Android Studio 2.2 链接 opencv 静态库

Question

我正在尝试在 Android Studio 2.2 中链接 opencv 本机库。我发现的所有主题都是使用 Android.mk 文件或 Android Studio 找不到的 build.gradle 文件中的其他方法。

我使用的是 Android Studio 2.2，并通过创建一个支持 c++ 的新项目来创建该项目。

到目前为止，我成功地将 OpenCV 库包含在 c++ 源文件中：

#include <jni.h>
#include <string>
#include "opencv.hpp"

extern "C"
jstring
Java_com_rvstudios_roomscanner_capp_MainActivity_stringFromJNI(
        JNIEnv *env,
        jobject /* this */) {
    std::string hello = "Hello from C++";

    cv::Mat image;
    cv::cvtColor(image, image, CV_BGR2GRAY);

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

当我尝试构建它时，我在 opencv 函数上得到未定义的引用错误，这是因为必须链接静态库（.a 文件）。根据我已经阅读的内容，这应该在 build.gradle 文件中完成。

到目前为止，这是我的 build.gradle 文件：

apply plugin: 'com.android.application'

def targetPlatform = "mips"

android {
    compileSdkVersion 23
    buildToolsVersion "25.0.1"
    defaultConfig {
        applicationId "com.rvstudios.roomscanner.capp"
        minSdkVersion 18
        targetSdkVersion 23
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags ""
                cppFlags.add("-isystem${project.rootDir}/app/src/main/cpp/vision".toString())
            }
        }
    }
    sourceSets.main {
        jni.srcDirs = ["${project.rootDir}/app/src/main/jniLibs/${targetPlatform.toString()}/"]
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
    externalNativeBuild {
        cmake {
            path "CMakeLists.txt"
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:23.4.0'
    compile 'com.android.support:design:23.4.0'
    testCompile 'junit:junit:4.12'
}

我被困在这里，因为我不知道如何链接静态库。我已经看到了大量关于同一问题的 SO 主题，但我阅读的所有内容都使用不同的项目设置，而且我是 Android 开发新手，所以我对此一无所知。

编辑1： 我的 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
             src/main/cpp/vision/opencv.hpp )

# 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}

                        )

Answer 1

在 CMakeLists.txt 中添加：

set(pathToOpenCV /Users/admin/Projects/OpenCV-android-sdk/sdk/native/) // Replace with your OpenCV SDK path
include_directories(${pathToOpenCV}/jni/include)