windows（3）修改窗口类实现文字的切换

【摘要】这节课的主要内容是将如何修改窗口类，也就是修改一个创建好的窗口类。本节课实现修改我们自己创建的窗口类，来达到闪烁的文字和窗口背景颜色的效果。当然也可以修改系统创建的窗口类。

修改窗口类，系统已经提供了API函数SetWindowLong。它可以修改已经创建的窗口的风格、窗口过程、窗口ID和窗口关联的数据。

修改的实现过程很简单。我们利用这个修改，可以随意切换窗口处理过程。只要修改一下窗口过程，窗口的消息就会发送到新的窗口过程中处理了。

首先，准备好一个窗口过程。自己提供的窗口过程中，包含了另外一套消息处理。和原先的窗口过程一起，一共有两套了。

然后通过使用SetWindowLong(hwnd, GWL_WNDPROC, (LONG)新窗口过程函数名)，这样就可以重新设置了。SetWindowLong需要设置的窗口句柄，所以，你要等开始的窗口已经创建成功了，才能设置，不然你无法获取窗口句柄咯。你也可以等窗口创建出来后再给窗口类修改窗口过程，也可以创建窗口后，修改窗口类的窗口过程，然后再显示窗口

#include <Windows.h>
#include <tchar.h>

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

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrev, PSTR szCmdLine, int iCmdShow)
{
static TCHAR szExeName[] = _T("Win32");
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 = szExeName;

if (!RegisterClass(&wndclass))
{
MessageBox(NULL, _T("注册窗口类失败，此程序需要运行在Windows NT平台下。"), szExeName, MB_ICONERROR);
return 0;
}

hwnd = CreateWindow(szExeName, _T("我的窗口标题_C++技术网"), WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hInstance, NULL);

SetWindowLong(hwnd, GWL_WNDPROC, (LONG)MyProc);
ShowWindow(hwnd, iCmdShow);
UpdateWindow(hwnd);

while (GetMessage(&msg, NULL, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return msg.wParam;
}
LRESULT CALLBACK MyProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
HDC hdc;
PAINTSTRUCT ps;
RECT rect;
static int i = 0;
WCHAR szTip[100] = { 0 };
switch (message)
{
case WM_CREATE:
MessageBox(NULL, _T("窗口正在创建"), _T("win32"), MB_ICONINFORMATION);
SetTimer(hwnd, 0, 1000, NULL);
return 0;
case WM_PAINT:
hdc = BeginPaint(hwnd, &ps);
GetClientRect(hwnd, &rect);
SetBkColor(hdc, RGB(0, 0, 255));
SetTextColor(hdc, RGB(255, 0, 0));
FillRect(GetWindowDC(hwnd), &rect, (HBRUSH)GetStockObject(WHITE_BRUSH));
DrawText(hdc, _T("Win32程序界面，初始化窗口过程"), -1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER);
SetWindowLong(hwnd, GWL_WNDPROC, (LONG)WndProc);//- 切换窗口过程
swprintf(szTip,100, _T("计时：%d"), i);
DrawText(hdc, szTip, -1, &rect, DT_SINGLELINE | DT_CENTER);
EndPaint(hwnd, &ps);
return 0;
case WM_DESTROY:
MessageBox(NULL, _T("程序即将结束！"), _T("win32"), MB_ICONINFORMATION);
KillTimer(hwnd, 0);
PostQuitMessage(0);
return 0;
case WM_TIMER:
GetClientRect(hwnd, &rect);
InvalidateRect(hwnd, &rect, true);
i++;
return 0;
}
return DefWindowProc(hwnd, message, wParam, lParam);
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
HDC hdc;
PAINTSTRUCT ps;
RECT rect;
static int i = 0;
WCHAR szTip[100] = { 0 };
switch (message)
{
case WM_CREATE:
MessageBox(NULL, _T("窗口正在创建"), _T("win32"), MB_ICONINFORMATION);
SetTimer(hwnd, 0, 1000, NULL);
return 0;
case WM_PAINT:
hdc = BeginPaint(hwnd, &ps);
GetClientRect(hwnd, &rect);
SetBkColor(hdc, RGB(0, 0, 255));
SetTextColor(hdc, RGB(255, 0, 0));
FillRect(GetWindowDC(hwnd), &rect, (HBRUSH)GetStockObject(WHITE_BRUSH));
DrawText(hdc, _T("Win32程序界面，初始化窗口过程"), -1, &rect, DT_SINGLELINE | DT_CENTER | DT_VCENTER);
SetWindowLong(hwnd, GWL_WNDPROC, (LONG)MyProc);//- 切换窗口过程
swprintf(szTip,100, _T("计时：%d"), i);
DrawText(hdc, szTip, -1, &rect, DT_SINGLELINE | DT_CENTER);
EndPaint(hwnd, &ps);
return 0;
case WM_DESTROY:
MessageBox(NULL, _T("程序即将结束！"), _T("win32"), MB_ICONINFORMATION);
KillTimer(hwnd, 0);
PostQuitMessage(0);
return 0;
case WM_TIMER:
GetClientRect(hwnd, &rect);
InvalidateRect(hwnd, &rect, true);
i++;
return 0;
}
return DefWindowProc(hwnd, message, wParam, lParam);
}

总结：SetWindowLong(hwnd, GWL_WNDPROC, (LONG)新窗口过程函数名)该函数可以修改窗口过程函数。一般来说，当一个窗口类创建的时候，窗口过程函数就随之确定。我们可以通过这个修改函数使窗口类执行另外的窗口过程函数。