CMemoryDC双缓冲.docx

声明CMemoryDC类的头文件MemoryDC.h如下：#pragma once?#include Afxwin.h??classCMemoryDC?{?public:????? CMemoryDC(CDC *dc, RECT * rect,boolautoRender = false);????? ~CMemoryDC(void);?????? boolIsOK();? ????void Render(CDC * p_objectDC = NULL);????? CDC* GetMemoryDC();????? operator CDC * ();?private:???? boolm_bAutoRender;? CRectm_DCRect;?? CDC* m_pOriginalDC;???? CDC m_MemoryDC;???? CBitmapm_MemoryBmp;};类的实现文件CMemoryDC.cpp如下：#include .MemoryDC.h??CMemoryDC::CMemoryDC(CDC *dc, RECT * rect, boolautoRender)? {???????? m_bAutoRender = autoRender;????? m_pOriginalDC = dc;?? ???if (dc==NULL || rect==NULL)????????? return;????? if (!m_MemoryDC.CreateCompatibleDC(dc))????????? return;????? m_DCRect.SetRect(rect-left, rect-top, rect-right, rect-bottom);??????? if (!m_MemoryBmp.CreateCompatibleBitmap(dc, m_DCRect.Width(), m_DCRect.Height()))????????? return;????? m_MemoryDC.SelectObject(m_MemoryBmp);?}??CMemoryDC::~CMemoryDC(void)? {????? if (m_bAutoRender)????????? Render();????? if (m_MemoryDC.m_hDC!=NULL)????????? m_MemoryDC.DeleteDC();????? if (m_MemoryBmp.m_hObject!=NULL)????????? m_MemoryBmp.DeleteObject();?}??boolCMemoryDC::IsOK()? {????? returnm_MemoryDC.m_hDC!=NULL m_MemoryBmp.m_hObject != NULL;??}?voidCMemoryDC::Render(CDC * p_objectDC)? {????? if (!IsOK())????????? return;???? ??CDC * pDC = (p_objectDC==NULL ?m_pOriginalDC : p_objectDC);????? CSize Size = m_MemoryDC.GetViewportExt() ;????? pDC-BitBlt(????????? m_DCRect.left,????????? m_DCRect.top,????????? m_DCRect.Width(),????????? m_DCRect.Height(),????????? m_MemoryDC,????????? 0,0,????????? SRCCOPY);?}?CDC* CMemoryDC::GetMemoryDC()? {????? return m_MemoryDC;?}?CMemoryDC::operator CDC * ()? {????? return m_MemoryDC;}使用这个类可以大大简化内存DC的创建操作。如果我们在窗口消息WM_PAINT的响应函数中使用内存DC，只要用如下这样简便的代码便可实现：?CRectRect;?GetClientRect(Rect);?CPaintDCdc(this); // device context for painting????? CMemoryDCMemDC(dc, Rect, true);????? if (MemDC.IsOK())?????? {????????? // 使用MemDC画窗口?????? }????// MemDC析构时会自动把图像复制到dc，无需其它操作使用CMemoryDC创建内存DC防止窗口闪烁，编程的代码