如何将本机库加载到本机android代码中？ （AndroidStudio）

Question

I have a library in C called mylib in the folder jniLibs/your_architecture/mylib.so

In Java, to load the library, you just have to type that code in your source:

static {
  System.loadLibrary("mylib");
}

But how can you load the library in a native C code (in Android Studio) ? I add that the library don't use the JNI conventions, it's a normal shared library.

Answer 1

If this can help someone, here how to load a library in native code c/c++ :

1 - to avoid java.lang.UnsatisfiedLinkError: dlopen failed: add this to the build.gradle into android block :

sourceSets {
    main {
        jniLibs.srcDirs = ['src/main/jniLibs']
    }
}

Assuming that your lib files are in

src/main/jniLibs/{Architecture}/

( depending where is your jniLibs folder, in my case it is located at app/src/main/ but the most time it is in app/ )

---

2 - In your CMakeList, add you library as SHARED and IMPORTED by adding the following block :

add_library(mylib SHARED
            IMPORTED
            )

---

3 - Add target properties to locate you lib mylib.so by adding the following block :

set_target_properties( mylib PROPERTIES 
IMPORTED_LOCATION 
${PROJECT_SOURCE_DIR}/../jniLibs/${ANDROID_ABI}/mylib.so
)

We back forward (/../) here because we concidere that CMakeLists.txt is in

src/main/cpp/

Otherwise, the most time it is in app/ folder, in this case, we don't need to back forward.

So we have to back to main/ before going into jniLibs/

---

4 - Add you lib mylib to your target link libraries :

target_link_libraries(native-library-jni
                      ..
                      ..
                      mylib
                      ..
                      ..
                      )

---

5 - Finally, to call methods of your lib mylib.so , you have to create/copy-past the header containing these methods signatures and include it in your source file : #include "mylib.h"

You can now call your methods [namespace::]method(args...)

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Extra links :

PROJECT_SOURCE_DIR

CMAKE_SOURCE_DIR

Q : Are CMAKE_SOURCE_DIR and PROJECT_SOURCE_DIR the same in CMake?