窗口破坏过程与Windows消息循环

从用户单击关闭按钮（标题栏最右边）或者用鼠标或鍵盘选择系统菜单的“关闭”选项，直到窗口消失，应用程序结束。这期间到底发生了什么呢？这曾经是我百思不得其解的问题，我想也会有很多人和我一样会碰到这个问题。所以我要把我的一些学习心得写出来，与大家共享：  
  1、首先会产生一个WM_SYSCOMMAND消息，如果程序员没有对此消息进行拦截，则由缺省的窗口函数DefWindowProc进行处理，如果表达式(LOWORD(wParam)&0xFFF0)==SC_CLOSE   成立，DefWindowProc发出一个WM_CLOSE消息。  
  2、同样，如果程序员没有对WM_CLOSE消息进行拦截，则还是由DefWindowProc进行处理，这次，她只简单的调用 DestroyWindow函数，DestroyWindow先把窗口破坏掉，使用户看不到窗口。但是窗口破坏后，应用程序并没有结束，于是 DestroyWindow再接再励，送出了一个WM_DESTROY消息。  
  3、这一次，WM_DESTROY被载获了，通常是会有这样的句子：  
  case   WM_DESTROY:  
  PostQuitMessage(0);  
  ...  
  这里PostQuitMessage函数很简单的发送一个WM_QUIT消息来响应WM_DESTROY  
  4、WM_QUIT消息非常特殊，她使GetMessage函数返回0,从而结束了消息循环，  
  应用程序从此结束。  
  下面我给出完整的证明程序，请大家一试：  
  #include   <Windows.h>  
  #include   <TCHAR.h>  
  LRESULT   CALLBACK   WndProc(HWND,UINT,WPARAM,LPARAM);  
          int   WINAPI   WinMain(HINSTANCE   hInstance,  
                                        HINSTANCE   hPrevInst,  
                                        LPSTR           lpszCmdLine,  
                                        int                 nCmdShow)  
  {  
          HWND   hwnd;  
          MSG   Msg;  
          WNDCLASS   wndclass;  
          char   lpszClassName[]="窗口";  
          char   lpszTitle[]="窗口示例";  
          wndclass.style=CS_HREDRAW   |   CS_VREDRAW;  
          wndclass.lpfnWndProc   =WndProc;  
          wndclass.cbWndExtra=0;  
          wndclass.cbClsExtra   =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=lpszClassName;  
          if(!RegisterClass(&wndclass))  
          {  
                  MessageBeep(0);  
                  return   FALSE;  
          }  
          hwnd=CreateWindow(lpszClassName,  
                                      lpszTitle,  
                                      WS_OVERLAPPEDWINDOW,  
                                              CW_USEDEFAULT,  
                                      CW_USEDEFAULT,  
                                                      CW_USEDEFAULT,  
                                                      CW_USEDEFAULT,  
                              NULL,  
                              NULL,  
                              hInstance,  
                              NULL);  
          ShowWindow(hwnd,nCmdShow);  
          UpdateWindow(hwnd);  
          while(1)  
          {  
                  GetMessage(&Msg,NULL,0,0);  
                  if(Msg.message==WM_QUIT)  
                  {  
                          MessageBox(NULL,_T("收到WM_QUIT,即将跳出消息循环"),_T("注意了"),MB_OK);  
                          break;  
                  }  
                  TranslateMessage(&Msg);  
                  DispatchMessage(&Msg);  
          }  
                  MessageBox(NULL,_T("已经跳出消息循环，应用程序即将结束！"),_T("注意了"),MB_OK);  
          return   Msg.wParam;  
  }  
  LRESULT   CALLBACK   WndProc(  
                                                    HWND   hwnd,  
                                                    UINT   message,  
                                                    WPARAM   wParam,  
                                                    LPARAM   lParam)  
  {    
          switch(message)  
          {  
  case   WM_CLOSE:  
            MessageBox(NULL,_T("收到WM_CLOSE消息，即将调用   DestroyWindow(hwnd);"),_T("注意了"),MB_OK);  
            DestroyWindow(hwnd);  
            break;          
  case   WM_DESTROY:  
                  MessageBox(NULL,_T("已调用过DestroyWindow(hwnd)，看不到窗口了吧;"),_T("注意了"),MB_OK);  
          MessageBox(NULL,_T("以下处理WM_DESTROY"),_T("注意了"),MB_OK);  
          PostQuitMessage(0);  
          break;  
  case   WM_SYSCOMMAND:  
          if((LOWORD(wParam)&0xFFF0)==SC_CLOSE)  
          {  
                        MessageBox(NULL,_T("你关闭了窗口,即将发送WM_CLOSE消息！"),_T("注意了"),MB_OK);  
                SendMessage(hwnd,WM_CLOSE,0,0);  
          }  
          //不要添加   break，否则不能响应其它WM_SYSCOMMAND消息  
  default:  
        return   DefWindowProc(hwnd,message,wParam,lParam);  
          }  
          return(0);  
  }  
   
  --------------------------------------------------------------------------------  
  窗口破坏过程与Windows消息循环的补充，增加了对WM_NCDESTROY的处理  
  /**  
  *         File   Name                 :         MessageTest.cpp  
  *         Version                 :         1.1  
  *         Project   Name         :         MessageTest  
  *         Project   Type         :         Win32  
  *         Author                 :       netcoder  
  *                 Addition                           :         此版本增加了对WM_NCDESTROY的处理，   感谢   lily311   的补充    
  */  
   
  #include   <windows.h>  
  #include   <tchar.h>  
   
   
  LRESULT   CALLBACK   WndProc(HWND,UINT,WPARAM,LPARAM);  
  int   WINAPI   WinMain(HINSTANCE   hInstance,HINSTANCE   hPrevInst,LPSTR   lpszCmdLine,int   nCmdShow)  
  {  
          HWND   hwnd;  
          MSG   Msg;  
          WNDCLASS   wndclass;  
          char   lpszClassName[]="窗口";  
          char   lpszTitle[]="窗口示例";  
          wndclass.style=CS_HREDRAW   |   CS_VREDRAW;  
          wndclass.lpfnWndProc   =WndProc;  
          wndclass.cbWndExtra=0;  
          wndclass.cbClsExtra   =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=lpszClassName;  
          if(!RegisterClass(&wndclass))  
          {  
                  MessageBeep(0);  
                  return   FALSE;  
          }  
          hwnd=CreateWindow(lpszClassName,  
                                              lpszTitle,  
                                              WS_OVERLAPPEDWINDOW,  
                                              CW_USEDEFAULT,                              
                                              CW_USEDEFAULT,                                                
                                              CW_USEDEFAULT,                                                  
                                              CW_USEDEFAULT,  
                                              NULL,  
                                              NULL,  
                                              hInstance,  
                                              NULL);  
          ShowWindow(hwnd,nCmdShow);  
          UpdateWindow(hwnd);  
          while(1)  
          {  
                  GetMessage(&Msg,NULL,0,0);  
                  if(Msg.message==WM_QUIT)  
                  {  
                          MessageBox(NULL,_T("收到WM_QUIT,即将跳出消息循环"),_T("注意了"),MB_OK);  
                          break;  
                  }  
                  TranslateMessage(&Msg);  
                  DispatchMessage(&Msg);  
          }  
                  MessageBox(NULL,_T("已经跳出消息循环，应用程序即将结束！"),_T("注意了"),MB_OK);  
                  return   Msg.wParam;  
  }  
  LRESULT   CALLBACK   WndProc(                          
            HWND   hwnd,                          
            UINT   message,          
            WPARAM   wParam,                                          
            LPARAM   lParam)  
          {    
                  switch(message)  
                  {  
                  case   WM_CLOSE:  
                          MessageBox(NULL,_T("收到WM_CLOSE消息，即将调用   DestroyWindow(hwnd);"),_T("注意了"),MB_OK);  
                          DestroyWindow(hwnd);  
                          break;  
   
                  case   WM_DESTROY:  
                          MessageBox(NULL,_T("已收到WM_DESTROY,看不到窗口了吧!"),_T("注意了"),MB_OK);  
                          break;  
   
                  case   WM_NCDESTROY:  
                          MessageBox(NULL,_T("收到WM_NCDESTROY!"),_T("注意了"),MB_OK);  
                          PostQuitMessage(0);  
                          break;  
   
                  case   WM_SYSCOMMAND:  
                          if((LOWORD(wParam)&0xFFF0)==SC_CLOSE)  
                          {  
                                  MessageBox(NULL,_T("你关闭了窗口,即将发送WM_CLOSE消息！"),_T("注意了"),MB_OK);          
                                  SendMessage(hwnd,WM_CLOSE,0,0);  
                          }  
                          //不要添加   break，否则不能响应其它WM_SYSCOMMAND消息  
                  default:  
                          return           DefWindowProc(hwnd,message,wParam,lParam);  
                  }  
                  return(0);

本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/azhang00000/archive/2009/03/05/3961231.aspx

 

LRESULT CMyDlg::WindowProc(UINT message, WPARAM wParam, LPARAM lParam) 
{
    switch(message)   
    {   
    case   WM_CLOSE:   
        MessageBox(_T("收到WM_CLOSE消息，即将调用   DestroyWindow(hwnd);"),_T("注意了"),MB_OK);   
        DestroyWindow();   
        break;   
    case   WM_DESTROY:   
        MessageBox(_T("已调用过DestroyWindow(hwnd)，看不到窗口了吧;"),_T("注意了"),MB_OK);   
        MessageBox(_T("以下处理WM_DESTROY"),_T("注意了"),MB_OK);   
        PostQuitMessage(0);
        break;   
    case   WM_SYSCOMMAND:   
        if((LOWORD(wParam)&0xFFF0) == SC_CLOSE)   
        {    
            MessageBox(_T("你关闭了窗口,即将发送WM_CLOSE消息！"),_T("注意了"),MB_OK);   
            SendMessage(WM_CLOSE,0,0);   
        }    
        //不要添加   break，否则不能响应其它WM_SYSCOMMAND消息 
    }     
    return CDialog::WindowProc(message, wParam, lParam);
}