api中小弟我创建的listbox为什么不显示啊大哥大姐们帮帮小弟我吧

2012-12-19

api中我创建的listbox为什么不显示啊？？大哥大姐们帮帮我吧！我想单击鼠标左键显示列表，但却不行。把列表的cr

api中我创建的listbox为什么不显示啊？？大哥大姐们帮帮我吧！
我想单击鼠标左键显示列表，但却不行。把列表的createwindow（）那部分放进WM_CREATE中就可直接显示，为什么放入WM_LBUTTONDOWN中却不行？
代码如下：

#include <windows.h>
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     static TCHAR szAppName[] = TEXT ("Environ") ;
     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) (COLOR_WINDOW + 1) ;
     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 ("Environment List Box"),
                          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)
{
     static HWND  hwndList;
     int         cxChar, cyChar ;
     switch (message)
     {
     case WM_CREATE :
          cxChar = LOWORD (GetDialogBaseUnits ()) ;
          cyChar = HIWORD (GetDialogBaseUnits ()) ;
          return 0 ;
case WM_LBUTTONDOWN:
  hwndList = CreateWindow (TEXT ("listbox"), NULL,
          WS_CHILD | WS_VISIBLE | LBS_STANDARD,
          cxChar, cyChar * 3,
          cxChar * 16 + GetSystemMetrics (SM_CXVSCROLL),
          cyChar * 5,
          hwnd, 1,
          (HINSTANCE) GetWindowLong (hwnd, GWL_HINSTANCE),
          NULL) ;
return 0;

     case WM_DESTROY :
          PostQuitMessage (0) ;
          return 0 ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}

[解决办法]
原因还不知道，但可用SendMessage()避开：
#include <windows.h>
LRESULT CALLBACK WndProc (HWND, UINT, WPARAM, LPARAM) ;
int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     static TCHAR szAppName[] = TEXT ("Environ") ;
     HWND         hwnd ;
     MSG          msg ;
     WNDCLASS     wndclass ;

     wndclass.style         = CS_HREDRAW

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api中小弟我创建的listbox为什么不显示啊大哥大姐们帮帮小弟我吧