如何传递java函数指针到c ++本地代码 [英] How to pass java function pointer to c++ native code

问题描述

我想从java（android）代码调用本地c ++方法，并传递一个java函数作为参数，所以我将能够保存的函数指针在c ++代码，并从本机代码激活它。

我选择在java中使用匿名类实现函数指针，我从java调用native函数如下：

  interface FunctionPtrHelper {
 bool function（String param）; 
  

}

  NativeFunc（param1，param2，new FunctionPtrHelper（）{
 public bool myFunction（String param）{
 // body of my function 
}}）;如何让swig / jni知道第三个参数（它实际上是一个类），并翻译它到c ++中的函数指针（将包含myFunction）？
 
如果不可能，是否有另一种方法将函数指针从java传递给c ++？
解决方案
您可以编写一个C ++接口和SWIG它作为导演类。然后可以在Java中实现接口。在Java中实例化实现对象，并将其传递给一个C ++方法，该方法接受指针或对接口的引用，C ++将能够调用回您的Java类。例如：
  // SWIGed C ++ 
 class IStringToBool 
 {
 public：
 virtual bool call（std :: string s）= 0; 
} 
 
 class IStringToBoolUser 
 {
 public：
 void setFunction（IStringToBool& function）; 
} 
  
然后：
  // Java 
 public class MyFunction implements IStringToBool {
 public bool call（String s）{
 // do something 
 return true ; 
} 
} 
  
文档：使用导演的跨语言多态性 
 
I want to call a native c++ method from java (android) code, and pass a java function as a parameter, so I will be able to save the function pointer in the c++ code, and activate it from the native code.

I chose to implement the function pointer in java using anonymous class, and I call the native function from java as following:
interface FunctionPtrHelper {
bool function(String param);
}
NativeFunc(param1,param2,new FunctionPtrHelper() {
public bool myFunction(String param) {
    //body of my function
}});
How can I make swig/jni know the 3rd param (which is actually a class) and translate it to a function pointer in c++ (that will contain'myFunction') ?

In case it is not possible, is there another way to pass a function pointer from java to c++?
解决方案
You can write a C++ interface and SWIG it as a "director" class.  Then you can implement the interface in Java.  Instantiate the implementation object in Java and pass it into a C++ method that takes a pointer or reference to the interface, and C++ will be able to call back into your Java class.  For example:
// SWIGed C++
class IStringToBool
{
public:
    virtual bool call(std::string s) = 0;
}

class IStringToBoolUser
{
public:
    void setFunction(IStringToBool &function);
}
And then:
// Java
public class MyFunction implements IStringToBool {
    public bool call(String s) {
        // do something
        return true;
    }
}
Documentation: Cross language polymorphism using directors

                        
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