关于实例句柄(hInstance)的问题

Question

#include <windows.h>
#include "resource.h"

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

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     TCHAR    szAppName[] = TEXT ("IconDemo") ;
     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 (hInstance, MAKEINTRESOURCE (IDI_ICON)) ;
     wndclass.hCursor       = LoadCursor (hInstance,MAKEINTRESOURCE (IDC_CURSOR)) ;
     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 ("Icon Demo"),
                          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 ;
     
     switch (message)
     {          
     case WM_PAINT :
          hdc = BeginPaint (hwnd, &ps) ;      
               EndPaint (hwnd, &ps) ;
               return 0 ;
               
     case WM_DESTROY :
          PostQuitMessage (0) ;
          return 0 ;
     }
     return DefWindowProc (hwnd, message, wParam, lParam) ;
}

这是一个比较简单的win32程序

 

  wndclass.hIcon         = LoadIcon (hInstance, MAKEINTRESOURCE (IDI_ICON)) ;

     wndclass.hCursor       = LoadCursor (hInstance,MAKEINTRESOURCE (IDC_CURSOR)) ;

这两句中的hInstance为什么要指定呢，我不指定的话会有意外吗？

 

Answer 1

hInstance [in]

Handle to an instance of the module whose executable file contains the icon to be loaded. This parameter must be NULL when a standard icon is being loaded.

---

Visual C++ enthusiast, like network programming and driver development. At present is being engaged in the WinCE/Windows Mobile platform embedded development.

Answer 2

这个位置的参数是为了标识从哪个进程中加载资源

你可以不指定

那样会加载系统默认的