Windows父子窗口的注册问题?为什么要注册两次啊?

[ldd20190327]

#include <windows.h>
#define DIVISIONS 5

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
LRESULT CALLBACK ChildWndProc(HWND, UINT, WPARAM, LPARAM);
TCHAR szChildClass[] = TEXT("Child");

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
PSTR szCmdLine, int iCmdShow)
{
static TCHAR szAppName[] = TEXT("Checker3");
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)GetStockObject(WHITE_BRUSH);
wndclass.lpszMenuName = NULL;
wndclass.lpszClassName = szAppName;

if (!RegisterClass(&wndclass))
{
MessageBox(NULL, TEXT("Program requires Windows NT!"),
szAppName, MB_ICONERROR);
return 0;
}
wndclass.lpfnWndProc = ChildWndProc;
wndclass.cbWndExtra = sizeof(long);
wndclass.hIcon = NULL;
wndclass.lpszClassName = szChildClass;
RegisterClass(&wndclass);
hwnd = CreateWindow(szAppName, TEXT("Checker3 Mouse Hit-Test 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)
{
static HWND hwndChild[DIVISIONS][DIVISIONS];
int cxBlock, cyBlock, x, y;
switch (message)
{
case WM_CREATE:
for (x = 0; x < DIVISIONS; x++)
for (y = 0; y < DIVISIONS; y++)
hwndChild[x][y] = CreateWindow(szChildClass, NULL,
WS_CHILDWINDOW | WS_VISIBLE,
0, 0, 0, 0,
hwnd, (HMENU)(y << 8 | x),
(HINSTANCE)GetWindowLong(hwnd, GWL_HINSTANCE),
NULL);
return 0;
case WM_SIZE:
cxBlock = LOWORD(lParam) / DIVISIONS;
cyBlock = HIWORD(lParam) / DIVISIONS;
for (x = 0; x < DIVISIONS; x++)
for (y = 0; y < DIVISIONS; y++)
MoveWindow(
hwndChild[x][y],
x * cxBlock, y * cyBlock,
cxBlock, cyBlock, TRUE);
return 0;
case WM_LBUTTONDOWN:
MessageBeep(0);
return 0;
case WM_DESTROY:
PostQuitMessage(0);
return 0;
}
return DefWindowProc(hwnd, message, wParam, lParam);
}
LRESULT CALLBACK ChildWndProc(HWND hwnd, UINT message,
WPARAM wParam, LPARAM lParam)
{
HDC hdc;
PAINTSTRUCT ps;
RECT rect;
switch (message)
{
case WM_CREATE:
SetWindowLong(hwnd, 0, 0); // on/off flag
return 0;
case WM_LBUTTONDOWN:
SetWindowLong(hwnd, 0, 1 ^ GetWindowLong(hwnd, 0));
InvalidateRect(hwnd, NULL, FALSE);
return 0;
case WM_PAINT:
hdc = BeginPaint(hwnd, &ps);
GetClientRect(hwnd, &rect);
Rectangle(hdc, 0, 0, rect.right, rect.bottom);
if (GetWindowLong(hwnd, 0))
{
MoveToEx(hdc, 0, 0, NULL);
LineTo(hdc, rect.right, rect.bottom);
MoveToEx(hdc, 0, rect.bottom, NULL);
LineTo(hdc, rect.right, 0);
}
EndPaint(hwnd, &ps);
return 0;
}
return DefWindowProc(hwnd, message, wParam, lParam);
}

谁能帮我解释下这个Windows程序中关于父子窗口的两次注册问题吗?

[zgl7903]

wndclass.lpfnWndProc = WndProc; wndclass.lpszClassName = szAppName; wndclass.lpfnWndProc = ChildWndProc; wndclass.lpszClassName = szChildClass; 两个窗口

[ldd20190327]

引用 1 楼 zgl7903 的回复:

wndclass.lpfnWndProc = WndProc; wndclass.lpszClassName = szAppName; wndclass.lpfnWndProc = ChildWndProc; wndclass.lpszClassName = szChildClass; 两个窗口

谢谢你啊,我突然间想通了感觉自己好笨啊