#if __ANDROID__
#include <jni.h>
JNIEXPORT jbyteArray JNICALL
Java_com_my_company_TestClass_process(JNIEnv *env, jobject thiz, jbyteArray command);
#endif
#endif

apply plugin: 'com.android.library'
android {
...
    sourceSets.main {
        jniLibs.srcDir 'src/main/jniLibs'
    }
}

public class TestClass
{
  public native byte[] process(byte[] command);

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