VCmfc简易画图板代码

以下是一个基于VC++ MFC的简易画图板代码示例：

首先，创建一个MFC应用程序，选择“单文档”类型，然后在资源编辑器中添加一个菜单项“画图板”。

在CMainFrame类中添加以下代码：

#include "MyView.h"

class CMainFrame : public CFrameWnd
{
public:
    CMainFrame();
protected:
    afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);
    afx_msg void OnPaint();
    afx_msg void OnSize(UINT nType, int cx, int cy);
    afx_msg void OnDrawLine();
    afx_msg void OnDrawRectangle();
    afx_msg void OnDrawEllipse();
    DECLARE_MESSAGE_MAP()
private:
    MyView m_wndView;
};

CMainFrame::CMainFrame()
{
    Create(NULL, _T("Drawing Board"), WS_OVERLAPPEDWINDOW, CRect(0, 0, 800, 600));
}

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

    if (!m_wndView.Create(NULL, NULL, AFX_WS_DEFAULT_VIEW, CRect(0, 0, 0, 0), this, AFX_IDW_PANE_FIRST, NULL))
    {
        TRACE0("Failed to create view window\n");
        return -1;
    }

    return 0;
}

void CMainFrame::OnPaint()
{
    CPaintDC dc(this); // device context for painting

    CRect rect;
    GetClientRect(&rect);
    dc.FillSolidRect(&rect, RGB(255, 255, 255));
}

void CMainFrame::OnSize(UINT nType, int cx, int cy)
{
    CFrameWnd::OnSize(nType, cx, cy);

    if (m_wndView.GetSafeHwnd())
        m_wndView.MoveWindow(0, 0, cx, cy);
}

void CMainFrame::OnDrawLine()
{
    m_wndView.SetDrawType(DRAW_LINE);
}

void CMainFrame::OnDrawRectangle()
{
    m_wndView.SetDrawType(DRAW_RECTANGLE);
}

void CMainFrame::OnDrawEllipse()
{
    m_wndView.SetDrawType(DRAW_ELLIPSE);
}

BEGIN_MESSAGE_MAP(CMainFrame, CFrameWnd)
    ON_WM_CREATE()
    ON_WM_PAINT()
    ON_WM_SIZE()
    ON_COMMAND(ID_DRAW_LINE, &CMainFrame::OnDrawLine)
    ON_COMMAND(ID_DRAW_RECTANGLE, &CMainFrame::OnDrawRectangle)
    ON_COMMAND(ID_DRAW_ELLIPSE, &CMainFrame::OnDrawEllipse)
END_MESSAGE_MAP()

在MyView类中添加以下代码：

enum DRAW_TYPE {
    DRAW_NONE = 0,
    DRAW_LINE,
    DRAW_RECTANGLE,
    DRAW_ELLIPSE
};

class MyView : public CView
{
protected:
    MyView();
    DECLARE_DYNCREATE(MyView)

public:
    virtual void OnDraw(CDC* pDC);
    virtual BOOL PreCreateWindow(CREATESTRUCT& cs);
    virtual ~MyView();
    void SetDrawType(DRAW_TYPE type) { m_nDrawType = type; }

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:
    DRAW_TYPE m_nDrawType;
    CPoint m_ptStart;
    CPoint m_ptEnd;
};

MyView::MyView()
{
    m_nDrawType = DRAW_NONE;
}

MyView::~MyView()
{
}

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

void MyView::OnDraw(CDC* pDC)
{
    CDocument* pDoc = GetDocument();
    // TODO: add draw code here
}

void MyView::OnLButtonDown(UINT nFlags, CPoint point)
{
    m_ptStart = point;
    CView::OnLButtonDown(nFlags, point);
}

void MyView::OnMouseMove(UINT nFlags, CPoint point)
{
    if (nFlags & MK_LBUTTON)
    {
        CDC* pDC = GetDC();
        CPen pen;
        pen.CreatePen(PS_SOLID, 2, RGB(0, 0, 0));
        pDC->SelectObject(&pen);
        pDC->SetROP2(R2_NOTXORPEN);

        switch (m_nDrawType)
        {
        case DRAW_LINE:
            pDC->MoveTo(m_ptStart);
            pDC->LineTo(m_ptEnd);
            m_ptEnd = point;
            pDC->MoveTo(m_ptStart);
            pDC->LineTo(m_ptEnd);
            break;

        case DRAW_RECTANGLE:
            pDC->Rectangle(m_ptStart.x, m_ptStart.y, m_ptEnd.x, m_ptEnd.y);
            m_ptEnd = point;
            pDC->Rectangle(m_ptStart.x, m_ptStart.y, m_ptEnd.x, m_ptEnd.y);
            break;

        case DRAW_ELLIPSE:
            pDC->Ellipse(m_ptStart.x, m_ptStart.y, m_ptEnd.x, m_ptEnd.y);
            m_ptEnd = point;
            pDC->Ellipse(m_ptStart.x, m_ptStart.y, m_ptEnd.x, m_ptEnd.y);
            break;

        default:
            break;
        }

        ReleaseDC(pDC);
    }

    CView::OnMouseMove(nFlags, point);
}

void MyView::OnLButtonUp(UINT nFlags, CPoint point)
{
    m_ptEnd = point;

    CView::OnLButtonUp(nFlags, point);
}

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

在资源编辑器中为菜单项添加ID_DRAW_LINE、ID_DRAW_RECTANGLE和ID_DRAW_ELLIPSE命令ID。

最后，在CWinApp类的InitInstance()函数中添加以下代码：

BOOL CMyApp::InitInstance()
{
    CWinApp::InitInstance();

    CMainFrame* pFrame = new CMainFrame;
    m_pMainWnd = pFrame;
    pFrame->LoadFrame(IDR_MAINFRAME, WS_OVERLAPPEDWINDOW | FWS_ADDTOTITLE, NULL, NULL);

    m_pMainWnd->ShowWindow(SW_SHOW);
    m_pMainWnd->UpdateWindow();

    return TRUE;
}

现在，你就可以编译并运行这个简易画图板了，它可以画线、矩形和椭圆。