帮忙看下这个类多次调用是否有问题
class CMemDCEx : public CDC
{
public:
CMemDCEx(CDC* pDC, const CRect* pRect = NULL, BOOL transparent = FALSE)
{
ASSERT(pDC != NULL);
m_pDC = pDC;
m_pOldBitmap = NULL;
m_bMemDC = !pDC->IsPrinting();
// get the rectangle to draw
if (pRect == NULL)
{
pDC->GetClipBox(&m_rect);
}
else
{
m_rect = *pRect;
}
BOOL bRight = TRUE;
if (m_bMemDC)
{
// create a memory DC
CreateCompatibleDC(pDC);
pDC->LPtoDP(&m_rect);
bRight = m_bitmap.CreateCompatibleBitmap(pDC, m_rect.Width(), m_rect.Height());
if (bRight)
{
m_pOldBitmap = SelectObject(&m_bitmap);
SetMapMode(pDC->GetMapMode());
pDC->DPtoLP(&m_rect);
SetWindowOrg(m_rect.left, m_rect.top);
}
else
{
int iCount = 0;
}
}
else
{
// make a copy of the relevent parts of the current DC for printing
m_bPrinting = pDC->m_bPrinting;
m_hDC = pDC->m_hDC;
m_hAttribDC = pDC->m_hAttribDC;
}
SetBkMode(TRANSPARENT);
// fill background
if (transparent)
{
BitBlt(m_rect.left, m_rect.top, m_rect.Width(), m_rect.Height(), m_pDC, 0, 0, SRCCOPY);
}
else
{
FillSolidRect(m_rect, pDC->GetBkColor()); // not needed in OPAQUE mode?
}
}
~CMemDCEx()
{
if (m_bMemDC)
{
// copy the offscreen bitmap onto the screen
m_pDC->BitBlt(m_rect.left, m_rect.top, m_rect.Width(), m_rect.Height(),
this, m_rect.left, m_rect.top, SRCCOPY);
// swap back the original bitmap
SelectObject(m_pOldBitmap);
}
else
{
// all we need to do is replace the DC with an illegal value, this keeps us from accidently
// deleting the handles associated with the CDC that was passed to the constructor
m_hDC = m_hAttribDC = NULL;
}
}
private:
CBitmap m_bitmap; // offscreen bitmap
CBitmap* m_pOldBitmap; // bitmap originally found in CMemDCEx
CDC* m_pDC; // saves CDC passed in constructor
CRect m_rect; // rectangle of drawing area
BOOL m_bMemDC; // TRUE if CDC really is a Memory DC
};
[解决办法]
怎样多次调用？
如果需要多次绘图，把方法从构造函数和析构函数中提取出来，弄成成员函数
[解决办法]
我也有个：
#if !defined(AFX_MEMDC_H__CA1D3541_7235_11D1_ABBA_00A0243D1382__INCLUDED_)#define AFX_MEMDC_H__CA1D3541_7235_11D1_ABBA_00A0243D1382__INCLUDED_#if _MSC_VER >= 1000#pragma once#endif // _MSC_VER >= 1000// MemDC.h : header file////////////////////////////////////////////////////// CMemDC - memory DC//// Author: Keith Rule// Email: keithr@europa.com// Copyright 1996-1997, Keith Rule//// You may freely use or modify this code provided this// Copyright is included in all derived versions.//// History - 10/3/97 Fixed scrolling bug.// Added print support.// 25 feb 98 - fixed minor assertion bug//// This class implements a memory Device Contextclass CMemDC : public CDC{public: // constructor sets up the memory DC CMemDC(CDC* pDC) : CDC() { ASSERT(pDC != NULL); m_pDC = pDC; m_pOldBitmap = NULL;#ifndef _WIN32_WCE_NO_PRINTING m_bMemDC = !pDC->IsPrinting();#else m_bMemDC = FALSE;#endif if (m_bMemDC) // Create a Memory DC { pDC->GetClipBox(&m_rect); CreateCompatibleDC(pDC); m_bitmap.CreateCompatibleBitmap(pDC, m_rect.Width(), m_rect.Height()); m_pOldBitmap = SelectObject(&m_bitmap);#ifndef _WIN32_WCE SetWindowOrg(m_rect.left, m_rect.top);#endif // EFW - Bug fix - Fill background in case the user has overridden // WM_ERASEBKGND. We end up with garbage otherwise. // CJM - moved to fix a bug in the fix. FillSolidRect(m_rect, pDC->GetBkColor()); } else // Make a copy of the relevent parts of the current DC for printing {#if !defined(_WIN32_WCE) || ((_WIN32_WCE > 201) && !defined(_WIN32_WCE_NO_PRINTING)) m_bPrinting = pDC->m_bPrinting;#endif m_hDC = pDC->m_hDC; m_hAttribDC = pDC->m_hAttribDC; } } // Destructor copies the contents of the mem DC to the original DC ~CMemDC() { if (m_bMemDC) { // Copy the offscreen bitmap onto the screen. m_pDC->BitBlt(m_rect.left, m_rect.top, m_rect.Width(), m_rect.Height(), this, m_rect.left, m_rect.top, SRCCOPY); //Swap back the original bitmap. SelectObject(m_pOldBitmap); } else { // All we need to do is replace the DC with an illegal value, // this keeps us from accidently deleting the handles associated with // the CDC that was passed to the constructor. m_hDC = m_hAttribDC = NULL; } } // Allow usage as a pointer CMemDC* operator->() {return this;} // Allow usage as a pointer operator CMemDC*() {return this;}private: CBitmap m_bitmap; // Offscreen bitmap CBitmap* m_pOldBitmap; // bitmap originally found in CMemDC CDC* m_pDC; // Saves CDC passed in constructor CRect m_rect; // Rectangle of drawing area. BOOL m_bMemDC; // TRUE if CDC really is a Memory DC.};///////////////////////////////////////////////////////////////////////////////{{AFX_INSERT_LOCATION}}// Microsoft Developer Studio will insert additional declarations immediately before the previous line.#endif // !defined(AFX_MEMDC_H__CA1D3541_7235_11D1_ABBA_00A0243D1382__INCLUDED_)
[解决办法]
和你多次调用没关系吧
[解决办法]
有严重的内存泄漏吧
1.DeleteObject的使用
2.注意ReleaseDC和DeleteDC的使用