <string>

#include "ceres/ceres.h"

#include "glog/logging.h"

using ceres::AutoDiffCostFunction;

using ceres::CostFunction;

using ceres::Problem;

using ceres::Solver;

using ceres::Solve;

// A templated cost functor that implements the residual r = 10 -

// x. The method operator() is templated so that we can then use an

// automatic differentiation wrapper around it to generate its

// derivatives.

struct CostFunctor {

    template <typename T> bool operator()(const T* const x, T* residual) const {

        residual[] = 10.0 - x[];

        return true;

    }

};

extern "C" JNIEXPORT jstring JNICALL

Java_com_example_myapplication_MainActivity_stringFromJNI(

        JNIEnv* env,

        jobject /* this */) {

    std::string hello = "Hello Ceres";

    // The variable to solve for with its initial value. It will be

    // mutated in place by the solver.

    double x = 0.5;

    const double initial_x = x;

    // Build the problem.

    Problem problem;

    // Set up the only cost function (also known as residual). This uses

    // auto-differentiation to obtain the derivative (jacobian).

    CostFunction* cost_function =

            new AutoDiffCostFunction<CostFunctor, , >(new CostFunctor);

    problem.AddResidualBlock(cost_function, NULL, &x);

    // Run the solver!

    Solver::Options options;

    options.minimizer_progress_to_stdout = true;

    Solver::Summary summary;

    Solve(options, &problem, &summary);

    std::cout << summary.BriefReport() << "\n";

    std::cout << "x : " << initial_x

              << " -> " << x << "\n";

    return env->NewStringUTF(summary.BriefReport().c_str());

}