SetTimer在无窗口和有窗口线程的使用

最新推荐文章于 2023-07-16 02:44:25 发布

原创最新推荐文章于 2023-07-16 02:44:25 发布 · 4.7k 阅读

3 ·

CC 4.0 BY-SA版权

文章标签：

#timer #callback #null

windows 专栏收录该内容

6 篇文章

订阅专栏

本文探讨了在无窗口线程中使用SetTimer函数时遇到的问题：设置的计时器ID与接收到的消息中的ID不符。通过MSDN文档解释了这一现象的原因，并提供了代码示例。

今天犯了一个粗心的错误,在无窗口线程中,SetTimer中设置计时器ID,而WM_TIMER消息响应函数中得到的计时器ID却不是之前设置的计时器ID.

// 111902.cpp : Defines the entry point for the console application. // #include "stdafx.h" #include "windows.h" BOOL DispatchThreadMessage(MSG* pMsg); VOID CALLBACK OnTimerProc(HWND hwnd,UINT uMsg,UINT_PTR idEvent,DWORD dwTime); int main(int argc, char* argv[]) { printf("Hello World!/n"); ::SetTimer(NULL,1,1000,OnTimerProc); MSG msg; while (GetMessage(&msg, 0, 0, 0) > 0) { if (msg.hwnd == NULL && DispatchThreadMessage(&msg)) continue; TranslateMessage(&msg); DispatchMessage(&msg); } return 0; } BOOL DispatchThreadMessage(MSG* pMsg) { if(pMsg->message == 0x0113) { printf("DispatchThreadMessage: %6d/n",pMsg->wParam); return false; } return false; } VOID CALLBACK OnTimerProc(HWND hwnd,UINT uMsg,UINT_PTR idEvent,DWORD dwTime) { printf("OnTimerProc: %6d/n",idEvent); }

对应计时器ID的输出的是一个随机数字.

原来在msdn中

nIDEvent

[in] Specifies a nonzero timer identifier. If the hWnd parameter is NULL, and the nIDEvent does not match an existing timer then it is ignored and a new timer ID is generated. If the hWnd parameter is not NULL and the window specified by hWnd already has a timer with the value nIDEvent , then the existing timer is replaced by the new timer. When SetTimer replaces a timer, the timer is reset. Therefore, a message will be sent after the current time-out value elapses, but the previously set time-out value is ignored. If the call is not intended to replace an existing timer, nIDEvent should be 0 if the hWnd is NULL.

注:只有当hWnd参数为非空时,计时器的ID为设置的 nIDEvent, 系统为你自动生成一个计时器ID,可由返回时值获取.