<类中开启一个线程, 并和主线程用消息通讯>的代码, 为什么总报错..

[HoNooD]

想实现的功能是, 创建一个类(单例类, 这里简化了), 这个类创建的时候就开启一个新线程并立即执行. 该线程的任务是获取最新的数据, 并以消息形式通知主线程, 然后主线程更新类的成员变量.

我写的代码:

#include <iostream>
#include <stdio.h>
#include <windows.h>

using namespace std;

struct ExDataType
{
   int id;
   double value;
};

#define UM_DATA_ACQUIRE (WM_USER + 1001)

class A
{
public:
   A();
   void Update();
   void Show();
private:
   DWORD WINAPI ThreadFunc(LPVOID para);
   ExDataType m_data;
};

A::A()
{
   m_data.id = 0;
   m_data.value = 0.0;

   DWORD dwValue = GetCurrentThreadId();
   HANDLE hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)ThreadFunc, &dwValue, 0, NULL);
   if (!hThread)
   {
       std::cout << "error\r\n";
       exit(-1);
   }
   //CloseHandle(hThread);
}

void A::Update()
{
   MSG msg;
   ExDataType *pTmp = NULL;
   while(GetMessage(&msg, NULL, 0, 0))
   {
       pTmp = (ExDataType *)(msg.wParam);
       switch(msg.message)
       {
       case UM_DATA_ACQUIRE:
           m_data.id = pTmp->id;
           m_data.value = pTmp->value;
           break;
       default:
           break;
       }
   }
}

void A::Show()
{
   std::cout << "m_data.id: " << m_data.id << "\tm_data.value: " << m_data.value << "\r\n";
}

DWORD WINAPI A::ThreadFunc(LPVOID para)
{
   DWORD dwThreadId = *((DWORD *)para);
   ExDataType threadData = {0, 0.0};

   while(TRUE)
   {
       threadData.id += 2;
       threadData.value += 2.2;
       PostThreadMessage(dwThreadId, UM_DATA_ACQUIRE, (WPARAM)(&threadData), (LPARAM)0);
       Sleep(5000); 
   }

   return 0;
}

int main()
{
   A a;
   a.Show();

   return 0;
}

不明白创建线程那里的线程处理函数该怎么写, 另外, 这样能否正确实现我的目的? 请各位高手指教. 非常感谢!

[wocow3]

1.你这个是console程序，Post消息过来的时候主线程根本没有消息队列，post必然失败。。
A的构造函数调一下PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE);
2.写了Update为何不调用，那怎么处理消息。。

[灌水九段]

Update没调用
a.show白忙活

[HoNooD]

修改了, 可数据还是更新不了...

#include <iostream>
using namespace std;
#include <stdio.h>
#include <windows.h>

#define UM_DATA_GET (WM_USER + 1001)

struct ExDataType
{
    int id;
    double value;
};

DWORD WINAPI Thread_Update(LPVOID para);
DWORD WINAPI Thread_GetData(LPVOID para);

CRITICAL_SECTION g_cs;

class A
{
public:
    A();
    void Show();
private:
    DWORD m_threadID;
    ExDataType m_data;
};

A::A() : m_threadID(0)
{
    m_data.id = 1;
    m_data.value = 1.1; 

    HANDLE hThread_Update = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)Thread_Update, (LPVOID)(&m_data), 0, &m_threadID);
    if (!hThread_Update)
    {
        std::cout << "error 1\r\n";
        exit(-1);
    }
    CloseHandle(hThread_Update);

    HANDLE hThread_GetData = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)Thread_GetData, (LPVOID)(&m_threadID), 0, NULL);
    if (!hThread_GetData)
    {
        std::cout << "error 2\r\n";
        exit(-2);
    }
    CloseHandle(hThread_GetData); 
}

void A::Show()
{
    EnterCriticalSection(&g_cs);
    std::cout << "m_data.id: " << m_data.id << "\tm_data.value: " << m_data.value << "\r\n";
    LeaveCriticalSection(&g_cs);
}

DWORD WINAPI Thread_GetData(LPVOID para)
{
    DWORD dwThreadId = *(DWORD *)para;
    ExDataType threadData = {0, 0.0};
    BOOL ret;

    while(TRUE)
    {
        threadData.id += 2;
        threadData.value += 2.2;
        ret = PostThreadMessage(dwThreadId, UM_DATA_GET, (WPARAM)(&threadData), (LPARAM)0);
        Sleep(1000); 
    }

    return 0; 
}

DWORD WINAPI Thread_Update(LPVOID para)
{
    ExDataType data = *(ExDataType *)para;
    MSG msg;
    ExDataType *pTmp = NULL;

    while(TRUE)
    {
        if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) /* GetMessage(&msg, NULL, 0, 0) */
        {
            EnterCriticalSection(&g_cs);
            pTmp = (ExDataType *)(msg.wParam);
            switch(msg.message)
            {
            case UM_DATA_GET:
                data.id = pTmp->id;
                data.value = pTmp->value;
                break;
            default:
                break;
            }
            LeaveCriticalSection(&g_cs);
        }
    }

    return 0;
}

int main()
{
    InitializeCriticalSection(&g_cs);
    A a;
    int count = 0; 
    while (5 > count++)
    {
        a.Show();
        Sleep(1000);
    }

    DeleteCriticalSection(&g_cs);
    return 0;
}

[HoNooD]

问题查出来了: 虽然传进来的参数是需要更新数据的指针, 但线程函数里面定义了一个局部变量, 更新的只是局部变量.

哎, 太粗心了. 写C语言的函数时这样的错误很少, 到C++里就晕菜了.

感谢楼上回贴的各位朋友!

[wocow3]

ThreadFunc先改成静态成员函数再说。。

[HoNooD]

[Quote=引用 1 楼 wocow3 的回复:]
ThreadFunc先改成静态成员函数再说。。
[/Quote]
代码改了, 可是要更新的数据总无法更新.
跟了下, 从线程发送信息总失败, 好像是它获得的主线程ID有误, 但不明白这么写哪里错了...

[HoNooD]

修改后的代码在这里:

#include <iostream>
#include <stdio.h>
#include <windows.h>
#include <ctime>

using namespace std;

#define UM_DATA_ACQUIRE (WM_USER + 1001)

struct ExDataType
{
    int id;
    double value;
};

DWORD WINAPI ThreadFunc(LPVOID para);

class A
{
public:
    A();
    void Update();
    void Show();
private:
    ExDataType m_data;
};

A::A()
{
    m_data.id = 1;
    m_data.value = 1.1;

    DWORD dwValue = GetCurrentThreadId();
    HANDLE hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)ThreadFunc, &dwValue, 0, NULL);
    if (!hThread)
    {
        std::cout << "error\r\n";
        exit(-1);
    }
    CloseHandle(hThread);
}

void A::Update()
{
    MSG msg;
    ExDataType *pTmp = NULL;
    while(GetMessage(&msg, NULL, 0, 0))
    {
        pTmp = (ExDataType *)(msg.wParam);
        switch(msg.message)
        {
        case UM_DATA_ACQUIRE:
            m_data.id = pTmp->id;
            m_data.value = pTmp->value;
            break;
        default:
            break;
        }
    }
}

void A::Show()
{
    std::cout << "m_data.id: " << m_data.id << "\tm_data.value: " << m_data.value << "\r\n";
}

DWORD WINAPI ThreadFunc(LPVOID para)
{
    DWORD dwThreadId = *(DWORD *)para;
    ExDataType threadData = {0, 0.0};
    BOOL ret;

    while(TRUE)
    {
        threadData.id += 2;
        threadData.value += 2.2;
        ret = PostThreadMessage(dwThreadId, UM_DATA_ACQUIRE, (WPARAM)(&threadData), (LPARAM)0);
        Sleep(1000); 
    }

    return 0;
}

int main()
{
    A a;
    int count = 0;
    while (5 > count++)
    {
        a.Show();
        Sleep(1000);
    }

    return 0;
}