android使用opencv native方式环境搭建

1.opencv下载：https://opencv.org/releases/ 解压后为OpenCV-android-sdk

2.创建初始Android项目

3.在app/src/main目录下新建jniLibs目录，在app/src/main/cpp目录下新建include目录和src目录

将OpenCV-android-sdk/sdk/native/libs下所有目录复制到jniLibs目录中

将OpenCV-android-sdk/sdk/native/jni/include下的所有目录复制到app/src/main/cpp/include目录中

移动app/src/main/cpp/CMakeLists.txt至app目录下

移动app/src/main/cpp/native-lib.cpp至app/src/main/cpp/src/native-lib.cpp

4.配置文件修改

CMakeLists.txt

# 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 3.4.1)

include_directories(${CMAKE_SOURCE_DIR}/src/main/cpp/include)

#opencv 4.0.1
add_library(libopencv_java4 SHARED IMPORTED)
set_target_properties(libopencv_java4 PROPERTIES IMPORTED_LOCATION
        ${CMAKE_SOURCE_DIR}/src/main/jniLibs/${ANDROID_ABI}/libopencv_java4.so)

#local
add_library(native-lib SHARED src/main/cpp/src/native-lib.cpp)
find_library(log-lib log )

target_link_libraries(native-lib libopencv_java4 ${log-lib} )

app/build.gradle

apply plugin: 'com.android.application'

android {
    compileSdkVersion 29
    buildToolsVersion "29.0.2"
    defaultConfig {
        applicationId "com.wisesoft.wiseface"
        minSdkVersion 21
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags "-std=c++11 -frtti -fexceptions"
                abiFilters 'armeabi-v7a'
                arguments "-DANDROID_STL=c++_shared"
            }
        }
        ndk{
            abiFilters 'armeabi-v7a'
        }
    }
    sourceSets{
        main{
            jniLibs.srcDirs = ['src/main/jniLibs']
            jni.srcDirs = []
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
            ndk{
                abiFilters 'armeabi-v7a'
            }
        }
    }
    externalNativeBuild {
        cmake {
            path "CMakeLists.txt"
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test:runner:1.2.0'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
}

5.刷新配置点击Sync Now并refresh c++

6.使用原生opencv c++ 代码进行开发

#include <jni.h>
#include <string>
#include <opencv2/opencv.hpp>
extern "C" JNIEXPORT jstring JNICALL
Java_com_wisesoft_wiseface_MainActivity_stringFromJNI(
        JNIEnv* env,
        jobject /* this */) {
    std::string hello = "Hello from C++";

    cv::Mat mat;

    return env->NewStringUTF(hello.c_str());
}