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。