[英]PostThreadMessage doesn't work
我有一個事件處理線程類,它允許我從其他線程引發事件而不會中斷它們的操作。 當析構函數被調用時,我向該線程發送一個退出消息,但它的消息循環似乎沒有收到此消息。
#include <iostream>
using namespace std;
#include <windows.h>
#define WIN32_LEAN_AND_MEAN
#define ET_EVENTPUSH 7854
#define ET_QUITLOOP 6581
#define EVENT_HANDLER void
typedef void (*EVENT)(LPVOID);
//# event handler thread
class event_thread
{
private:
//vars
HANDLE m_thread; //event loop thread
DWORD m_id; //thread id
//thread procedure
static DWORD WINAPI listener_loop(LPVOID);
public:
//constructor
event_thread();
~event_thread();
//functions
void push_event(EVENT, LPVOID);
};
//# event handler thread
event_thread::event_thread()
{
//create thread
m_thread = CreateThread(NULL, 0, listener_loop, NULL, 0, &m_id);
}
event_thread::~event_thread()
{
DWORD dw;
//stop thread
if (m_thread)
{
dw = GetLastError();
PostThreadMessage(m_id, ET_QUITLOOP, 0, 0);
dw = GetLastError();
WaitForSingleObject(m_thread, INFINITE);
CloseHandle(m_thread);
}
}
void event_thread::push_event(EVENT e, LPVOID p)
{
PostThreadMessage(m_id, ET_EVENTPUSH, (UINT)e, (UINT)p);
}
DWORD WINAPI event_thread::listener_loop(LPVOID param)
{
MSG msg;
#define event_type msg.message
#define event_call ((EVENT)(msg.wParam))
#define event_param (LPVOID)(msg.lParam)
//while thread is alive
while (GetMessage(&msg, NULL, 0, 0))
{
switch (event_type)
{
case ET_EVENTPUSH:
event_call(event_param);
break;
case ET_QUITLOOP:
return 0;
}
}
return 0;
}
EVENT_HANDLER asda(LPVOID as)
{
cout << (int)as << endl;
}
int main()
{
event_thread thr;
int i = 1;
while (!GetAsyncKeyState(VK_NUMPAD1))
{
thr.push_event(asda, (LPVOID)(i++));
Sleep(20);
}
return 0;
}
發送退出消息時, GetMessage
不會返回。 在PostThreadMessage
調用之后使用GetLastError()
給出1444 ERROR_INVALID_THREAD_ID
。
我不想使用PeekMessage
因為它使用100%CPU,也不想Sleep
因為它顯然是不好的做法 。
謝謝
ERROR_INVALID_THREAD_ID
表示您嘗試將消息發布到沒有消息隊列的線程ID。 所以要么你試圖在線程消息循環運行之前發布,要么在線程已經終止之后發布。
當你的線程開始運行時,它應首先向自己發布消息以創建消息隊列,然后設置一個信號以指示它已准備好接收消息,然后最終進入其消息循環。 在類構造函數中,在調用CreateThread()
,它可以在退出之前等待該信號。
嘗試這個:
#include <iostream>
using namespace std;
#include <windows.h>
#define WIN32_LEAN_AND_MEAN
#define ET_START WM_USER+1
#define ET_EVENTPUSH WM_USER+2
#define ET_QUITLOOP WM_USER+3
#define EVENT_HANDLER void
typedef void (*EVENT)(LPVOID);
//# event handler thread
class event_thread
{
private:
//vars
HANDLE m_thread; //event loop thread
DWORD m_id; //thread id
bool m_ready; // message queue is ready
//thread procedure
static DWORD WINAPI listener_loop(LPVOID);
public:
//constructor
event_thread();
~event_thread();
//functions
bool push_event(EVENT, LPVOID);
};
//# event handler thread
event_thread::event_thread()
{
//create thread
m_ready = false;
m_thread = CreateThread(NULL, 0, &listener_loop, this, 0, &m_id);
if (m_thread)
{
while (!m_ready)
Sleep(10);
}
}
event_thread::~event_thread()
{
//stop thread
if (m_thread)
{
if (!PostThreadMessage(m_id, ET_QUITLOOP, 0, 0))
{
DWORD dw = GetLastError();
...
}
WaitForSingleObject(m_thread, INFINITE);
CloseHandle(m_thread);
}
}
bool event_thread::push_event(EVENT e, LPVOID p)
{
return PostThreadMessage(m_id, ET_EVENTPUSH, (WPARAM)e, (LPARAM)p);
}
DWORD WINAPI event_thread::listener_loop(LPVOID param)
{
event_thread *pThis = (event_thread*)param;
MSG msg;
#define event_type msg.message
#define event_call ((EVENT)(msg.wParam))
#define event_param (LPVOID)(msg.lParam)
PostThreadMessage(pThis->m_id, ET_START, 0, 0);
pThis->m_ready = true;
//while thread is alive
while (GetMessage(&msg, NULL, 0, 0) > 0)
{
switch (event_type)
{
case ET_EVENTPUSH:
event_call(event_param);
break;
case ET_QUITLOOP:
PostQuitMessage(0);
break;
}
}
return 0;
}
如果您不喜歡Sleep()
循環,可以將m_ready
替換為可等待的事件,然后使用SetEvent()
和WaitForSingleObject()
。
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