写如以下代码可以运行，但在打开时出错，问题出在哪？
// p61View.cpp : implementation of the CP61View class
//

#include "stdafx.h"
#include "p61.h"

#include "p61Doc.h"
#include "p61View.h"

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

/////////////////////////////////////////////////////////////////////////////
// CP61View

IMPLEMENT_DYNCREATE(CP61View, CScrollView)

BEGIN_MESSAGE_MAP(CP61View, CScrollView)
    //{{AFX_MSG_MAP(CP61View)
    ON_COMMAND(ID_DRAW_AOTOFIT, OnDrawAotofit)
    ON_COMMAND(ID_DRAW_SOURCESIZE, OnDrawSourcesize)
    ON_COMMAND(ID_DRAW_ZOOMIN, OnDrawZoomin)
    ON_COMMAND(ID_DRAW_ZOOMOUT, OnDrawZoomout)
    ON_WM_ERASEBKGND()
    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()

/////////////////////////////////////////////////////////////////////////////
// CP61View construction/destruction

CP61View::CP61View()
{
    // TODO: add construction code here
    m_bFileOpen=false;
}

CP61View::~CP61View()
{
}

BOOL CP61View::PreCreateWindow(CREATESTRUCT& cs)
{
    // TODO: Modify the Window class or styles here by modifying
    //  the CREATESTRUCT cs

    return CScrollView::PreCreateWindow(cs);
}

/////////////////////////////////////////////////////////////////////////////
// CP61View drawing

void CP61View::OnDraw(CDC* pDC)
{
    CP61Doc* pDoc = GetDocument();
    ASSERT_VALID(pDoc);
    // TODO: add draw code for native data here
    if(!m_bFileOpen)
    {
        return;
    }
    CRect r;
    GetClientRect(&r);
    long scrW,scrH,desW,desH;
    BITMAP BMap;
    bitmap.GetBitmap(&BMap);
    scrW=BMap.bmWidth;
    scrH=BMap.bmHeight;
    switch(m_bZoom)
    {
    case ZOOMFIT:
        desW=r.Width();
        desH=r.Height();
        break;
    case ZOOMSCR:
        desW=scrW;
        desW=scrH;
        break;
    case ZOOMOUT:
        desW=scrW*2;
        desH=scrH*2;
        break;
    case ZOOMIN:
        desW=(long)(scrW/2);
        desH=(long)(scrW/2);
        break;
    }
    CSize sizeTotal;
    sizeTotal.cx=desW;
    sizeTotal.cy=desH;
    SetScrollSizes(MM_TEXT,sizeTotal);
    CDC dcMem;
    dcMem.CreateCompatibleDC(pDC);
    dcMem.SelectObject(&bitmap);
    pDC->StretchBlt(0,0,desW,desH,&dcMem,0,0,scrW,scrH,SRCCOPY);
}

void CP61View::OnInitialUpdate()
{
    CScrollView::OnInitialUpdate();

    CSize sizeTotal;
    // TODO: calculate the total size of this view
    sizeTotal.cx = sizeTotal.cy = 100;
    SetScrollSizes(MM_TEXT, sizeTotal);
}

/////////////////////////////////////////////////////////////////////////////
// CP61View printing

BOOL CP61View::OnPreparePrinting(CPrintInfo* pInfo)
{
    // default preparation
    return DoPreparePrinting(pInfo);
}

void CP61View::OnBeginPrinting(CDC* /*pDC*/, CPrintInfo* /*pInfo*/)
{
    // TODO: add extra initialization before printing
}

void CP61View::OnEndPrinting(CDC* /*pDC*/, CPrintInfo* /*pInfo*/)
{
    // TODO: add cleanup after printing
}

/////////////////////////////////////////////////////////////////////////////
// CP61View diagnostics

#ifdef _DEBUG
void CP61View::AssertValid() const
{
    CScrollView::AssertValid();
}

void CP61View::Dump(CDumpContext& dc) const
{
    CScrollView::Dump(dc);
}

CP61Doc* CP61View::GetDocument() // non-debug version is inline
{
    ASSERT(m_pDocument->IsKindOf(RUNTIME_CLASS(CP61Doc)));
    return (CP61Doc*)m_pDocument;
}
#endif //_DEBUG

/////////////////////////////////////////////////////////////////////////////
// CP61View message handlers

void CP61View::OnDrawAotofit()
{
    // TODO: Add your command handler code here
    m_bZoom=ZOOMFIT;
    Invalidate();
}

void CP61View::OnDrawSourcesize()
{
    // TODO: Add your command handler code here
    m_bZoom=ZOOMSCR;
    Invalidate();
        
}

void CP61View::OnDrawZoomin()
{
    // TODO: Add your command handler code here
    m_bZoom=ZOOMIN;
    Invalidate();
}

void CP61View::OnDrawZoomout()
{
    // TODO: Add your command handler code here
    m_bZoom=ZOOMOUT;
    Invalidate();
}

BOOL CP61View::GetBmp(LPCTSTR lpszSourceName, CBitmap &bitmap)
{
    HBITMAP hbmp=(HBITMAP)::LoadImage(AfxGetInstanceHandle(),lpszSourceName,IMAGE_BITMAP,0,0,LR_LOADFROMFILE);
    if(hbmp==NULL)
        return false;
    bitmap.Detach();
    bitmap.Attach(hbmp);
    return    true;
}

BOOL CP61View::OnEraseBkgnd(CDC* pDC)
{
    // TODO: Add your message handler code here and/or call default
    
    return CScrollView::OnEraseBkgnd(pDC);
}

void CP61View::OnFileOpen()
{
    // TODO: Add your command handler code here
    CString Filepathname;
    CFileDialog dlg(TRUE,_T("BMP"),_T("BMP"),OFN_HIDEREADONLY|OFN_OVERWRITEPROMPT,_T("位图文件()*.BMP|*.BMP|"));
    if(dlg.DoModal())
    {
        Filepathname=dlg.GetPathName();
        if(Filepathname!="*.BMP")
        {
            if(!GetBmp(Filepathname,bitmap))
             MessageBox("打开文件失败","提示",MB_ICONHAND|MB_OK);
            else
            {
                m_bFileOpen=true;
                m_bZoom=ZOOMSCR;
                Invalidate();
            }
        }
    }
}