如何使用JNA回调 [英] How to use JNA callback

问题描述

我使用JNA来调用dll文件的函数。

I am using JNA to call functions of a dll file.

simpleDLL.h：

simpleDLL.h:

typedef int (__stdcall *eventCallback)(unsigned int id, int value);

namespace test
{
   class hotas
   {
   public:
   static __declspec(dllexport) int readValue(int a);
   static __declspec(dllexport) void setCallback(eventCallback evnHnd);
   };
}

simpleDLL.cpp：

simpleDLL.cpp:

#include "simpleDLL.h"
#include <stdexcept>
using namespace std;

namespace test
{
    eventCallback callback1 = NULL;
int test::readValue(int a)
{
    return 2*a;
}

void test::setCallback(eventCallback evnHnd)
{
    callback1 = evnHnd;
}  
}

我的Java接口看起来像这样：

My Java Interface looks like this:

public interface DLLMapping extends Library{

DLLMapping INSTANCE = (DLLMapping) Native.loadLibrary("simpleDLL", DLLMapping.class);

int readValue(int a);

public interface eventCallback extends Callback {

    boolean callback(int id, int value);
}

public void setCallback(eventCallback evnHnd);
}

最后是java main：

And finally the java main:

public static void main(String[] args) {

    DLLMapping sdll = DLLMapping.INSTANCE;

    int a = 3;
    int result = sdll.readValue(a);
    System.out.println("Result: " + result);

    sdll.setCallback(new eventCallback(){
        public boolean callback(int id, int value) {
            //System.out.println("bla");
            return true;
        }
    });
}

我的问题是我得到错误，java找不到函数setCallback 。
我的代码有什么问题？

My problem is that I got the error, that java cannot find the function setCallback. What's wrong on my code?

感谢您的帮助！

推荐答案

C ++与C不一样。从DLL中删除符号（http://dependencywalker.com），你会看到函数名（至少从链接器的角度来看）是不要setCallback。

C++ is not the same thing as C. Dump the symbols from your DLL (http://dependencywalker.com), and you will see that the function name (at least from the linker's point of view) is not "setCallback".

使用 externC可避免导出的函数出现名称错误，以匹配导出的链接器符号，或使用FunctionMapper将Java方法名称映射到链接器符号。

Use extern "C" to avoid name mangling on exported functions, rename your Java function to match the exported linker symbol, or use a FunctionMapper to map the Java method name to the linker symbol.

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