PostThreadMessage的原型是這樣的
BOOL PostThreadMessage( DWORD idThread,
UINT Msg,
WPARAM wParam,
LPARAM lParam
);
PostThreadMessage可以用于線程之間的異步通訊，因?yàn)樗挥玫却{(diào)用者返回，
這也許是線程通訊中最簡單的一種方法了。
但是要注意以下問題
1 .PostThreadMessage有時(shí)會失敗，報(bào)1444錯(cuò)誤(Invalid thread identifier. )
其實(shí)這不一定是線程不存在的原因，也有可能是線程不存在消息隊(duì)列(message queue)造成的。
事實(shí)上，并不是每個(gè)thread都有message queue,那如何讓thread具有呢？
答案是，至少調(diào)用message相關(guān)的function一次，比如GetMessage,PeekMessage。
2.如果是post動態(tài)分配的memory給另外一個(gè)thread,要注意內(nèi)存的正確釋放。
3.PostThreadMessage不能夠post WM_COPYDATE之類的同步消息，否則會報(bào)錯(cuò)
4.最好不要使用PostThreadMessage post message給一個(gè)窗口,使用PostMessage替代。
下面是我寫的一個(gè)比較嚴(yán)整的例子，僅供參考。
#include <windows.h>
#include <cstdio>
#include <process.h>
#define MY_MSG WM_USER+100
const int MAX_INFO_SIZE = 20;
HANDLE hStartEvent; // thread start event
// thread function
unsigned __stdcall fun(void *param)
{
printf("thread fun start
\n");
MSG msg;
PeekMessage(&msg, NULL, WM_USER, WM_USER, PM_NOREMOVE);
if(!SetEvent(hStartEvent)) //set thread start event
{
printf("set start event failed,errno:%d\n",::GetLastError());
return 1;
}
while(true)
{
if(GetMessage(&msg,0,0,0)) //get msg from message queue
{
switch(msg.message)
{
case MY_MSG:
char * pInfo = (char *)msg.wParam;
printf("recv %s\n",pInfo);
delete[] pInfo;
break;
}
}
};
return 0;
}
int main()
{
HANDLE hThread;
unsigned nThreadID;
hStartEvent = ::CreateEvent(0,FALSE,FALSE,0); //create thread start event
if(hStartEvent == 0)
{
printf("create start event failed,errno:%d\n",::GetLastError());
return 1;
}
//start thread
hThread = (HANDLE)_beginthreadex( NULL, 0, &fun, NULL, 0, &nThreadID );
if(hThread == 0)
{
printf("start thread failed,errno:%d\n",::GetLastError());
CloseHandle(hStartEvent);
return 1;
}
//wait thread start event to avoid PostThreadMessage return errno:1444
::WaitForSingleObject(hStartEvent,INFINITE);
CloseHandle(hStartEvent);
int count = 0;
while(true)
{
char* pInfo = new char[MAX_INFO_SIZE]; //create dynamic msg
sprintf(pInfo,"msg_%d",++count);
if(!PostThreadMessage(nThreadID,MY_MSG,(WPARAM)pInfo,0))//post thread msg
{
printf("post message failed,errno:%d\n",::GetLastError());
delete[] pInfo;
}
::Sleep(1000);
}
CloseHandle(hThread);
return 0;
}