Kotlin, NDK and C++ interactions

Question

I\'m not familiar with the Android NDK and I need help to build a Kotlin application using native part of code written in C++. I\'ve found HelloWorld sample using a basic C

Answer 1

Ok, thanks to @Richard, here is my wrapper

ObjectWrapper.kt

Exposes the API I want to use. The keyword external of the method indicates that the body is elsewhere. In my case, in the native layer of the wrapper.

class ObjectWrapper {

    companion object {
        init {
            System.loadLibrary("mylibrary")
        }
    }

    external fun sayHello(name: String): String
}

MyLibrary.cpp

Same API as the kotlin part but the methods are named with the completed package name. Here, I have to the translation between the kotlin world and the native world.

#include <jni.h>
#include <string>
#include "Object.h"

static Object *pObject = NULL;

extern "C" {
    JNIEXPORT jstring Java_com_packagename_ObjectWrapper_sayHello(
            JNIEnv *env,
            jobject /* this */,
            jstring input) {
        pObject = new Object();
        const char *msg = env->GetStringUTFChars(input, JNI_FALSE);
        std::string hello = pObject->getHelloString(msg);
        return env->NewStringUTF(hello.c_str());
    }
}