dnn::net forward in native C++ Android Studio

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Hallo,

I want entwickelt native c++ App in Android studio but I come cross undefined reference to 'cv::dnn.Net::forward(out, layerNames)".

I need help how can I use net.forward(out, layerNames) in native c++.

thanks

hier ist my Code

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

#include <opencv2/imgproc.hpp>
#include <opencv2/highgui.hpp>
#include <opencv2/dnn.hpp>

using namespace std;
using namespace cv;
using namespace cv::dnn;


extern "C" JNIEXPORT jstring JNICALL
Java_com_example_mats86_myapplication_MainActivity_stringFromJNI(
    JNIEnv *env,
    jobject /* this */) {
std::string hello = "Hello from C++";

float confThreshold = 0.5;
float nmsThreshold = 0.4;
int newW = 320;
int newH = 320;
String model = "/storage/emulated/0/DCIM/ImageProcessing/tessdata/frozen_east_text_detection.pb";

string imPath = "/storage/emulated/0/DCIM/ImageProcessing/test.jpg";

Mat im = imread(imPath, IMREAD_COLOR);
Mat orig;
im.copyTo(im);
int origH = im.rows;
int origW = im.cols;

int rW = (int) (origW / float(newW));
int rH = (int) (origH / float(newH));

resize(im, im, Size(newW, newH));
int H = im.rows;
int W = im.cols;

vector<Mat> outs;
vector<String> layerNames(2);
layerNames[0] = "feature_fusion/Conv_7/Sigmoid";
layerNames[1] = "feature_fusion/concat_3";

Net net = readNet(model);

// construct a blob from the image and then perform a forward pass of
// the model to obtain the two output layer sets
Mat frame, blob;
blobFromImage(frame, blob, 1.0, Size(newW, newH), Scalar(123.68, 116.78, 103.94), true, false);
net.setInput(blob);
net.forward(outs, layerNames);

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

error

undefined reference to `cv::dnn::experimental_dnn_34_v7::Net::forward(cv::_OutputArray const&,     std::__ndk1::vector<cv::String, std::__ndk1::allocator<cv::String> > const&)'
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.

hier is my Cmakelist

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

set(CMAKE_VERBOSE_MAKEFILE on)
set(libs "${CMAKE_SOURCE_DIR}/src/main/jniLibs")
include_directories(/Users/mats86/androidTools/opencv-3.4.3-android-sdk/sdk/native/jni/include)

add_library(libopencv_java3 SHARED IMPORTED)
set_target_properties(libopencv_java3 PROPERTIES IMPORTED_LOCATION "${libs}/${ANDROID_ABI}/libopencv_java3.so")

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -frtti -fexceptions")

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)

# 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 ...