在MFC中用c++设计一个简单画图程序。要求能擦出所画的内容。并给出详细代码。并且有具体操作步骤。可以让一个新手简单操作成功

以下是一个简单的 MFC 画图程序，支持绘制直线、矩形、椭圆和自由曲线，并且支持擦除功能。

1. 创建一个 MFC 应用程序，命名为 "MyPaint"。

2. 在 "MyPaintView.h" 文件中添加如下代码：

class CMyPaintView : public CView
{
protected: // 仅从序列化创建
    CMyPaintView() noexcept;
    DECLARE_DYNCREATE(CMyPaintView)

// 特性
public:
    CMyPaintDoc* GetDocument() const;

// 操作
public:

// 重写
public:
    virtual void OnDraw(CDC* pDC);  // 重写以绘制该视图
    virtual BOOL PreCreateWindow(CREATESTRUCT& cs);
protected:

// 实现
public:
    virtual ~CMyPaintView();
#ifdef _DEBUG
    virtual void AssertValid() const;
    virtual void Dump(CDumpContext& dc) const;
#endif

protected:
    BOOL m_bDrawing;
    CPoint m_ptOrigin;
    CPoint m_ptPrev;
    int m_nShapeType;
    CObArray m_shapeList;
    int m_nLineWidth;
    COLORREF m_crLineColor;
    BOOL m_bEraser;

protected:
    afx_msg void OnLButtonDown(UINT nFlags, CPoint point);
    afx_msg void OnMouseMove(UINT nFlags, CPoint point);
    afx_msg void OnLButtonUp(UINT nFlags, CPoint point);
    afx_msg void OnLine();
    afx_msg void OnRect();
    afx_msg void OnEllipse();
    afx_msg void OnFree();
    afx_msg void OnLineWidth();
    afx_msg void OnLineColor();
    afx_msg void OnEraser();
    afx_msg void OnUpdateLine(CCmdUI* pCmdUI);
    afx_msg void OnUpdateRect(CCmdUI* pCmdUI);
    afx_msg void OnUpdateEllipse(CCmdUI* pCmdUI);
    afx_msg void OnUpdateFree(CCmdUI* pCmdUI);
    afx_msg void OnUpdateLineWidth(CCmdUI* pCmdUI);
    afx_msg void OnUpdateLineColor(CCmdUI* pCmdUI);
    afx_msg void OnUpdateEraser(CCmdUI* pCmdUI);
    DECLARE_MESSAGE_MAP()
};

3. 在 "MyPaintView.cpp" 文件中添加如下代码：

IMPLEMENT_DYNCREATE(CMyPaintView, CView)

BEGIN_MESSAGE_MAP(CMyPaintView, CView)
    ON_WM_LBUTTONDOWN()
    ON_WM_MOUSEMOVE()
    ON_WM_LBUTTONUP()
    ON_COMMAND(ID_SHAPE_LINE, &CMyPaintView::OnLine)
    ON_COMMAND(ID_SHAPE_RECT, &CMyPaintView::OnRect)
    ON_COMMAND(ID_SHAPE_ELLIPSE, &CMyPaintView::OnEllipse)
    ON_COMMAND(ID_SHAPE_FREE, &CMyPaintView::OnFree)
    ON_COMMAND(ID_LINE_WIDTH, &CMyPaintView::OnLineWidth)
    ON_COMMAND(ID_LINE_COLOR, &CMyPaintView::OnLineColor)
    ON_COMMAND(ID_ERASER, &CMyPaintView::OnEraser)
    ON_UPDATE_COMMAND_UI(ID_SHAPE_LINE, &CMyPaintView::OnUpdateLine)
    ON_UPDATE_COMMAND_UI(ID_SHAPE_RECT, &CMyPaintView::OnUpdateRect)
    ON_UPDATE_COMMAND_UI(ID_SHAPE_ELLIPSE, &CMyPaintView::OnUpdateEllipse)
    ON_UPDATE_COMMAND_UI(ID_SHAPE_FREE, &CMyPaintView::OnUpdateFree)
    ON_UPDATE_COMMAND_UI(ID_LINE_WIDTH, &CMyPaintView::OnUpdateLineWidth)
    ON_UPDATE_COMMAND_UI(ID_LINE_COLOR, &CMyPaintView::OnUpdateLineColor)
    ON_UPDATE_COMMAND_UI(ID_ERASER, &CMyPaintView::OnUpdateEraser)
END_MESSAGE_MAP()

CMyPaintView::CMyPaintView() noexcept
{
    m_bDrawing = FALSE;
    m_ptOrigin = CPoint(0, 0);
    m_ptPrev = CPoint(0, 0);
    m_nShapeType = SHAPE_LINE;
    m_nLineWidth = 1;
    m_crLineColor = RGB(0, 0, 0);
    m_bEraser = FALSE;
}

CMyPaintView::~CMyPaintView()
{
}

BOOL CMyPaintView::PreCreateWindow(CREATESTRUCT& cs)
{
    return CView::PreCreateWindow(cs);
}

void CMyPaintView::OnDraw(CDC* pDC)
{
    CMyPaintDoc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);
    if (!pDoc)
        return;

    for (int i = 0; i < m_shapeList.GetSize(); i++)
    {
        CShape* pShape = (CShape*)m_shapeList.GetAt(i);
        pShape->Draw(pDC);
    }
}

#ifdef _DEBUG
void CMyPaintView::AssertValid() const
{
    CView::AssertValid();
}

void CMyPaintView::Dump(CDumpContext& dc) const
{
    CView::Dump(dc);
}

CMyPaintDoc* CMyPaintView::GetDocument() const // 非调试版本是内联的
{
    ASSERT(m_pDocument->IsKindOf(RUNTIME_CLASS(CMyPaintDoc)));
    return (CMyPaintDoc*)m_pDocument;
}
#endif //_DEBUG

void CMyPaintView::OnLButtonDown(UINT nFlags, CPoint point)
{
    m_bDrawing = TRUE;
    m_ptOrigin = point;
    m_ptPrev = point;
    CClientDC dc(this);

    if (m_bEraser)
    {
        dc.PatBlt(point.x - 10, point.y - 10, 20, 20, WHITENESS);
        SetCapture();
    }
}

void CMyPaintView::OnMouseMove(UINT nFlags, CPoint point)
{
    if (!m_bDrawing)
        return;

    CClientDC dc(this);
    CPen pen(m_bEraser ? PS_SOLID : PS_DOT, m_nLineWidth, m_bEraser ? RGB(255, 255, 255) : m_crLineColor);
    CPen* pOldPen = dc.SelectObject(&pen);
    dc.SetROP2(R2_NOTXORPEN);

    switch (m_nShapeType)
    {
    case SHAPE_LINE:
        dc.MoveTo(m_ptOrigin);
        dc.LineTo(m_ptPrev);
        dc.MoveTo(m_ptOrigin);
        dc.LineTo(point);
        m_ptPrev = point;
        break;

    case SHAPE_RECT:
        dc.Rectangle(m_ptOrigin.x, m_ptOrigin.y, m_ptPrev.x, m_ptPrev.y);
        dc.Rectangle(m_ptOrigin.x, m_ptOrigin.y, point.x, point.y);
        m_ptPrev = point;
        break;

    case SHAPE_ELLIPSE:
        dc.Ellipse(m_ptOrigin.x, m_ptOrigin.y, m_ptPrev.x, m_ptPrev.y);
        dc.Ellipse(m_ptOrigin.x, m_ptOrigin.y, point.x, point.y);
        m_ptPrev = point;
        break;

    case SHAPE_FREE:
        dc.MoveTo(m_ptPrev);
        dc.LineTo(point);
        m_ptPrev = point;
        break;

    default:
        break;
    }

    dc.SelectObject(pOldPen);
}

void CMyPaintView::OnLButtonUp(UINT nFlags, CPoint point)
{
    if (!m_bDrawing)
        return;

    CClientDC dc(this);
    CPen pen(m_bEraser ? PS_SOLID : PS_DOT, m_nLineWidth, m_bEraser ? RGB(255, 255, 255) : m_crLineColor);
    CPen* pOldPen = dc.SelectObject(&pen);
    dc.SetROP2(R2_COPYPEN);

    switch (m_nShapeType)
    {
    case SHAPE_LINE:
        dc.MoveTo(m_ptOrigin);
        dc.LineTo(m_ptPrev);
        dc.LineTo(point);
        break;

    case SHAPE_RECT:
        dc.Rectangle(m_ptOrigin.x, m_ptOrigin.y, m_ptPrev.x, m_ptPrev.y);
        dc.Rectangle(m_ptOrigin.x, m_ptOrigin.y, point.x, point.y);
        break;

    case SHAPE_ELLIPSE:
        dc.Ellipse(m_ptOrigin.x, m_ptOrigin.y, m_ptPrev.x, m_ptPrev.y);
        dc.Ellipse(m_ptOrigin.x, m_ptOrigin.y, point.x, point.y);
        break;

    case SHAPE_FREE:
        dc.MoveTo(m_ptPrev);
        dc.LineTo(point);
        break;

    default:
        break;
    }

    dc.SelectObject(pOldPen);

    if (m_bEraser)
    {
        ReleaseCapture();
    }
    else
    {
        CShape* pShape = NULL;

        switch (m_nShapeType)
        {
        case SHAPE_LINE:
            pShape = new CLine(m_ptOrigin, point, m_nLineWidth, m_crLineColor);
            break;

        case SHAPE_RECT:
            pShape = new CRectShape(m_ptOrigin, point, m_nLineWidth, m_crLineColor);
            break;

        case SHAPE_ELLIPSE:
            pShape = new CEllipse(m_ptOrigin, point, m_nLineWidth, m_crLineColor);
            break;

        case SHAPE_FREE:
            pShape = new CPolyline(m_ptPrev, point, m_nLineWidth, m_crLineColor);
            break;

        default:
            break;
        }

        if (pShape)
        {
            m_shapeList.Add(pShape);
        }
    }

    m_bDrawing = FALSE;
}

void CMyPaintView::OnLine()
{
    m_nShapeType = SHAPE_LINE;
}

void CMyPaintView::OnRect()
{
    m_nShapeType = SHAPE_RECT;
}

void CMyPaintView::OnEllipse()
{
    m_nShapeType = SHAPE_ELLIPSE;
}

void CMyPaintView::OnFree()
{
    m_nShapeType = SHAPE_FREE;
}

void CMyPaintView::OnLineWidth()
{
    CLineWidthDlg dlg(m_nLineWidth);
    if (dlg.DoModal() == IDOK)
    {
        m_nLineWidth = dlg.GetLineWidth();
    }
}

void CMyPaintView::OnLineColor()
{
    CColorDialog dlg(m_crLineColor);
    if (dlg.DoModal() == IDOK)
    {
        m_crLineColor = dlg.GetColor();
    }
}

void CMyPaintView::OnEraser()
{
    m_bEraser = !m_bEraser;
}

void CMyPaintView::OnUpdateLine(CCmdUI* pCmdUI)
{
    pCmdUI->SetCheck(m_nShapeType == SHAPE_LINE);
}

void CMyPaintView::OnUpdateRect(CCmdUI* pCmdUI)
{
    pCmdUI->SetCheck(m_nShapeType == SHAPE_RECT);
}

void CMyPaintView::OnUpdateEllipse(CCmdUI* pCmdUI)
{
    pCmdUI->SetCheck(m_nShapeType == SHAPE_ELLIPSE);
}

void CMyPaintView::OnUpdateFree(CCmdUI* pCmdUI)
{
    pCmdUI->SetCheck(m_nShapeType == SHAPE_FREE);
}

void CMyPaintView::OnUpdateLineWidth(CCmdUI* pCmdUI)
{
    pCmdUI->Enable(!m_bEraser);
}

void CMyPaintView::OnUpdateLineColor(CCmdUI* pCmdUI)
{
    pCmdUI->Enable(!m_bEraser);
}

void CMyPaintView::OnUpdateEraser(CCmdUI* pCmdUI)
{
    pCmdUI->SetCheck(m_bEraser);
}

4. 在 "MyPaintDoc.h" 文件中添加如下代码：

class CMyPaintDoc : public CDocument
{
protected: // 仅从序列化创建
    CMyPaintDoc() noexcept;
    DECLARE_DYNCREATE(CMyPaintDoc)

// 特性
public:

// 操作
public:

// 重写
public:
    virtual BOOL OnNewDocument();
    virtual void Serialize(CArchive& ar);
#ifdef SHARED_HANDLERS
    virtual void InitializeSearchContent();
    virtual void OnDrawThumbnail(CDC& dc, LPRECT lprcBounds);
#endif // SHARED_HANDLERS

// 实现
public:
    virtual ~CMyPaintDoc();
#ifdef _DEBUG
    virtual void AssertValid() const;
    virtual void Dump(CDumpContext& dc) const;
#endif

protected:

// 生成的消息映射函数
protected:
    DECLARE_MESSAGE_MAP()
};

5. 在 "MyPaintDoc.cpp" 文件中添加如下代码：

IMPLEMENT_DYNCREATE(CMyPaintDoc, CDocument)

BEGIN_MESSAGE_MAP(CMyPaintDoc, CDocument)
END_MESSAGE_MAP()


CMyPaintDoc::CMyPaintDoc() noexcept
{
}

CMyPaintDoc::~CMyPaintDoc()
{
}

BOOL CMyPaintDoc::OnNewDocument()
{
    if (!CDocument::OnNewDocument())
        return FALSE;

    return TRUE;
}

void CMyPaintDoc::Serialize(CArchive& ar)
{
    if (ar.IsStoring())
    {
    }
    else
    {
    }
}

#ifdef SHARED_HANDLERS

// 缩略图的绘制由实现此功能的程序负责。
void CMyPaintDoc::OnDrawThumbnail(CDC& dc, LPRECT lprcBounds)
{
    // 修改此代码以绘制文档数据
    dc.FillSolidRect(lprcBounds, RGB(255, 255, 255));

    CString strText = _T("TODO: implement thumbnail drawing here");
    LOGFONT lf;

    CFont* pOldFont = dc.SelectObject(&theApp.m_fontPrint);

    lf = *theApp.m_fontPrint.GetLogFont();
    lf.lfHeight = -12;
    CFont font;
    font.CreateFontIndirect(&lf);
    CFont* pOldFont2 = dc.SelectObject(&font);

    dc.DrawText(strText, lprcBounds, DT_CENTER | DT_WORDBREAK | DT_NOPREFIX);

    dc.SelectObject(pOldFont);
    dc.SelectObject(pOldFont2);
}

// 搜索处理程序的实现由实现此功能的程序负责。
void CMyPaintDoc::InitializeSearchContent()
{
    CString strSearchContent;
    // 从文档数据设置搜索内容。
    // 以下内容不应包含任何未保存的信息、
    // 临时信息或对话框字段。
    strSearchContent = _T("TODO: implement searchable content in the document");

    SetSearchContent(strSearchContent);
}

void CMyPaintDoc::Dump(CDumpContext& dc) const
{
    CDocument::Dump(dc);
}
#endif //_SHARED_HANDLERS

6. 在 "MyPaint.h" 文件中添加如下代码：

class CMyPaintApp : public CWinApp
{
public:
    CMyPaintApp() noexcept;

// 重写
public:
    virtual BOOL InitInstance();
    virtual int ExitInstance();

// 实现

public:
    afx_msg void OnAppAbout();
    DECLARE_MESSAGE_MAP()

private:
    CFont m_fontPrint;
};

extern CMyPaintApp theApp;

7. 在 "MyPaint.cpp" 文件中添加如下代码：

CMyPaintApp theApp;

BEGIN_MESSAGE_MAP(CMyPaintApp, CWinApp)
    ON_COMMAND(ID_APP_ABOUT, &CMyPaintApp::OnAppAbout)
END_MESSAGE_MAP()

CMyPaintApp::CMyPaintApp() noexcept
{
}

BOOL CMyPaintApp::InitInstance()
{
    // 初始化 MFC 和打印机并初始化应用程序字体
    if (!AfxOleInit())
    {
        AfxMessageBox(IDP_OLE_INIT_FAILED);
        return FALSE;
    }
    AfxEnableControlContainer();

    // 创建应用程序字体
    LOGFONT lf;
    memset(&lf, 0, sizeof(lf));
    lf.lfHeight = 12;
    lf.lfWeight = FW_NORMAL;
    lf.lfCharSet = DEFAULT_CHARSET;
    lf.lfOutPrecision = OUT_DEFAULT_PRECIS;
    lf.lfClipPrecision = CLIP_DEFAULT_PRECIS;
    lf.lfQuality = DEFAULT_QUALITY;
    lf.lfPitchAndFamily = VARIABLE_PITCH | FF_SWISS;
    _tcscpy_s(lf.lfFaceName, LF_FACESIZE, _T("Arial"));
    m_fontPrint.CreateFontIndirect(&lf);

    // 初始化标准文档管理器
    // TODO: 可以根据应用程序的特定需要添加一些附加的文档类型。  例如:
    //  CMultiDocTemplate* pDocTemplate;
    //  pDocTemplate = new CMultiDocTemplate(IDR_MyPaintTYPE,
    //    RUNTIME_CLASS(CMyPaintDoc),
    //    RUNTIME_CLASS(CChildFrame), // 自定义 MDI 子框架
    //    RUNTIME_CLASS(CMyPaintView));
    //  if (!pDocTemplate)
    //      return FALSE;
    //  AddDocTemplate(pDocTemplate);

    // 分析标准 SHELL 命令、DDE、打开文件操作
    CCommandLineInfo cmdInfo;
    ParseCommandLine(cmdInfo);

    // 分析标准 shell 命令、DDE、打开文件操作命令行
    if (!ProcessShellCommand(cmdInfo))
        return FALSE;

    // 主窗口已初始化，因此显示它并对其进行更新
    m_pMainWnd->ShowWindow(SW_SHOW);
    m_pMainWnd->UpdateWindow();
    return TRUE;
}

int CMyPaintApp::ExitInstance()
{
    AfxOleTerm(FALSE);

    return CWinApp::ExitInstance();
}

//“关于”菜单命令
void CMyPaintApp::OnAppAbout()
{
    CAboutDlg aboutDlg;
    aboutDlg.DoModal();
}

8. 添加 "MyPaint.rc" 资源文件，并在其中添加菜单、工具栏和对话框资源。

9. 运行程序，即可看到一个简单的画图程序。通过选择不同的绘图形