CMake imported library not included in Gradle aar output-CodePudding

In an Android project that loads a C library (mylib.so, which includes a JNI API already), I have a CMakeLists.txt that import the prebuilt library, as per the documentation, like so:

cmake_minimum_required(VERSION 3.10.2)
project(ImportMyLib)

set(MYLIB_PREBUILT_PATH "${CMAKE_CURRENT_SOURCE_DIR}/../../../../src/build/arm64/src")

add_library(mylib SHARED IMPORTED)
set_target_properties(mylib
                      PROPERTIES IMPORTED_LOCATION
                      "${MYLIB_PREBUILT_PATH}/libmylib.so")

I did print ${CMAKE_CURRENT_SOURCE_DIR}/../../../../src/build/arm64/src and checked that ${CMAKE_CURRENT_SOURCE_DIR}/../../../../src/build/arm64/src/libmylib.so does exist.

However, libmylib.so is not included in the resulting .aar, and I don't understand why.

My build.gradle does include the CMakeLists.txt above, like so:

externalNativeBuild {
    cmake {
        path "src/main/cpp/CMakeLists.txt"
    }
}

This is similar to this question, except that it seems there that there was a need to add an IMPORTED target (because of the ExternalProject_Add), whereas here I'm trying to import an already built library.

What am I missing?

CodePudding user response：

You can explicitly request libmylib.so to be included:

externalNativeBuild {
    cmake {
        path "src/main/cpp/CMakeLists.txt"
        targets "mylib" # matches add_library(mylib SHARED IMPORTED)
    }
}

CodePudding user response：

I had missed this part of the documentation:

If you want Gradle to package prebuilt native libraries that are not used in any external native build, add them to the src/main/jniLibs/ABI directory of your module. Versions of the Android Gradle Plugin prior to 4.0 required including CMake IMPORTED targets in your jniLibs directory for them to be included in your app. [...] If you are using Android Gradle Plugin 4.0, move any libraries that are used by IMPORTED CMake targets out of your jniLibs directory to avoid this error.

Moving mylib.so to src/main/jniLibs/ABI does work indeed.