求助，MFC鼠标绘图的onDraw()函数怎么写

[sigfield]

void CdrawDlgDlg::OnMouseMove(UINT nFlags, CPoint point)
{
	// TODO:
	static CPoint oldPoint;           //上一个点的位置记录
	static bool firstPressed = true;

	CClientDC dc(this);
	
	if(nFlags & MK_LBUTTON)           //鼠标移动时如果左键被按下，则绘图
	{
		if(firstPressed == true)  //鼠标第一次被点下的时候，在原地画个点
		{
			firstPressed = false;
			dc.SetPixel(point, RGB(255, 255, 255));
			oldPoint = point;
		}
		else                      //鼠标不是第一次被点下的时候，当前点和上个点之间连一条线
		{
			dc.MoveTo(oldPoint);
			dc.LineTo(point);
			oldPoint = point;
		}
	}
	else
	{
		firstPressed = true;
	}
	CDialog::OnMouseMove(nFlags, point);
}

上面这段是绘图的代码，完整起见贴上来，其实没什么可说的。

关键是下面的问题：
当窗口部分移出屏幕时，已绘的线会消失——要写onDraw()/onPaint()函数
问题是：如何写？
我的想法是，各点坐标都存到一个队列里，onDraw()的时候一个一个提取，一条线一条线的重画。
但是，感觉很难看，是否有更好的方法？
我的图都画在一个Picture Control控件里，能否直接对控件进行存取操作？

[zyq5945]

建议你看下孙鑫VC视频的11课

// GraphicView.h : interface of the CGraphicView class
//
/////////////////////////////////////////////////////////////////////////////

#if !defined(AFX_GRAPHICVIEW_H__A0E2AC83_7DFB_4989_9276_209F79BAEDC3__INCLUDED_)
#define AFX_GRAPHICVIEW_H__A0E2AC83_7DFB_4989_9276_209F79BAEDC3__INCLUDED_

#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000


class CGraphicView : public CScrollView
{
protected: // create from serialization only
	CGraphicView();
	DECLARE_DYNCREATE(CGraphicView)

// Attributes
public:
	CGraphicDoc* GetDocument();

// Operations
public:

// Overrides
	// ClassWizard generated virtual function overrides
	//{{AFX_VIRTUAL(CGraphicView)
	public:
	virtual void OnDraw(CDC* pDC);  // overridden to draw this view
	virtual BOOL PreCreateWindow(CREATESTRUCT& cs);
	virtual void OnInitialUpdate();
	protected:
	virtual BOOL OnPreparePrinting(CPrintInfo* pInfo);
	virtual void OnBeginPrinting(CDC* pDC, CPrintInfo* pInfo);
	virtual void OnEndPrinting(CDC* pDC, CPrintInfo* pInfo);
	//}}AFX_VIRTUAL

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

protected:

// Generated message map functions
protected:
	//{{AFX_MSG(CGraphicView)
	afx_msg void OnDot();
	afx_msg void OnLine();
	afx_msg void OnRectangle();
	afx_msg void OnEllipse();
	afx_msg void OnLButtonDown(UINT nFlags, CPoint point);
	afx_msg void OnLButtonUp(UINT nFlags, CPoint point);
	afx_msg void OnPaint();
	afx_msg void OnFileSave();
	afx_msg void OnFileOpen();
	//}}AFX_MSG
	DECLARE_MESSAGE_MAP()
private:
	CDC m_dcCompatible;
	CMetaFileDC m_dcMetaFile;
	CPtrArray m_ptrArray;
	CPoint m_ptOrigin;
	UINT m_nDrawType;
};

#ifndef _DEBUG  // debug version in GraphicView.cpp
inline CGraphicDoc* CGraphicView::GetDocument()
   { return (CGraphicDoc*)m_pDocument; }
#endif

/////////////////////////////////////////////////////////////////////////////

//{{AFX_INSERT_LOCATION}}
// Microsoft Visual C++ will insert additional declarations immediately before the previous line.

#endif // !defined(AFX_GRAPHICVIEW_H__A0E2AC83_7DFB_4989_9276_209F79BAEDC3__INCLUDED_)

// GraphicView.cpp : implementation of the CGraphicView class
//

#include "stdafx.h"
#include "Graphic.h"

#include "GraphicDoc.h"
#include "GraphicView.h"

#include "Graph.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////////////////////////////////////////////////////////////////////
// CGraphicView

IMPLEMENT_DYNCREATE(CGraphicView, CScrollView)

BEGIN_MESSAGE_MAP(CGraphicView, CScrollView)
	//{{AFX_MSG_MAP(CGraphicView)
	ON_COMMAND(IDM_DOT, OnDot)
	ON_COMMAND(IDM_LINE, OnLine)
	ON_COMMAND(IDM_RECTANGLE, OnRectangle)
	ON_COMMAND(IDM_ELLIPSE, OnEllipse)
	ON_WM_LBUTTONDOWN()
	ON_WM_LBUTTONUP()
	ON_WM_PAINT()
	ON_COMMAND(ID_FILE_SAVE, OnFileSave)
	ON_COMMAND(ID_FILE_OPEN, OnFileOpen)
	//}}AFX_MSG_MAP
	// Standard printing commands
	ON_COMMAND(ID_FILE_PRINT, CScrollView::OnFilePrint)
	ON_COMMAND(ID_FILE_PRINT_DIRECT, CScrollView::OnFilePrint)
	ON_COMMAND(ID_FILE_PRINT_PREVIEW, CScrollView::OnFilePrintPreview)
END_MESSAGE_MAP()

/////////////////////////////////////////////////////////////////////////////
// CGraphicView construction/destruction

CGraphicView::CGraphicView()
{
	// TODO: add construction code here
	m_nDrawType=0;
	m_ptOrigin=0;
	m_dcMetaFile.Create();
}

CGraphicView::~CGraphicView()
{
}

BOOL CGraphicView::PreCreateWindow(CREATESTRUCT& cs)
{
	// TODO: Modify the Window class or styles here by modifying
	//  the CREATESTRUCT cs

	return CScrollView::PreCreateWindow(cs);
}

/////////////////////////////////////////////////////////////////////////////
// CGraphicView drawing

void CGraphicView::OnDraw(CDC* pDC)
{
	CGraphicDoc* pDoc = GetDocument();
	ASSERT_VALID(pDoc);
	// TODO: add draw code for native data here
/*	CBrush *pBrush=CBrush::FromHandle((HBRUSH)GetStockObject(NULL_BRUSH));
	pDC->SelectObject(pBrush);

	for(int i=0;i<m_ptrArray.GetSize();i++)
	{
		switch(((CGraph*)m_ptrArray.GetAt(i))->m_nDrawType)
		{
		case 1:
			pDC->SetPixel(((CGraph*)m_ptrArray.GetAt(i))->m_ptEnd,RGB(0,0,0));
			break;
		case 2:
			pDC->MoveTo(((CGraph*)m_ptrArray.GetAt(i))->m_ptOrigin);
			pDC->LineTo(((CGraph*)m_ptrArray.GetAt(i))->m_ptEnd);
			break;
		case 3:
			pDC->Rectangle(CRect(((CGraph*)m_ptrArray.GetAt(i))->m_ptOrigin,
				((CGraph*)m_ptrArray.GetAt(i))->m_ptEnd));
			break;
		case 4:
			pDC->Ellipse(CRect(((CGraph*)m_ptrArray.GetAt(i))->m_ptOrigin,
				((CGraph*)m_ptrArray.GetAt(i))->m_ptEnd));
			break;
		}
	}*/
/*	HMETAFILE hmetaFile;
	hmetaFile=m_dcMetaFile.Close();
	pDC->PlayMetaFile(hmetaFile);
	m_dcMetaFile.Create();
	m_dcMetaFile.PlayMetaFile(hmetaFile);
	DeleteMetaFile(hmetaFile);*/
	CRect rect;
	GetClientRect(&rect);
	pDC->BitBlt(0,0,rect.Width(),rect.Height(),&m_dcCompatible,0,0,SRCCOPY);
}

/////////////////////////////////////////////////////////////////////////////
// CGraphicView printing

BOOL CGraphicView::OnPreparePrinting(CPrintInfo* pInfo)
{
	// default preparation
	return DoPreparePrinting(pInfo);
}

void CGraphicView::OnBeginPrinting(CDC* /*pDC*/, CPrintInfo* /*pInfo*/)
{
	// TODO: add extra initialization before printing
}

void CGraphicView::OnEndPrinting(CDC* /*pDC*/, CPrintInfo* /*pInfo*/)
{
	// TODO: add cleanup after printing
}

/////////////////////////////////////////////////////////////////////////////
// CGraphicView diagnostics

#ifdef _DEBUG
void CGraphicView::AssertValid() const
{
	CScrollView::AssertValid();
}

void CGraphicView::Dump(CDumpContext& dc) const
{
	CScrollView::Dump(dc);
}

CGraphicDoc* CGraphicView::GetDocument() // non-debug version is inline
{
	ASSERT(m_pDocument->IsKindOf(RUNTIME_CLASS(CGraphicDoc)));
	return (CGraphicDoc*)m_pDocument;
}
#endif //_DEBUG

/////////////////////////////////////////////////////////////////////////////
// CGraphicView message handlers

void CGraphicView::OnDot() 
{
	// TODO: Add your command handler code here
	m_nDrawType=1;
}

void CGraphicView::OnLine() 
{
	// TODO: Add your command handler code here
	m_nDrawType=2;
}

void CGraphicView::OnRectangle() 
{
	// TODO: Add your command handler code here
	m_nDrawType=3;
}

void CGraphicView::OnEllipse() 
{
	// TODO: Add your command handler code here
	m_nDrawType=4;
}

void CGraphicView::OnLButtonDown(UINT nFlags, CPoint point) 
{
	// TODO: Add your message handler code here and/or call default
	m_ptOrigin=point;
	CScrollView::OnLButtonDown(nFlags, point);
}

void CGraphicView::OnLButtonUp(UINT nFlags, CPoint point) 
{
	// TODO: Add your message handler code here and/or call default
	CClientDC dc(this);
	CBrush *pBrush=CBrush::FromHandle((HBRUSH)GetStockObject(NULL_BRUSH));
	//dc.SelectObject(pBrush);
	m_dcMetaFile.SelectObject(pBrush);

	if(!m_dcCompatible.m_hDC)
	{
		m_dcCompatible.CreateCompatibleDC(&dc);
		CRect rect;
		GetClientRect(&rect);
		CBitmap bitmap;
		bitmap.CreateCompatibleBitmap(&dc,rect.Width(),rect.Height());
		m_dcCompatible.SelectObject(&bitmap);
		m_dcCompatible.BitBlt(0,0,rect.Width(),rect.Height(),&dc,0,0,SRCCOPY);
		m_dcCompatible.SelectObject(pBrush);
	}
	switch(m_nDrawType)
	{
	case 1:
		//dc.SetPixel(point,RGB(0,0,0));
		//m_dcMetaFile.SetPixel(point,RGB(0,0,0));
		m_dcCompatible.SetPixel(point,RGB(0,0,0));
		break;
	case 2:
		//dc.MoveTo(m_ptOrigin);
		//dc.LineTo(point);
		//m_dcMetaFile.MoveTo(m_ptOrigin);
		//m_dcMetaFile.LineTo(point);
		m_dcCompatible.MoveTo(m_ptOrigin);
		m_dcCompatible.LineTo(point);
		break;
	case 3:
		//dc.Rectangle(CRect(m_ptOrigin,point));
		//m_dcMetaFile.Rectangle(CRect(m_ptOrigin,point));
		m_dcCompatible.Rectangle(CRect(m_ptOrigin,point));
		break;
	case 4:
		//dc.Ellipse(CRect(m_ptOrigin,point));
		//m_dcMetaFile.Ellipse(CRect(m_ptOrigin,point));
		m_dcCompatible.Ellipse(CRect(m_ptOrigin,point));
		break;
	}
	//CGraph graph(m_nDrawType,m_ptOrigin,point);
	//m_ptrArray.Add(&graph);
/*	OnPrepareDC(&dc);
	dc.DPtoLP(&m_ptOrigin);
	dc.DPtoLP(&point);
	CGraph *pGraph=new CGraph(m_nDrawType,m_ptOrigin,point);
	m_ptrArray.Add(pGraph);*/
	CScrollView::OnLButtonUp(nFlags, point);
}

void CGraphicView::OnPaint() 
{
	CPaintDC dc(this); // device context for painting
	
	// TODO: Add your message handler code here
	OnPrepareDC(&dc);
	OnDraw(&dc);
	// Do not call CScrollView::OnPaint() for painting messages
}

void CGraphicView::OnInitialUpdate() 
{
	CScrollView::OnInitialUpdate();
	
	// TODO: Add your specialized code here and/or call the base class
	SetScrollSizes(MM_TEXT,CSize(800,600));
}

void CGraphicView::OnFileSave() 
{
	// TODO: Add your command handler code here
	HMETAFILE hmetaFile;
	hmetaFile=m_dcMetaFile.Close();
	CopyMetaFile(hmetaFile,"meta.wmf");
	m_dcMetaFile.Create();
	DeleteMetaFile(hmetaFile);
}

void CGraphicView::OnFileOpen() 
{
	// TODO: Add your command handler code here
	HMETAFILE hmetaFile;
	hmetaFile=GetMetaFile("meta.wmf");
	m_dcMetaFile.PlayMetaFile(hmetaFile);
	DeleteMetaFile(hmetaFile);
	Invalidate();
}

[loop_k]

你要的答案就是上面那个兄弟贴的代码
要是想实现“橡皮筋”效果
参考http://blog.csdn.net/loop_k/archive/2009/08/24/4480034.aspx

[hhwei1985]

onDraw()/onPaint()是窗口重绘函数,可以解决因为移动覆盖而导致图形消失的问题;
所以
绘图工作要在onDraw()/onPaint()函数中进行,在OnMouseMove里边设置一些变量,
传递到onDraw()/onPaint()里面即可;

[fandh]

onmousemove里面需要画线的数据，保存成视图或者对话框的成员变量，这样，你直接在ondraw或者onpaint里面使用就可以了！

楼主的想法是对的！

[会的越多不会的也就越多]

孙新教程很详细的

[天鹅梦]

一般都是在OnMouseMove中改变某个具有程序分支控制的值，然后在OnDraw函数中根据相应的值进行分支处理

[天下第一好大人]

如果你想实现类似画图板的功能，我有如下建议：

1、折线可以保存在一个链表中（便于添加、删除），每次有点加入或删除就更新链表数据。
2、如果图案所占面积不是特别大(大到无法创建那么大的位图)，可以考虑创建一个内存DC，选入一个CBitmap，每次需要刷新时只要bitblt就行了。
3、MOUSE事件里，添加更新列表以及重画内存DC的代码。

例如：

class CMyClass
{
.............
CDC m_memDC;
CBitmap m_memBMP;
List m_points;
void DrawLine();
}

int CMyClass::OnInitDialog(...)
{
......................
//初始化类的成员，内存DC和CBitmap
CDC* pDC = GetDC();
m_memDC.CreateCompatibleDC(pDC);
m_memBMP.CreateCompatibleBitmap( pDC, 2048, 2048);
m_memDC.SelectObject( &m_memBMP );
.....................
}

void CMyClass::DrawLine()
{
//顺序按链表在内存DC上画图
m_memDC.MoveTo( 第一个点 )
while( m_points没到末尾 ){ m_memDC.LineTo(下一个点); }
Invalidate();
}

void CMyClass::OnMouseMove(UINT nFlags, CPoint point)
{
如果左键处于按下状态，添加新点到链表末尾。
DrawLine();
}

CMyClass::OnPaint()
{
CPaintDC dc(this);
dc.Bitblt(.......m_memDC,..........);
}