MFC 双缓冲,该如何解决

MFC 双缓冲
在onPaint里调用DrawBK函数，未能正确显示图片，谢谢

void DrawBMP(HDC hDstDC, CString strPath)

{

	HDC hDC;

	HBITMAP hBmp;

	HBITMAP hOldBmp;

	BITMAP bm;

	hDC = CreateCompatibleDC(NULL);


	hBmp = (HBITMAP)LoadImage(NULL, strPath, IMAGE_BITMAP, 0, 0, LR_DEFAULTSIZE | LR_LOADFROMFILE | LR_CREATEDIBSECTION);


	hOldBmp = (HBITMAP)SelectObject(hDC ,hBmp);


	GetObject(hBmp, sizeof(BITMAP), &bm);


	BitBlt(hDstDC, 0, 0, bm.bmWidth, bm.bmHeight, hDC, 0, 0,SRCCOPY);


	SelectObject(hDC ,hOldBmp);

	DeleteObject(hDC);

	DeleteObject(hBmp);

}


void DrawBK(CPaintDC& dc)

{

	HDC hMemDC;

	HDC hDC;

	hMemDC = CreateCompatibleDC(NULL);

	DrawBMP(hMemDC, L"D:\\1.BMP");


	hDC = dc.GetSafeHdc();


	BitBlt(hDC, 0, 0, 1000, 1000, hMemDC, 0, 0, SRCCOPY);


	DeleteObject(hMemDC);

	// dc.BitBlt(330,30,5000,5000,&MemDC,0,0,SRCCOPY);

}

------解决方案--------------------
都说没有画布了

void DrawBK(CPaintDC& dc)

{	

  HDC hDC = dc.GetSafeHdc();

  int nWidth = dc.GetDeviceCaps(HORZRES);

  int nHeight = dc.GetDeviceCaps(VERTRES);

  

  HDC hMemDC = CreateCompatibleDC(hDC);

  HBITMAP hBitmap = CreateCompatibleBitmap(hDC, nWidth, nHeight);  

  HBITMAP hOldBitamp = (HBITMAP)SelectObject(hMemDC, hBitmap);   

  

  DrawBMP(hMemDC, L"D:\\1.BMP");


  BitBlt(hDC, 0, 0, nWidth, nHeight, hMemDC, 0, 0, SRCCOPY);


  SelectObject(hMemDC, hOldBitamp);  

  DeleteObject(hBitmap);

  DeleteDC(hMemDC);

}