#include <windows.h>    

LRESULT CALLBACK WndProc(HWND hWnd,UINT uMsg,WPARAM wParam,LPARAM lParam);
int WINAPI WinMain(   HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int   nCmdShow)    
{
  MSG     msg;
  WNDCLASS   wc;
  HWND hWnd;

  wc.style         = CS_HREDRAW | CS_VREDRAW;  
  wc.lpfnWndProc     = (WNDPROC) WndProc;          
  wc.cbClsExtra     = 0;                        
  wc.cbWndExtra     = 0;                        
  wc.hInstance     = hInstance;                  
  wc.hIcon         = LoadIcon(NULL, IDI_WINLOGO);        
  wc.hCursor         = LoadCursor(NULL, IDC_ARROW);    
  wc.hbrBackground   = (HBRUSH)GetStockObject(BLACK_BRUSH);                        
  wc.lpszMenuName     = NULL;                    
  wc.lpszClassName   = "Demo";    

  if (!RegisterClass(&wc))                        
  {
    MessageBox(NULL,"Failed To Register The Window Class.","ERROR",MB_OK|MB_ICONEXCLAMATION);
    return FALSE;                          
  }
  hWnd=CreateWindow(
                    "Demo",                
                    "Demo1",                                        
                    WS_OVERLAPPEDWINDOW,          
                    CW_USEDEFAULT,
                    CW_USEDEFAULT,                    
                    CW_USEDEFAULT,  
                    CW_USEDEFAULT,  
                    NULL,                  
                    NULL,                    
                    hInstance,            
                    NULL    
    );
  ShowWindow(hWnd,nCmdShow);
  UpdateWindow(hWnd);

  //这里为什么改成GetMessage(&msg,hWnd,0,0)程序就关不了了？    
  while(GetMessage(&msg,NULL,0,0))
  {
    TranslateMessage(&msg);
    DispatchMessage(&msg);
  }

  return (msg.wParam);                  
}

LRESULT CALLBACK WndProc(HWND hWnd,UINT uMsg,WPARAM wParam,LPARAM lParam)        
{
  switch (uMsg)                        
  {
    case WM_CLOSE:
        PostQuitMessage(0);          
        return 0;

    default:
        break;
  }

  return DefWindowProc(hWnd,uMsg,wParam,lParam);
}

如果将GetMessage中的第2个NULL参数改成和hWnd程序就关不了了，我查过MSDN上边讲当第2个参数是NULL时，表示为属于该程序的消息队列的所有窗口检索信息。但问题是，我这个程序里就只有一个窗口，用该窗口的句柄作为参数应该也可以吧。
望高手指点一二。

LZ这个程序,我执行试了试,如果运行完后窗口不动,直接关就关不掉,但是只要稍微拖动下窗口,让它UPDATE重画一次就可以关掉了...具体原因不清楚,我猜想是hWnd必须在进入了第1次消息循环后才获得当前窗口句柄.在此之前是个随机值吧.所以要UPDATE一下,发送一个PAINT消息让hWnd指向当前窗口.

我也运行了一下，确实是像楼主说的情况，LS说的有一定的道理的。

但问题是hWnd在我创建窗体的时候应该就已经得到具体的值了呀。

楼主喊我顶的
不关我的事

GetMessage() will return -1 if it encounters an error. Make sure you remember this, or it will catch you out at some point... even though GetMessage() is defined as returning a BOOL, it can return values other than TRUE or FALSE, since BOOL is defined as UINT (unsigned int). The examples of code like this while(GetMessage(&msg, NULL, 0, 0)) may seem to work, but will not process certian conditions correctly. So the correct way of doing this is while(GetMessage(&msg, NULL, 0, 0)>0), it will work perfectly well

Your problem is while you click button close, it will send a message WM_CLOSE to the message queue and then WM_DESTROY will also be post, what will actually destory the window is message WM_DESTORY, so it will not work while you click the close button with out handling the message WM_DESTORY. You should write like this:
switch (uMsg)
{
  case WM_CLOSE:
    DestroyWindow(hwnd);
    break;
  case WM_DESTORY:
    PostQuitMessage(0);
    return (0);   //this is not essential
  default:
    return DefWindowProc(hWnd, uMsg, wParam, lParam);
}

Remark: PostQuitMessage() is designed for message WM_DESTORY; while handling message WM_CLOSE you should use DestroyWindow() and do something else to free the memory, but windows XP has its own garbage collector.
To get rid of these complex message loop, you can use message analyser. in this way you need to "#include <windowx.h>"


[ 此贴被电子青蛙在2006-11-16 10:49重新编辑 ]

OK了,把GetMessage(...)改成GetMessage(...)>0就可以了