Cannot resolve corresponding JNI function with .so file

Question

I'm completely new to JNI and I have to use an existing compiled .so file. The problem is that Android Studio isn't able to find JNI fuctions. I load my library with a code similiar to this:

public class MyService extends Service{

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

    private native void example();

}

and it gives me an error "Cannot resolve corresponding JNI function Java_com_company_app_MyService_example".

If I run this command (in a terminal)

arm-linux-androideabi-nm -DC mylib.so

I get, between others (I need only few functions of the library),

register_com_company_app_service(_JNIEnv*)

(instead of MyService there is service)

What can I do? Are there problems loading the library or what else?

I tried also to refractor class name "MyService" in "service" but "Java_com_company_app_service_example" wasn't resolved either!

Thanks in advance!

Check my answer how to include `*.so` files in `AndroidStudio`, maybe can helps you, http://stackoverflow.com/a/33164947/3626214 — Aspicas, May 04 '16 at 17:22
It didn't help. If could help, I have only (one) so file and no jar — Mirko, May 04 '16 at 17:36
This sounds like a very strange name for a native method. Are you sure your Java code is correct? — user207421, May 04 '16 at 19:48
Do you see there exported functions that begin with `Java_`? And you should not use `-C` for `nm` command! — Alex Cohn, May 05 '16 at 05:22
Maybe this library expects a separate JNI wrapper library? Or maybe it exports `JNI_OnLoad()`? — Alex Cohn, May 08 '16 at 14:47
Sorry for the late reply but this is a busy period. In the nm output there is a JNI_OnLoad, what does it means? — Mirko, May 14 '16 at 16:32

Yochai Timmer · Answer 1 · 2016-05-08T06:13:04.523

You need to keep in mind that the function signature must match its name in Java, and that it must be exported.
Also, member functions receive the object as a first parameter, and static functions receive the class.

#ifdef __cplusplus
extern "C" {
#endif
 JNIEXPORT void JNICALL Java_Namespace_Class_MemberFunction
        (JNIEnv *, jobject);

 JNIEXPORT void JNICALL Java_Namespace_Class_StaticFunction
        (JNIEnv *, jclass);

#ifdef __cplusplus
}
#endif

So in your case it would be:

 JNIEXPORT void JNICALL Java_com_company_app_MyService_example
        (JNIEnv *, jobject);

Cannot resolve corresponding JNI function with .so file

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