怎么在对话框中使用双缓冲绘图啊？

双缓冲的意思就是先将图画在内存中，然后再一次拷贝显示到屏幕上，没啥神秘的
画图一般是在OnPaint中画：
CPoint ptCenter;
CRect rect,ellipseRect;
GetClientRect(&rect);
ptCenter = rect.CenterPoint();
CDC dcMem; //用于缓冲作图的内存DC
CBitmap bmp; //内存中承载临时图象的位图
dcMem.CreateCompatibleDC(pDC); //依附窗口DC创建兼容内存DC (就是一个内存DC,所有图形先画在上面)
bmp.CreateCompatibleBitmap(pDC,rect.Width(),rect.Height());//创建兼容位图
dcMem.SelectObject(&bmp); //将位图选择进内存DC
//按原来背景填充客户区，不然会是黑色
dcMem.FillSolidRect(rect,pDC->GetBkColor());
for(int i=20;i>0;i--) //在内存DC上做同样的同心圆图象
{
ellipseRect.SetRect(ptCenter,ptCenter);
ellipseRect.InflateRect(i*10,i*10);
dcMem.Ellipse(ellipseRect);
} pDC->BitBlt(0,0,rect.Width(),rect.Height(),
&dcMem,0,0,SRCCOPY);//将内存DC上的图象拷贝到前台

pDC CDC
在哪里定义啊？怎么定义啊？

大家有没有从对话框里用双缓冲的例子啊？传我一份吧
[email protected]
谢谢大家了

就是bitblt嘛，create一个兼容dc，在上面画图，然后在onpaint里面bitblt到paintdc上。

在onpaint里面画的时候pDC,CDC这些在哪里定义啊？怎么定义？
我是字对话框里面画，没有ondraw啊~

这是我的原程序大家帮我看一看啊，编译是没错可是exe打开就报错
Xv001Dlg.cpp文件// xv001Dlg.h : header file
//#if !defined(AFX_XV001DLG_H__0B7DC168_1268_40FB_B2B2_1786D9C474D1__INCLUDED_)
#define AFX_XV001DLG_H__0B7DC168_1268_40FB_B2B2_1786D9C474D1__INCLUDED_#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000/////////////////////////////////////////////////////////////////////////////
// CXv001Dlg dialogclass CXv001Dlg : public CDialog
{
// Construction
public:
CXv001Dlg(CWnd* pParent = NULL); // standard constructor
CRect rect; // 存储绘图控件的绘图区域 CDC *pDC; // 控件的屏幕绘图设备指针 CDC MemDC; // 内存绘图设备 CBitmap memBitmap; // 用于内存绘图的位图 CBitmap* pOldBmp; // 备份旧的位图指针 CWnd* pWnd; // 绘图控件的指针
// Dialog Data
//{{AFX_DATA(CXv001Dlg)
enum { IDD = IDD_XV001_DIALOG };
// NOTE: the ClassWizard will add data members here
//}}AFX_DATA // ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CXv001Dlg)
protected:
virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support
//}}AFX_VIRTUAL// Implementation
protected:
HICON m_hIcon; // Generated message map functions
//{{AFX_MSG(CXv001Dlg)
virtual BOOL OnInitDialog();
afx_msg void OnSysCommand(UINT nID, LPARAM lParam);
afx_msg void OnPaint();
afx_msg HCURSOR OnQueryDragIcon();
afx_msg void OnTimer(UINT nIDEvent);
afx_msg void OnClose();
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
void DrawWave(CDC *pDC);
};//{{AFX_INSERT_LOCATION}}
// Microsoft Visual C++ will insert additional declarations immediately before the previous line.#endif // !defined(AFX_XV001DLG_H__0B7DC168_1268_40FB_B2B2_1786D9C474D1__INCLUDED_)

Xv001Dlg.cpp文件上面的是.h文件写错了// xv001Dlg.cpp : implementation file
//#include "stdafx.h"
#include "xv001.h"
#include "xv001Dlg.h"#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif/////////////////////////////////////////////////////////////////////////////
// CAboutDlg dialog used for App Aboutclass CAboutDlg : public CDialog
{
public:
CAboutDlg();

// Dialog Data
//{{AFX_DATA(CAboutDlg)
enum { IDD = IDD_ABOUTBOX };
//}}AFX_DATA // ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CAboutDlg)
protected:
virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV support
//}}AFX_VIRTUAL// Implementation
protected:
//{{AFX_MSG(CAboutDlg)
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
};CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
//{{AFX_DATA_INIT(CAboutDlg)
//}}AFX_DATA_INIT
}void CAboutDlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CAboutDlg)
//}}AFX_DATA_MAP
}BEGIN_MESSAGE_MAP(CAboutDlg, CDialog)
//{{AFX_MSG_MAP(CAboutDlg)
// No message handlers
//}}AFX_MSG_MAP
END_MESSAGE_MAP()/////////////////////////////////////////////////////////////////////////////
// CXv001Dlg dialogCXv001Dlg::CXv001Dlg(CWnd* pParent /*=NULL*/)
: CDialog(CXv001Dlg::IDD, pParent)
{
//{{AFX_DATA_INIT(CXv001Dlg)
// NOTE: the ClassWizard will add member initialization here
//}}AFX_DATA_INIT
// Note that LoadIcon does not require a subsequent DestroyIcon in Win32
m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}void CXv001Dlg::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CXv001Dlg)
// NOTE: the ClassWizard will add DDX and DDV calls here
//}}AFX_DATA_MAP
}BEGIN_MESSAGE_MAP(CXv001Dlg, CDialog)
//{{AFX_MSG_MAP(CXv001Dlg)
ON_WM_SYSCOMMAND()
ON_WM_PAINT()
ON_WM_QUERYDRAGICON()
ON_WM_TIMER()
ON_WM_CLOSE()
//}}AFX_MSG_MAP
END_MESSAGE_MAP()/////////////////////////////////////////////////////////////////////////////
// CXv001Dlg message handlersBOOL CXv001Dlg::OnInitDialog()
{
CDialog::OnInitDialog();
    pWnd = GetDlgItem(IDC_COORD); // 获得对话框上的picture的窗口句柄        pWnd->GetClientRect(&rect);         // 获取绘制坐标的文本框pDC = pWnd->GetDC();                 // 获得对话框上的picture的设备指针        pOldBmp = NULL;    // 将旧的位图指针置空        // 创建内存绘图设备，使内存位图的DC与控件的DC关联        memDC.CreateCompatibleDC(pDC);memBitmap.CreateCompatibleBitmap(pDC,rect.right,rect.bottom);        pOldBmp = MemDC.SelectObject(&memBitmap); CDC MemDC; //首先定义一个显示设备对象
CBitmap memBitmap;//定义一个位图对象SetTimer(1,10,NULL);
// Add "About..." menu item to system menu. // IDM_ABOUTBOX must be in the system command range.
ASSERT((IDM_ABOUTBOX & 0xFFF0) == IDM_ABOUTBOX);
ASSERT(IDM_ABOUTBOX < 0xF000); CMenu* pSysMenu = GetSystemMenu(FALSE);
if (pSysMenu != NULL)
{
CString strAboutMenu;
strAboutMenu.LoadString(IDS_ABOUTBOX);
if (!strAboutMenu.IsEmpty())
{
pSysMenu->AppendMenu(MF_SEPARATOR);
pSysMenu->AppendMenu(MF_STRING, IDM_ABOUTBOX, strAboutMenu);
}
} // Set the icon for this dialog.  The framework does this automatically
//  when the application's main window is not a dialog
SetIcon(m_hIcon, TRUE); // Set big icon
SetIcon(m_hIcon, FALSE); // Set small icon

// TODO: Add extra initialization here

return TRUE;  // return TRUE  unless you set the focus to a control
}void CXv001Dlg::OnSysCommand(UINT nID, LPARAM lParam)
{
if ((nID & 0xFFF0) == IDM_ABOUTBOX)
{
CAboutDlg dlgAbout;
dlgAbout.DoModal();
}
else
{
CDialog::OnSysCommand(nID, lParam);
}
}// If you add a minimize button to your dialog, you will need the code below
//  to draw the icon.  For MFC applications using the document/view model,
//  this is automatically done for you by the framework.void CXv001Dlg::OnPaint()
{
pDC->BitBlt(rect.left,rect.top,rect.right,rect.bottom,&MemDC,0,0,SRCCOPY);
if (IsIconic())
{
CPaintDC dc(this); // device context for painting SendMessage(WM_ICONERASEBKGND, (WPARAM) dc.GetSafeHdc(), 0); // Center icon in client rectangle
int cxIcon = GetSystemMetrics(SM_CXICON);
int cyIcon = GetSystemMetrics(SM_CYICON);
CRect rect;
GetClientRect(&rect);
int x = (rect.Width() - cxIcon + 1) / 2;
int y = (rect.Height() - cyIcon + 1) / 2; // Draw the icon
dc.DrawIcon(x, y, m_hIcon);
}
else
{
CDialog::OnPaint();
}
}// The system calls this to obtain the cursor to display while the user drags
//  the minimized window.
HCURSOR CXv001Dlg::OnQueryDragIcon()
{
return (HCURSOR) m_hIcon;
}void CXv001Dlg::DrawWave(CDC *pDC){
//随后建立与屏幕显示兼容的内存显示设备
MemDC.CreateCompatibleDC(NULL);
//这时还不能绘图，因为没有地方画 ^_^
//下面建立一个与屏幕显示兼容的位图，至于位图的大小嘛，可以用窗口的大小，也可以自己定义（如：有滚动条时就要大于当前窗口的大小，在BitBlt时决定拷贝内存的哪部分到屏幕上）
memBitmap.CreateCompatibleBitmap(pDC,100,100);//将位图选入到内存显示设备中
//只有选入了位图的内存显示设备才有地方绘图，画到指定的位图上
CBitmap *pOldBit=MemDC.SelectObject(&memBitmap);
//先用背景色将位图清除干净，这里我用的是白色作为背景
//你也可以用自己应该用的颜色
MemDC.FillSolidRect(0,0,100,100,RGB(255,255,255));
//绘图
MemDC.MoveTo(0,0);
MemDC.LineTo(50,50);//将内存中的图拷贝到屏幕上进行显示
pDC->BitBlt(0,0,100,100,&MemDC,0,0,SRCCOPY);
//绘图完成后的清理
memBitmap.DeleteObject();
MemDC.DeleteDC();
/*CPen pen,*oldpen;            memDC.Rectangle(rect.left,rect.top,rect.right,rect.bottom);         for(int i =0; i<1500; i++)        {                pen.CreatePen(PS_SOLID,1, RGB(rand()%255,rand()%255,rand()%255));                 oldpen = memDC.SelectObject(&pen);                 int x0,y0,x1,y1;                  x0 = rand()%rect.Width();             x1 = rand()%rect.Width();           y0 = rand()%rect.Height();            y1 = rand()%rect.Height();                memDC.MoveTo(x0,y0);            memDC.LineTo(x1,y1);               memDC.SelectObject(oldpen);           pen.DeleteObject();        } */}void CXv001Dlg::OnTimer(UINT nIDEvent)
{
// TODO: Add your message handler code here and/or call default
DrawWave(&MemDC);         // 在位图中画图片         OnPaint();                            // 使屏幕刷新          CDialog::OnTimer(nIDEvent);
}void CXv001Dlg::OnClose()
{
// TODO: Add your message handler code here and/or call default
MemDC.SelectObject(pOldBmp);         MemDC.DeleteDC();         memBitmap.DeleteObject(); CDialog::OnClose();
}

CPaintDC dc(this)；在对话框的ONPaint中这样获取dc

在对话框下，最主要的是找不到ON_WM_ERASEBKGND()消息的映射。所以这个需要手动加入。在.h文件中加入：afx_msg BOOL OnEraseBkgnd(CDC* pDC);在.cpp文件消息映射中加入：    ON_WM_ERASEBKGND()再添上函数：BOOL CPaintPicture::OnEraseBkgnd(CDC* pDC){     return TRUE; }
剩下的绘图工作放在OnPaint()中：CDC dcMem;dcMem.CreateCompatibleDC (&dc);CBitmap MemBitmap;MemBitmap.CreateCompatibleBitmap(&dc,rect.right,rect.bottom);
CBitmap *OldBitmap = dcMem.SelectObject(&MemBitmap);for(int i=0;i<20;i++){       p[i] = CPoint((i*count)*4,i*50);}
COLORREF clrBk1(RGB(255,255,0));CRect rect1(96,36,484,394);CBrush brush(clrBk1);dcMem.FillRect(rect,&brush);
CPen pen3(PS_DASH,2,RGB(255,0,0));dcMem.SelectObject(&pen3);
for(i=0;i<count;i++){              dcMem.MoveTo(p[i]);      dcMem.LineTo(p[i+1]);}dc.BitBlt(0,0,rect.right,rect.bottom,&dcMem,0,0,SRCCOPY);
dcMem.SelectObject(OldBitmap);

调试易

怎么在对话框中使用双缓冲绘图啊？

解决方案 »