JNI C++ Callbacks

Question

I have a c++ function which accepts a lambda as a parameter. This function calls a piece of java code.

I was wondering how would I get the java code to call the lambda once it's done, in effect calling back to the C++ code.

Answer 1

JavaCPP does that. For example, the following code in C++:

#include "jniFoo.h"

int main() {
    JavaCPP_init(0, NULL);
    foo(6, 7);
}

With this Java class:

import com.googlecode.javacpp.*;
import com.googlecode.javacpp.annotation.*;

public class Foo {
    public static class Callback extends FunctionPointer {   
        public @Name("foo") void call(int a, int b) { 
            System.out.println("bar " + a * b);
        }
    }
}

Produces the following output:

bar 42