Native C++ Code in Android Studio with a Static Library - c++

Question

I am trying to make a native C++ code in Android Studio and with CMake. My C++ code uses precompiled static library (.a file).
I included its header .h in my C++ code. I also linked the location of the .h and the .a files in my CMakeList.txt as below:
include_directories(".h file location")
Then:
add_library(lib_fastcv STATIC IMPORTED)
set_target_properties(lib_fastcv PROPERTIES IMPORTED_LOCATION
".a file location")
And at the end:
target_link_libraries (...lib_fastcv....)
However, as soon as I use any function from the .a static library it complains that it cannot recognize the function which means the static library is not linked correctly to my C++ code.
Does anyone know what else I need to do?
Should I also edit my build.gradle to include information about the library file?

Answer 1

this is my solution:
So, first of all, CMake can be weird to use at the beginning.
1- native-lib1 is the output product of CMake. Later java will only see .so of this
add_library( # This is out .so product (libnative-lib1.so)
native-lib1
# Sets the library as a shared library.
SHARED
# These are the input .cpp source files
native-lib.cpp
SRC2.cpp
Any other cpp/c source file you want to compile
)
2- Any library that you included in your souse file, its .h needs to be addressed here:
target_include_directories(# This is out .so product (libnative-lib1.so)
native-lib1 PRIVATE
${CMAKE_SOURCE_DIR}/include)
3- Any actual library you used, its atual .a or .cpp should be addrressed to CMake this way:
target_link_libraries(
# This is out .so product (libnative-lib1.so)
native-lib1
#These are any extra library files that I need for building my source .cpp files to final .so product
${CMAKE_SOURCE_DIR}/lib/libfastcv.a
# Links the target library to the log library
# included in the NDK.
${log-lib})
Then build.gradle it should be mentioned what abi formats we want it to make to make sure you pre built .a files are compatible.
flavorDimensions "version"
productFlavors {
create("arm7") {
ndk.abiFilters("armeabi-v7a")
}
Finally, as a note, the below command did not work to filter abis and above command work, even though they look similar in logic and form to me:
cmake {
cppFlags "-std=c++11"
abiFilters 'armeabi-v7a'
}
}
ndk {
// Specifies the ABI configurations of your native
// libraries Gradle should build and package with your APK.
// This is not working to eliminate
abiFilters 'armeabi-v7a'
}
}