来自 c++ 应用程序的 Java com.sun.jna 回调函数

Question

我有一个用C++写的DLL，我无法更改。它具有以下公开的功能

// c++ 
DllExport unsigned int ProcessMessage( char * in_message, USHORT in_message_length, char * connectionString, bool ( SendMessage)( char * connectionString, BYTE * payload, USHORT iPayloadSize )  );

我有一个需要调用此 DLL 函数的 Java 应用程序。我目前正在使用 java 库 com.sun.jna

// Java 
public class main {
    public interface CBlargAPI extends Library {
        interface sendMessage_t extends Callback {
            boolean invoke(String connectionString, Pointer payload, short iPayloadSize );
        }
        int ProcessMessage( byte[] in_message, short in_message_length, String connectionString, sendMessage_t SendMessage ) ; 
    }
    public static void main(String[] args) throws Exception 
    {
        // Override function thingy (#A) 
        CBlarg.sendMessage_t sendMessage_fn  = new CBlarg.sendMessage_t() {
            @Override
            public boolean invoke(String connectionString, Pointer payload, short iPayloadSize) {
                System.out.println("sendMessage_t: " )  ;
                return false; 
                }
            };         
        }
        CBlargAPI.INSTANCE.ProcessMessage( receivePacket.getData(), (short) receivePacket.getLength(), connectionString, sendMessage_fn ); 
    }
    // static member function (#B) 
    public static boolean SendUDPMessage( String connectionString, Pointer payload, short length )  {    
        // ToDo: I want to use this one. 
    }
}

目前，这适用于override function thingy (#A)，但我想改用static member function (#B)。我尝试了一些没有成功的事情，例如

// Errors with "cannot find symbol, symbol: class SendUDPMessage, location: class main" 
CBACnetAPI.sendMessage_t sendMessage_fn  = new main.SendUDPMessage();

我是一名主要的 c++ 程序员，很少接触 java

我的问题是：

• 如何将静态成员函数SendUDPMessage()调用为回调而不是Override function thingy (#A)？

Answer 1

你必须让override function thingy (#A)调用static member function(#B)。 Java 没有函数指针，因此您需要一个接口对象来达到此目的。

为什么你需要在 #A 上做 #B？