PeekMessage与GetMessage

BOOL PeekMessage(

  LPMSG lpMsg, 

  HWND hWnd, 

  UINT wMsgFilterMin, 

  UINT wMsgFilterMax, 

  UINT wRemoveMsg 

); 





BOOL GetMessage(

  LPMSG lpMsg, 

  HWND hWnd, 

  UINT wMsgFilterMin, 

  UINT wMsgFilterMax 

); 

参考msdn:

• PeekMessage: This function checks a thread message queue for a message and places the message (if any) in the specified structure.
• GetMessage: This function retrieves a message from the calling thread's message queue and places it in the specified structure. 

解释:

• 函数名:peek---偷看(没消息?我闪!),get---获取(没消息?我等!)
• 参数:PeekMessage比GetMessage多一个wRemoveMsg 参数(用于设置处理完后,是否从队列中移除消息).除了WM_PAINT消息外,GetMessage获取并移除所处理消息,而PeekMessage则可以通过参数设置是否移除所处理消息.
• 返回值:GetMessage---对WM_QUIT消息返回zero,其他消息返回nonzero.PeekMessage---有消息返回nonzero,无消息返回zero.

PeekMessage应用举例(见<Windows程序设计>):

/*----------------------------------------------------------------------

        

  RANDRECT.C --   Displays Random Rectangles

        

                (c) Charles Petzold, 1998

        

-----------------------------------------------------------------------*/

        

#include <windows.h>

        

#include <stdlib.h>// for the rand function

        



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

        

void DrawRectangle (HWND) ;

        



int cxClient, cyClient ;

        

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,

        

                   PSTR szCmdLine, int iCmdShow)

        

{

        

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

        

    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 ("This program requires Windows NT!"),

        

                                    szAppName, MB_ICONERROR) ;

        

            return 0 ;

        

    }

        

   

        

    hwnd = CreateWindow (szAppName, TEXT ("Random Rectangles"),

        

                           WS_OVERLAPPEDWINDOW,

        

                           CW_USEDEFAULT, CW_USEDEFAULT,

        

                           CW_USEDEFAULT, CW_USEDEFAULT,

        

                           NULL, NULL, hInstance, NULL) ;

        

   

        

    ShowWindow (hwnd, iCmdShow) ;

        

    UpdateWindow (hwnd) ;

        

   

        

    while (TRUE)

        

    {

        

            if (PeekMessage (&msg, NULL, 0, 0, PM_REMOVE))//有消息,处理消息,无消息,画随机矩形

        

            {

        

                   if (msg.message == WM_QUIT)//退出

        

                     break ;

        

                   TranslateMessage (&msg) ;

        

                   DispatchMessage (&msg) ;

        

        }

        

            else

        

                   DrawRectangle (hwnd) ;

        

    }

        

    return msg.wParam ;

        

}

        



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

        

{

        

    switch (iMsg)

        

    {

        

    case   WM_SIZE:

        

            cxClient = LOWORD (lParam) ;

        

            cyClient = HIWORD (lParam) ;

        

            return 0 ;

        

        

        

    case   WM_DESTROY:

        

            PostQuitMessage (0) ;

        

            return 0 ;

        

    }

        

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

        

}

        

void DrawRectangle (HWND hwnd)

        

{

        

    HBRUSHhBrush ;

        

    HDC           hdc ;

        

    RECT          rect ;

        

   

        

    if (cxClient == 0 || cyClient == 0)

        

            return ;

        

    SetRect (&rect, rand () % cxClient, rand () % cyClient,

        

                          rand () % cxClient, rand () % cyClient) ;

        

    hBrush = CreateSolidBrush (

        

                   RGB (rand () % 256, rand () % 256, rand () % 256)) ;

        

    hdc = GetDC (hwnd) ;

        

    FillRect (hdc, &rect, hBrush) ;

        

    ReleaseDC (hwnd, hdc) ;

        

    DeleteObject (hBrush) ;

        

}