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MFC Messages and Events

    Question

  • Hi Guys

    please am studying MFC programming online. part of the tutorial we created a win32 project, then added a .cpp source file to it. below is both files

    /* the win32 .cpp file */

    // Win32MessagesandEvents.cpp : Defines the entry point for the application.
    //

    #include "stdafx.h"
    #include "Win32MessagesandEvents.h"

    #define MAX_LOADSTRING 100

    // Global Variables:
    HINSTANCE hInst;                                // current instance
    WCHAR szTitle[MAX_LOADSTRING];                  // The title bar text
    WCHAR szWindowClass[MAX_LOADSTRING];            // the main window class name

    // Forward declarations of functions included in this code module:
    ATOM                MyRegisterClass(HINSTANCE hInstance);
    BOOL                InitInstance(HINSTANCE, int);
    LRESULT CALLBACK    WndProc(HWND, UINT, WPARAM, LPARAM);
    INT_PTR CALLBACK    About(HWND, UINT, WPARAM, LPARAM);

    int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
                         _In_opt_ HINSTANCE hPrevInstance,
                         _In_ LPWSTR    lpCmdLine,
                         _In_ int       nCmdShow)
    {
        UNREFERENCED_PARAMETER(hPrevInstance);
        UNREFERENCED_PARAMETER(lpCmdLine);

        // TODO: Place code here.

        // Initialize global strings
        LoadStringW(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING);
        LoadStringW(hInstance, IDC_WIN32MESSAGESANDEVENTS, szWindowClass, MAX_LOADSTRING);
        MyRegisterClass(hInstance);

        // Perform application initialization:
        if (!InitInstance (hInstance, nCmdShow))
        {
            return FALSE;
        }

        HACCEL hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_WIN32MESSAGESANDEVENTS));

        MSG msg;

        // Main message loop:
        while (GetMessage(&msg, nullptr, 0, 0))
        {
            if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
            {
                TranslateMessage(&msg);
                DispatchMessage(&msg);
            }
        }

        return (int) msg.wParam;
    }



    //
    //  FUNCTION: MyRegisterClass()
    //
    //  PURPOSE: Registers the window class.
    //
    ATOM MyRegisterClass(HINSTANCE hInstance)
    {
        WNDCLASSEXW wcex;

        wcex.cbSize = sizeof(WNDCLASSEX);

        wcex.style          = CS_HREDRAW | CS_VREDRAW;
        wcex.lpfnWndProc    = WndProc;
        wcex.cbClsExtra     = 0;
        wcex.cbWndExtra     = 0;
        wcex.hInstance      = hInstance;
        wcex.hIcon          = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_WIN32MESSAGESANDEVENTS));
        wcex.hCursor        = LoadCursor(nullptr, IDC_ARROW);
        wcex.hbrBackground  = (HBRUSH)(COLOR_WINDOW+1);
        wcex.lpszMenuName   = MAKEINTRESOURCEW(IDC_WIN32MESSAGESANDEVENTS);
        wcex.lpszClassName  = szWindowClass;
        wcex.hIconSm        = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL));

        return RegisterClassExW(&wcex);
    }

    //
    //   FUNCTION: InitInstance(HINSTANCE, int)
    //
    //   PURPOSE: Saves instance handle and creates main window
    //
    //   COMMENTS:
    //
    //        In this function, we save the instance handle in a global variable and
    //        create and display the main program window.
    //
    BOOL InitInstance(HINSTANCE hInstance, int nCmdShow)
    {
       hInst = hInstance; // Store instance handle in our global variable

       HWND hWnd = CreateWindowW(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW,
          CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, nullptr, nullptr, hInstance, nullptr);

       if (!hWnd)
       {
          return FALSE;
       }

       ShowWindow(hWnd, nCmdShow);
       UpdateWindow(hWnd);

       return TRUE;
    }

    //
    //  FUNCTION: WndProc(HWND, UINT, WPARAM, LPARAM)
    //
    //  PURPOSE:  Processes messages for the main window.
    //
    //  WM_COMMAND  - process the application menu
    //  WM_PAINT    - Paint the main window
    //  WM_DESTROY  - post a quit message and return
    //
    //
    LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
    {
        switch (message)
        {
        case WM_COMMAND:
            {
                int wmId = LOWORD(wParam);
                // Parse the menu selections:
                switch (wmId)
                {
                case IDM_ABOUT:
                    DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About);
                    break;
                case IDM_EXIT:
                    DestroyWindow(hWnd);
                    break;
                default:
                    return DefWindowProc(hWnd, message, wParam, lParam);
                }
            }
            break;
        case WM_PAINT:
            {
                PAINTSTRUCT ps;
                HDC hdc = BeginPaint(hWnd, &ps);
                // TODO: Add any drawing code that uses hdc here...
                EndPaint(hWnd, &ps);
            }
            break;
        case WM_DESTROY:
            PostQuitMessage(0);
            break;
        default:
            return DefWindowProc(hWnd, message, wParam, lParam);
        }
        return 0;
    }

    // Message handler for about box.
    INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam)
    {
        UNREFERENCED_PARAMETER(lParam);
        switch (message)
        {
        case WM_INITDIALOG:
            return (INT_PTR)TRUE;

        case WM_COMMAND:
            if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL)
            {
                EndDialog(hDlg, LOWORD(wParam));
                return (INT_PTR)TRUE;
            }
            break;
        }
        return (INT_PTR)FALSE;
    }

    /* the added .cpp file */

    #include "stdafx.h"
    #include <afxwin.h>
    class CMainFrame : public CFrameWnd {
    public:
    CMainFrame();
    protected:
    afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);
    DECLARE_MESSAGE_MAP()
    };
    CMainFrame::CMainFrame() {
    // Create the window's frame
    Create(NULL, L"MFC Messages Demo", WS_OVERLAPPEDWINDOW,
    CRect(120, 100, 700, 480), NULL);
    }
    class CMessagesApp : public CWinApp {
    public:
    BOOL InitInstance();
    };
    BEGIN_MESSAGE_MAP(CMainFrame, CFrameWnd)
    ON_WM_CREATE()
    END_MESSAGE_MAP()

    int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct) {
    // Call the base class to create the window
    if (CFrameWnd::OnCreate(lpCreateStruct) == 0) {
    // If the window was successfully created, let the user know
    MessageBox(L"The window has been created!!!");
    // Since the window was successfully created, return 0
    return 0;
    }
    // Otherwise, return -1
    return -1;
    }

    BOOL CMessagesApp::InitInstance() {
    m_pMainWnd = new CMainFrame;
    m_pMainWnd->ShowWindow(SW_SHOW);
    m_pMainWnd->UpdateWindow();
    return TRUE;
    }
    CMessagesApp theApp;


    when i compile the above project, i get this error messages

    Severity Code Description Project File Line Suppression State
    Error (active) #error directive: WINDOWS.H already included.  MFC apps must not #include <windows.h> Win32MessagesandEvents c:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\atlmfc\include\afxv_w32.h 16

    Severity Code Description Project File Line Suppression State
    Error C1189 #error:  WINDOWS.H already included.  MFC apps must not #include <windows.h> Win32MessagesandEvents c:\program files (x86)\microsoft visual studio 14.0\vc\atlmfc\include\afxv_w32.h 16

    i have tried everything i think i can try. can someone be of help

    Sunday, January 29, 2017 1:44 PM

Answers