Windows程序设计：计时器

我们可以通过调用SetTimer函数建立一个计时器。SetTimer函数有一个时间间隔范围为1~4294967295毫秒(将近50天)的整型参数，这个值指示windows每隔一定时间给您的出现发送一个WM_TIMER消息。

在Windows98中，计时器具有55毫秒的分辨率。在Windows NT中，计时器具有10毫秒的分辨率。Windows不能以高于这一分辨率的速度接受WM_TIMER消息。

SetTimer函数使用方法如下：
SetTimer(hwnd, 1, uiMsecInterval, NULL);

第一个参数是其窗口过程将要接受WM_TIMER消息的窗口的句柄。第二个参数是计时器ID，他是一个非0数。第三个参数是一个32位无符号整数，以毫秒为单位指定一个时间间隔。第四个参数为回调函数的地址，若为NULL，则用默认的WndProc。也可以另外指定回叫函数：
SetTimer(hwnd, 1, uiMsecInterval, TimerProc);

回叫函数TimerProc可定义如下：
VOID CALLBACK TimerProc (HWND hwnd, UINT message, UINT iTimerID, DWORD dwTime){}

我们可以调用KillTimer (hwnd, ID_TIMER)在任何时刻停止计时器。

下面的例子，按秒刷新，显示当前时间：

#include <windows.h>

#define ID_TIMER    1

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,

                    PSTR szCmdLine, int iCmdShow)

{

     static TCHAR szAppName[] = TEXT ("DigClock") ;

     HWND         hwnd ;

     MSG          msg ;

     WNDCLASS     wndclass ;

     wndclass.style         = CS_HREDRAW | CS_VREDRAW ;

     wndclass.lpfnWndProc   = WndProc ;

     wndclass.cbClsExtra    = 0 ;

     wndclass.cbWndExtra    = 0 ;

     wndclass.hInstance     = hInstance ;

     wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;

     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;

     wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;

     wndclass.lpszMenuName  = NULL ;

     wndclass.lpszClassName = szAppName ;

     if (!RegisterClass (&wndclass))

     {

          MessageBox (NULL, TEXT ("Program requires Windows NT!"), 

                      szAppName, MB_ICONERROR) ;

          return 0 ;

     }

     hwnd = CreateWindow (szAppName, TEXT ("Clock"),

                          WS_OVERLAPPEDWINDOW,

                          CW_USEDEFAULT, CW_USEDEFAULT,

                          CW_USEDEFAULT, CW_USEDEFAULT,

                          NULL, NULL, hInstance, NULL) ;

     ShowWindow (hwnd, iCmdShow) ;

     UpdateWindow (hwnd) ;

     while (GetMessage (&msg, NULL, 0, 0))

          {

          TranslateMessage (&msg) ;

          DispatchMessage (&msg) ;

          }

     return msg.wParam ;

     }

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)

{

     HDC           hdc ;

     PAINTSTRUCT   ps ;

     TCHAR         szBuffer [10] ;

     switch (message)

     {

     case WM_CREATE:

          SetTimer (hwnd, ID_TIMER, 1000, NULL) ;

     case WM_TIMER:

          InvalidateRect (hwnd, NULL, TRUE) ;

          return 0 ;

     case WM_PAINT:

          hdc = BeginPaint (hwnd, &ps) ;

          SYSTEMTIME st ;      

          GetLocalTime (&st) ; //获取当前时间

          //格式化时间

          GetTimeFormat(LOCALE_SYSTEM_DEFAULT, TIME_FORCE24HOURFORMAT, &st, NULL, szBuffer, 10);

          //在屏幕上输出显示时间

          TextOut (hdc,0,0,szBuffer,8);

          EndPaint (hwnd, &ps) ;

          return 0 ;

     case WM_DESTROY:

          KillTimer (hwnd, ID_TIMER) ;

          PostQuitMessage (0) ;

          return 0 ;

     }

     return DefWindowProc (hwnd, message, wParam, lParam) ;

}

使用回叫函数TimerProc的版本：

#include <windows.h>

#define ID_TIMER    1

LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;

VOID CALLBACK TimerProc (HWND hwnd, UINT message, UINT iTimerID, DWORD dwTime);

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,

                    PSTR szCmdLine, int iCmdShow)

{

     static TCHAR szAppName[] = TEXT ("DigClock") ;

     HWND         hwnd ;

     MSG          msg ;

     WNDCLASS     wndclass ;

     wndclass.style         = CS_HREDRAW | CS_VREDRAW ;

     wndclass.lpfnWndProc   = WndProc ;

     wndclass.cbClsExtra    = 0 ;

     wndclass.cbWndExtra    = 0 ;

     wndclass.hInstance     = hInstance ;

     wndclass.hIcon         = LoadIcon (NULL, IDI_APPLICATION) ;

     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;

     wndclass.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;

     wndclass.lpszMenuName  = NULL ;

     wndclass.lpszClassName = szAppName ;

     if (!RegisterClass (&wndclass))

     {

          MessageBox (NULL, TEXT ("Program requires Windows NT!"), 

                      szAppName, MB_ICONERROR) ;

          return 0 ;

     }

     hwnd = CreateWindow (szAppName, TEXT ("Clock"),

                          WS_OVERLAPPEDWINDOW,

                          CW_USEDEFAULT, CW_USEDEFAULT,

                          CW_USEDEFAULT, CW_USEDEFAULT,

                          NULL, NULL, hInstance, NULL) ;

     ShowWindow (hwnd, iCmdShow) ;

     UpdateWindow (hwnd) ;

     while (GetMessage (&msg, NULL, 0, 0))

          {

          TranslateMessage (&msg) ;

          DispatchMessage (&msg) ;

          }

     return msg.wParam ;

     }

LRESULT CALLBACK WndProc (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)

{

     switch (message)

     {

     case WM_CREATE:

          SetTimer (hwnd, ID_TIMER, 1000, TimerProc) ;

          return 0;

     case WM_DESTROY:

          KillTimer (hwnd, ID_TIMER) ;

          PostQuitMessage (0) ;

          return 0 ;

     }

     return DefWindowProc (hwnd, message, wParam, lParam) ;

}

VOID CALLBACK TimerProc (HWND hwnd, UINT message, UINT iTimerID, DWORD dwTime)

{

    HDC hdc;

    TCHAR         szBuffer [10] ;

    hdc = GetDC(hwnd);

    SYSTEMTIME st ;      

    GetLocalTime (&st) ;

    GetTimeFormat(LOCALE_SYSTEM_DEFAULT, TIME_FORCE24HOURFORMAT, &st, NULL, szBuffer, 10);

    TextOut (hdc,0,0,szBuffer,8);

    ReleaseDC(hwnd, hdc);

}

函数GetTimeFormat用于格式化输出时间。

来源：CSDN

作者：albon_arith

链接：https://blog.csdn.net/hustspy1990/article/details/4778937