app\src\main\cpp\CMakeLists.txt : C/C++ debug|arm64-v8a : Configuration failed

Question

I copied the necessary .so files under the jnilibs folder, and configured the below files in an android ndk project using jni interface. While running the project, it throws an error as seen below.

build.gradle

defaultConfig{
        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags "-frtti -fexceptions"
                abiFilters 'arm64-v8a'
            }
        }
    }

    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"
        }
    }

This my CMakeLists.txt

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html
cmake_minimum_required(VERSION 3.4.1)
# Sets the minimum version of CMake required to build the native library.
#Import header file
include_directories(src/main/jniLibs/include)

#Declare the import file to change the directory variable ARM_DIR, which uses the relative directory with the system, because using the relative path does not seem to work
set(ARM_DIR C:/Users/Username/AndroidStudioProjectsFolder/ExamplAppName/app/src/main/jniLibs)

#Add an example of so library.
add_library(avdevice
        SHARED
        IMPORTED)
set_target_properties(avdevice
        PROPERTIES IMPORTED_LOCATION
        ${ARM_DIR}/arm64-v8a/libavdevice.so)

#Adding other so libraries in the same format as above
#Link library
target_link_libraries(
        native-lib
        avdevice
        avformat
        ${log-lib} )

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

Its native-lib.cpp file under the cpp/ directory:

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

extern "C"
{
#include "libavformat/avformat.h"
}

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

.java source code:

static {
            System.loadLibrary("avdevice");
            System.loadLibrary("avformat");
            System.loadLibrary("native-lib");
        }

    TextView tv = findViewById(R.id.sample_text);
    tv.setText(stringFromJNI());

Error:

**Starting Gradle Daemon...
Gradle Daemon started in 4 s 270 ms
KotlinDslScriptsParameter(correlationId=22803889351800, scriptFiles=[]) => StandardKotlinDslScriptsModel(scripts=[], commonModel=CommonKotlinDslScriptModel(classPath=[], sourcePath=[], implicitImports=[]), dehydratedScriptModels={}) - took 0.128 secs

app\src\main\cpp\CMakeLists.txt : C/C++ debug|arm64-v8a : Configuration failed.
app\src\main\cpp\CMakeLists.txt : C/C++ debug|arm64-v8a : CMake Error at app\src\main\cpp\CMakeLists.txt:21 (target_link_libraries):
  Cannot specify link libraries for target "native-lib" which is not built by
  this project

app\src\main\cpp\CMakeLists.txt : C/C++ debug|arm64-v8a : Configuration failed.
executing external native build for cmake 
app\src\main\cpp\CMakeLists.txt

CONFIGURE SUCCESSFUL in 3m 33s**

Answer 1

The apparent issue here concerns the line in CMake file:

target_link_libraries(
        native-lib
        avdevice
        avformat
        ${log-lib} )

It references libraries (the native-lib target and ${log-lib} library variable) before they have even been defined. This will certainly cause CMake to issue an error. You should uncomment the remainder of your CMake file, and link your imported library targets to native-lib in the existing target_link_libraries() call:

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).
             native-lib.cpp )

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 )

target_link_libraries( # Specifies the target library.
                       native-lib
                       # Link your imported library targets here also.
                       avdevice
                       avformat
                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib} )