初学C++,通过一个小程序提几个问题!
猞猁狲 2004-12-26 11:12:01 程序是这样的:我要问的问题都加了注释!
#include<windows.h>
#include<string.h>
#include<stdlib.h>
#include<stdio.h>
LRESULT CALLBACK WndProc(HWND,UINT,WPARAM,LPARAM);
//请问上面的定义方法是什么意思定义常量、变量、结构体变量、不是这样的吗?如:int i 上面的定义怎么是LRESULT CALLBACK WndProc这样呢?具体解释一下,还有我还遇到过像这样的如:
hBrush=(HBRUSH)GetStockObject(DKGRAY_BRUSH),我的理解是调用一个函数取得句柄赋值给hBrush,可是函数前面又加个(HBRUSH)是什么意思呀?
int WINAPI WinMain //这里定义是怎么回事,定义一个整型的WINAPI还是WinMain呀?
(HINSTANCE hInstance,
HINSTANCE hPrevInst,
LPSTR lpszCmdLine,
int nCmdShow
)
{
HWND hwnd;
MSG msg;
WNDCLASS wndclass;
char lpszClassName[]="映像模式";
char lpszTitle[]="My_Map_Mode";
wndclass.style=0;
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=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(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;
HBRUSH hB1,hB2;
int nMode;
switch(message)
{
case WM_CREATE:
nMode=MM_TEXT;
case WM_LBUTTONDOWN:
nMode=MM_ISOTROPIC;
InvalidateRect(hwnd,NULL,1);
break;
case WM_RBUTTONDOWN:
nMode=MM_ANISOTROPIC;
InvalidateRect(hwnd,NULL,1);
break;
case WM_PAINT:
hdc=BeginPaint(hwnd,&ps);
SetMapMode(hdc,nMode);
SetWindowExtEx(hdc,150,150,NULL);
SetViewportExtEx(hdc,150,100,NULL);
SetViewportOrgEx(hdc,150,60,NULL);
hB1=GetStockObject(WHITE_BRUSH); //***********
hB2=GetStockObject(BLACK_BRUSH); //*********
SelectObject(hdc,hB2);
Ellipse(hdc,0,10,150,140);
EndPaint(hwnd,&ps);
break;
case WM_DESTROY:
DeleteObject(hB1);
DeleteObject(hB2);
PostQuitMessage(0);
break;
default:
return DefWindowProc(hwnd,message,wParam,lParam);
}
return 0;
}
以上我加星号的行都产生以下错误!不知道是什么意思!
C:\Program Files\Microsoft Visual Studio\MyProjects\TheC_SDK_2\TheC_SDK_2.cpp(92) : error C2440: '=' : cannot convert from 'void *' to 'struct HBRUSH__ *'
Conversion from 'void*' to pointer to non-'void' requires an explicit cast
C:\Program Files\Microsoft Visual Studio\MyProjects\TheC_SDK_2\TheC_SDK_2.cpp(93) : error C2440: '=' : cannot convert from 'void *' to 'struct HBRUSH__ *'
Conversion from 'void*' to pointer to non-'void' requires an explicit cast