使用MFC完成手动绘制点、手绘线、折线、圆的代码

以下是使用MFC完成手动绘制点、手绘线、折线、圆的代码：

首先在类视图中创建一个新的View类，例如CMyDrawView。

在CMyDrawView.h文件中添加如下代码：

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

// 特性
public:
    CMyDrawDoc* 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 ~CMyDrawView();
#ifdef _DEBUG
    virtual void AssertValid() const;
    virtual void Dump(CDumpContext& dc) const;
#endif

protected:

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

private:
    CPoint m_ptStart;  // 起点
    CPoint m_ptEnd;    // 终点
    BOOL m_bDrawing;   // 是否正在绘制
    int m_nShape;      // 绘制的形状：0-点，1-线，2-折线，3-圆
    CArray<CPoint, CPoint&> m_arrPoints;  // 折线的点集合
};

#ifndef _DEBUG  // MyDrawView.cpp 中的调试版本
inline CMyDrawDoc* CMyDrawView::GetDocument() const
   { return reinterpret_cast<CMyDrawDoc*>(m_pDocument); }
#endif

在CMyDrawView.cpp文件中添加如下代码：

// CMyDrawView

IMPLEMENT_DYNCREATE(CMyDrawView, CView)

BEGIN_MESSAGE_MAP(CMyDrawView, CView)
    ON_WM_LBUTTONDOWN()
    ON_WM_MOUSEMOVE()
    ON_WM_LBUTTONUP()
END_MESSAGE_MAP()

// CMyDrawView 构造/析构

CMyDrawView::CMyDrawView() noexcept
{
    m_bDrawing = FALSE;
    m_nShape = 0;
}

CMyDrawView::~CMyDrawView()
{
}

BOOL CMyDrawView::PreCreateWindow(CREATESTRUCT& cs)
{
    // TODO: 在此处通过修改
    //  CREATESTRUCT cs 来修改窗口类或样式

    return CView::PreCreateWindow(cs);
}

// CMyDrawView 绘制

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

    // 绘制折线
    if (m_nShape == 2)
    {
        if (m_arrPoints.GetSize() > 0)
        {
            POINT* pPoints = new POINT[m_arrPoints.GetSize()];
            for (int i = 0; i < m_arrPoints.GetSize(); i++)
            {
                pPoints[i] = m_arrPoints.GetAt(i);
            }
            pDC->Polyline(pPoints, m_arrPoints.GetSize());
            delete[] pPoints;
        }
    }

    // 绘制圆
    if (m_nShape == 3)
    {
        int nRadius = (int)sqrt((double)((m_ptStart.x - m_ptEnd.x) * (m_ptStart.x - m_ptEnd.x) + (m_ptStart.y - m_ptEnd.y) * (m_ptStart.y - m_ptEnd.y)));
        pDC->Ellipse(m_ptStart.x - nRadius, m_ptStart.y - nRadius, m_ptStart.x + nRadius, m_ptStart.y + nRadius);
    }
}

// CMyDrawView 消息处理程序

void CMyDrawView::OnLButtonDown(UINT nFlags, CPoint point)
{
    m_bDrawing = TRUE;
    m_ptStart = point;
    m_ptEnd = point;

    // 绘制点
    if (m_nShape == 0)
    {
        CDC* pDC = GetDC();
        pDC->SetPixel(m_ptStart, RGB(0, 0, 0));
        ReleaseDC(pDC);
    }

    CView::OnLButtonDown(nFlags, point);
}

void CMyDrawView::OnMouseMove(UINT nFlags, CPoint point)
{
    if (m_bDrawing)
    {
        CDC* pDC = GetDC();
        pDC->SetROP2(R2_NOTXORPEN);

        // 擦除之前的绘制
        if (m_nShape == 1 || m_nShape == 2 || m_nShape == 3)
        {
            pDC->MoveTo(m_ptStart);
            pDC->LineTo(m_ptEnd);
        }

        // 更新终点
        m_ptEnd = point;

        // 绘制线
        if (m_nShape == 1)
        {
            pDC->MoveTo(m_ptStart);
            pDC->LineTo(m_ptEnd);
        }

        // 绘制折线
        if (m_nShape == 2)
        {
            if (m_arrPoints.GetSize() > 0)
            {
                pDC->MoveTo(m_arrPoints.GetAt(m_arrPoints.GetSize() - 1));
                pDC->LineTo(m_ptEnd);
            }
            else
            {
                pDC->MoveTo(m_ptStart);
                pDC->LineTo(m_ptEnd);
            }
        }

        // 绘制圆
        if (m_nShape == 3)
        {
            pDC->Ellipse(m_ptStart.x - abs(m_ptStart.x - m_ptEnd.x), m_ptStart.y - abs(m_ptStart.x - m_ptEnd.x), m_ptStart.x + abs(m_ptStart.x - m_ptEnd.x), m_ptStart.y + abs(m_ptStart.x - m_ptEnd.x));
        }

        pDC->SetROP2(R2_COPYPEN);
        ReleaseDC(pDC);
    }

    CView::OnMouseMove(nFlags, point);
}

void CMyDrawView::OnLButtonUp(UINT nFlags, CPoint point)
{
    m_bDrawing = FALSE;

    // 绘制线
    if (m_nShape == 1)
    {
        CDC* pDC = GetDC();
        pDC->MoveTo(m_ptStart);
        pDC->LineTo(m_ptEnd);
        ReleaseDC(pDC);
    }

    // 绘制折线
    if (m_nShape == 2)
    {
        m_arrPoints.Add(point);
    }

    // 绘制圆
    if (m_nShape == 3)
    {
        Invalidate();
    }

    CView::OnLButtonUp(nFlags, point);
}

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

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

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

接下来在CMyDrawDoc.cpp文件中添加如下代码：

// CMyDrawDoc

IMPLEMENT_DYNCREATE(CMyDrawDoc, CDocument)

BEGIN_MESSAGE_MAP(CMyDrawDoc, CDocument)
END_MESSAGE_MAP()

// CMyDrawDoc 构造/析构

CMyDrawDoc::CMyDrawDoc() noexcept
{
}

CMyDrawDoc::~CMyDrawDoc()
{
}

BOOL CMyDrawDoc::OnNewDocument()
{
    if (!CDocument::OnNewDocument())
        return FALSE;
    return TRUE;
}

// CMyDrawDoc 序列化

void CMyDrawDoc::Serialize(CArchive& ar)
{
    if (ar.IsStoring())
    {
        // TODO: add storing code here
    }
    else
    {
        // TODO: add loading code here
    }
}

#ifdef _DEBUG
void CMyDrawDoc::AssertValid() const
{
    CDocument::AssertValid();
}

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

最后，在MainFrm.cpp文件中添加如下代码：

// CMainFrame

IMPLEMENT_DYNCREATE(CMainFrame, CFrameWnd)

BEGIN_MESSAGE_MAP(CMainFrame, CFrameWnd)
    ON_WM_CREATE()
    ON_COMMAND(ID_DRAW_POINT, OnDrawPoint)
    ON_COMMAND(ID_DRAW_LINE, OnDrawLine)
    ON_COMMAND(ID_DRAW_POLYLINE, OnDrawPolyline)
    ON_COMMAND(ID_DRAW_CIRCLE, OnDrawCircle)
END_MESSAGE_MAP()

// CMainFrame 构造/析构

CMainFrame::CMainFrame() noexcept
{
    // TODO: 在此添加成员初始化代码
}

CMainFrame::~CMainFrame()
{
}

int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
    if (CFrameWnd::OnCreate(lpCreateStruct) == -1)
        return -1;

    // TODO:  如果在此处添加任何特定于应用程序的代码，
    //  将该代码放置于最终应该出现的位置

    return 0;
}

BOOL CMainFrame::PreCreateWindow(CREATESTRUCT& cs)
{
    if( !CFrameWnd::PreCreateWindow(cs) )
        return FALSE;
    // TODO: 在此处通过修改
    //   CREATESTRUCT cs 来修改窗口类或样式

    return TRUE;
}

// CMainFrame 消息处理程序

void CMainFrame::OnDrawPoint()
{
    CMyDrawView* pView = (CMyDrawView*)GetActiveView();
    if (pView != NULL)
    {
        pView->m_nShape = 0;
    }
}

void CMainFrame::OnDrawLine()
{
    CMyDrawView* pView = (CMyDrawView*)GetActiveView();
    if (pView != NULL)
    {
        pView->m_nShape = 1;
    }
}

void CMainFrame::OnDrawPolyline()
{
    CMyDrawView* pView = (CMyDrawView*)GetActiveView();
    if (pView != NULL)
    {
        pView->m_nShape = 2;
        pView->m_arrPoints.RemoveAll();
    }
}

void CMainFrame::OnDrawCircle()
{
    CMyDrawView* pView = (CMyDrawView*)GetActiveView();
    if (pView != NULL)
    {
        pView->m_nShape = 3;
    }
}

现在可以在菜单栏上添加四个按钮，分别对应绘制点、线、折线和圆的功能。当用户选择其中一个按钮时，就改变视图中的m_nShape变量，使之对应相应的绘制形状。当用户开始绘制时，OnLButtonDown()函数将启动绘制过程，并在OnMouseMove()函数中更新绘制结果。当用户完成绘制时，OnLButtonUp()函数将完成绘制。

注意：本示例只支持绘制单个圆形。如果需要绘制多个圆形，可以用一个CArray来存储所有的圆心和半径。