Android Studio: include opencv2 in native-lib.cpp

Question

I am trying to use a native opencv method in AndroidStudio, but I have a problem when I try to include the opencv package in native.lib.cpp.

I already followed different tutorials trying to solve this problem. The most useful was this one. But my problem is that I got an error on the code

 #include <opencv2/core.hpp>

"Cannot find 'opencv2' "

See picture: https://i.stack.imgur.com/6SHxF.png

Following the previous tutorial, that is also described in this thread, I get these files.

app build.gradle

apply plugin: 'com.android.application'

android {
compileSdkVersion 25
buildToolsVersion "25.0.3"
defaultConfig {
    applicationId "esp1718.android.deblur"
    minSdkVersion 16
    targetSdkVersion 25
    versionCode 1
    versionName "1.0"
    testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    externalNativeBuild {
        cmake {
            cppFlags "-std=c++11 -frtti -fexceptions"
            abiFilters 'x86', 'x86_64', 'armeabi-v7a', 'arm64-v8a'
        }
    }
}
buildTypes {
    release {
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
    }
}
sourceSets {
    main {
        jniLibs.srcDirs = ['C:/Users/erikb_000/AndroidStudioProjects/DeBlurGit/app/src/main/jniLibs']
    }
}
externalNativeBuild {
    cmake {
        path "CMakeLists.txt"
    }
}
}

dependencies {
compile fileTree(include: ['*.jar'], dir: 'libs')
androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
    exclude group: 'com.android.support', module: 'support-annotations'
})
compile 'com.android.support:appcompat-v7:25.3.1'
compile 'com.android.support.constraint:constraint-layout:1.0.2'
compile 'com.android.support:design:25.3.1'
testCompile 'junit:junit:4.12'
compile project(':openCVLibrary342')
}

CMakeLists.txt

set(pathToProject C:/Users/erikb_000/AndroidStudioProjects/DeBlurGit)
set(pathToOpenCV C:/Users/erikb_000/Desktop/Erik/Università/EmbeddedSystemsProgramming/Project/OpenCV-android-sdk)

# 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)

set(CMAKE_VERBOSE_MAKEFILE on)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")

include_directories(${pathToOpenCV}/sdk/native/jni/include)

# 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.
         native-lib

         # Sets the library as a shared library.
         SHARED

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

add_library(lib_opencv SHARED IMPORTED)

set_target_properties(lib_opencv PROPERTIES IMPORTED_LOCATION ${pathToProject}/app/src/main/jniLibs/${ANDROID_ABI}/libopencv_java342.so)

# 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.
                   native-lib
                   lib_opencv
                   # Links the target library to the log library
                   # included in the NDK.
                   ${log-lib} )

native-lib.cpp

#include <jni.h>
#include <string>
#include <opencv2/core.hpp>



extern "C" {
JNIEXPORT jstring JNICALL
Java_esp1718_android_deblur_MainActivity_stringFromJNI(
        JNIEnv *env,
        jobject /* this */) {
        std::string hello = "Hello from C++";
    return env->NewStringUTF(hello.c_str());
}

jstring
Java_esp1718_android_deblur_MainActivity_validate(JNIEnv *env, jlong addGray, jlong addrRgba) {
    cv::Rect();
    cv::Mat();
    std::string hello2 = "Hello from validate";
    return env->NewStringUTF(hello2.c_str());
}

}

Note that, unlike the tutorials I found, in the gradle file, in the line abiFilters 'x86', 'x86_64', 'armeabi', 'armeabi-v7a', 'arm64-v8a', 'mips', 'mips64' I had to delete 'armeabi' 'mips' 'mips64' because AndroidStudio gave me some errors saying that they are no longer supported.

I also found a "solution" to this importation problem in another thread, that said to delete these lines from the gradle file

externalNativeBuild {
    cmake {
        path "CMakeLists.txt"
    }
}

It actually solved the #include <opencv2/core.hpp> problem, but generated another one on my mainActivity when I tried to call a native method. So it was not much exaustive. In particular see this picture: https://i.stack.imgur.com/P45um.png

Is there anything wrong in my files? Among the youtube tutorial comments I noticed that other people faced the same problem, and no one found a solution yet.

Android Studio: include opencv2 in native-lib.cpp

0 Answers0