使用MFC完成手动绘制直线、折线、矩形、圆的代码

以下是使用 MFC 完成手动绘制直线、折线、矩形、圆的代码示例：

1. 在 MFC 应用程序中添加一个继承自 CView 的类 MyView。

2. 在 MyView.h 中添加以下代码：

#pragma once

class MyView : public CView
{
protected:
    CPoint m_ptStart;  // 起始点
    CPoint m_ptEnd;    // 终止点
    int m_nShapeType;  // 形状类型：0-直线，1-折线，2-矩形，3-圆形

public:
    MyView();
    virtual ~MyView();

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 OnPaint();
    DECLARE_MESSAGE_MAP()
};

3. 在 MyView.cpp 中添加以下代码：

#include "stdafx.h"
#include "MyView.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#endif

IMPLEMENT_DYNCREATE(MyView, CView)

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

MyView::MyView()
{
    m_nShapeType = 0;
}

MyView::~MyView()
{
}

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

void MyView::OnMouseMove(UINT nFlags, CPoint point)
{
    if (nFlags & MK_LBUTTON)
    {
        CClientDC dc(this);
        dc.SetROP2(R2_NOTXORPEN);
        dc.SelectStockObject(NULL_BRUSH);
        switch (m_nShapeType)
        {
        case 0:
            dc.MoveTo(m_ptStart);
            dc.LineTo(m_ptEnd);
            m_ptEnd = point;
            dc.MoveTo(m_ptStart);
            dc.LineTo(m_ptEnd);
            break;
        case 1:
            dc.Rectangle(m_ptStart.x, m_ptStart.y, m_ptEnd.x, m_ptEnd.y);
            m_ptEnd = point;
            dc.Rectangle(m_ptStart.x, m_ptStart.y, m_ptEnd.x, m_ptEnd.y);
            break;
        case 2:
            dc.Ellipse(m_ptStart.x, m_ptStart.y, m_ptEnd.x, m_ptEnd.y);
            m_ptEnd = point;
            dc.Ellipse(m_ptStart.x, m_ptStart.y, m_ptEnd.x, m_ptEnd.y);
            break;
        case 3:
            dc.MoveTo(m_ptStart);
            dc.LineTo(m_ptEnd);
            m_ptEnd = point;
            dc.MoveTo(m_ptStart);
            dc.LineTo(m_ptEnd);
            break;
        }
    }
}

void MyView::OnLButtonUp(UINT nFlags, CPoint point)
{
    CClientDC dc(this);
    dc.SetROP2(R2_COPYPEN);
    dc.SelectStockObject(NULL_BRUSH);
    switch (m_nShapeType)
    {
    case 0:
        dc.MoveTo(m_ptStart);
        dc.LineTo(m_ptEnd);
        break;
    case 1:
        dc.Rectangle(m_ptStart.x, m_ptStart.y, m_ptEnd.x, m_ptEnd.y);
        break;
    case 2:
        dc.Ellipse(m_ptStart.x, m_ptStart.y, m_ptEnd.x, m_ptEnd.y);
        break;
    case 3:
        dc.Arc(m_ptStart.x, m_ptStart.y, m_ptEnd.x, m_ptEnd.y,
            (m_ptStart.x + m_ptEnd.x) / 2, (m_ptStart.y + m_ptEnd.y) / 2,
            (m_ptStart.x + m_ptEnd.x) / 2, (m_ptStart.y + m_ptEnd.y) / 2);
        break;
    }
    ReleaseCapture();
}

void MyView::OnPaint()
{
    CPaintDC dc(this);
}

4. 在主窗口类中添加以下代码：

BOOL CMainFrame::OnCreateClient(LPCREATESTRUCT /*lpcs*/,
    CCreateContext* pContext)
{
    m_wndSplitter.CreateStatic(this, 1, 2);
    m_wndSplitter.CreateView(0, 0, RUNTIME_CLASS(MyView),
        CSize(0, 0), pContext);
    m_wndSplitter.CreateView(0, 1, RUNTIME_CLASS(CScrollView),
        CSize(0, 0), pContext);

    return TRUE;
}

5. 在菜单资源中添加以下菜单项：

ID_SHAPE_LINE   直线
ID_SHAPE_POLY   折线
ID_SHAPE_RECT   矩形
ID_SHAPE_ELLIP  圆形

6. 在主窗口类中添加以下代码：

BEGIN_MESSAGE_MAP(CMainFrame, CFrameWnd)
    ON_WM_CREATE()
    ON_COMMAND(ID_SHAPE_LINE, OnShapeLine)
    ON_COMMAND(ID_SHAPE_POLY, OnShapePoly)
    ON_COMMAND(ID_SHAPE_RECT, OnShapeRect)
    ON_COMMAND(ID_SHAPE_ELLIP, OnShapeEllip)
END_MESSAGE_MAP()

void CMainFrame::OnShapeLine()
{
    MyView* pView = (MyView*)m_wndSplitter.GetPane(0, 0);
    pView->m_nShapeType = 0;
}

void CMainFrame::OnShapePoly()
{
    MyView* pView = (MyView*)m_wndSplitter.GetPane(0, 0);
    pView->m_nShapeType = 1;
}

void CMainFrame::OnShapeRect()
{
    MyView* pView = (MyView*)m_wndSplitter.GetPane(0, 0);
    pView->m_nShapeType = 2;
}

void CMainFrame::OnShapeEllip()
{
    MyView* pView = (MyView*)m_wndSplitter.GetPane(0, 0);
    pView->m_nShapeType = 3;
}

7. 运行程序，选择菜单中的不同形状，手动绘制图形。

注意：以上代码示例只是演示如何手动绘制不同形状，还需要根据实际需要完善代码。