获取可停靠窗格C++的句柄时遇到问题

我通过 MFC 向导创建了一个基于多文档功能区的 MFC 应用程序。我试图获得m_wndFileView的句柄以更新其视图。我知道有几种方法可以做到这一点，但我不明白为什么我使用的方法不起作用。所以开始

class CMainFrame : public CMDIFrameWndEx
{
    ...
    CFileView         m_wndFileView;
    CPropertiesWnd    m_wndProperties;
    ...
}
class CFileView : public CDockablePane
{
    ...
    protected:
        CViewTree m_wndFileView;
    ...
};
class CPropertiesWnd : public CDockablePane
{
    ...
    protected:
        CMFCPropertyGridCtrl m_wndPropList;
    ...
};

框架是从主应用程序创建的

// create main MDI Frame window
CMainFrame* pMainFrame = new CMainFrame;
if (!pMainFrame || !pMainFrame->LoadFrame(IDR_MAINFRAME))
{
    delete pMainFrame;
    return FALSE;
}
m_pMainWnd = pMainFrame;
// call DragAcceptFiles only if there's a suffix
//  In an MDI app, this should occur immediately after setting m_pMainWnd
// Enable drag/drop open
m_pMainWnd->DragAcceptFiles();
// Parse command line for standard shell commands, DDE, file open
CCommandLineInfo cmdInfo;
ParseCommandLine(cmdInfo);
// Enable DDE Execute open
EnableShellOpen();
RegisterShellFileTypes(TRUE);

// Dispatch commands specified on the command line.  Will return FALSE if
// app was launched with /RegServer, /Register, /Unregserver or /Unregister.
if (!ProcessShellCommand(cmdInfo))
    return FALSE;
// The main window has been initialized, so show and update it
pMainFrame->ShowWindow(m_nCmdShow);
pMainFrame->UpdateWindow();

MainFrm.cpp 创建以下两个窗格：

// Create file view
CString strFileView;
bNameValid = strFileView.LoadString(IDS_FILE_VIEW);
ASSERT(bNameValid);
if (!m_wndFileView.Create(strFileView, this, CRect(0, 0, 200, 200), TRUE, ID_VIEW_FILEVIEW, WS_CHILD | WS_VISIBLE | WS_CLIPSIBLINGS | WS_CLIPCHILDREN | CBRS_LEFT| CBRS_FLOAT_MULTI))
{
    TRACE0("Failed to create File View windown");
    return FALSE; // failed to create
}

// Create properties window
CString strPropertiesWnd;
bNameValid = strPropertiesWnd.LoadString(IDS_PROPERTIES_WND);
ASSERT(bNameValid);
if (!m_wndProperties.Create(strPropertiesWnd, this, CRect(0, 0, 200, 200), TRUE, ID_VIEW_PROPERTIESWND, WS_CHILD | WS_VISIBLE | WS_CLIPSIBLINGS | WS_CLIPCHILDREN | CBRS_RIGHT | CBRS_FLOAT_MULTI))
{
    TRACE0("Failed to create Properties windown");
    return FALSE; // failed to create
}

从主应用程序.cpp，我可以通过

CWnd * pwnd = ((CWnd*)(AfxGetApp()->m_pMainWnd));
CPropertiesWnd * pPropertiesWnd = (CPropertiesWnd*)pwnd->GetDlgItem(ID_VIEW_PROPERTIESWND);
CMFCPropertyGridCtrl * m_wndPropList = (CMFCPropertyGridCtrl *)pPropertiesWnd->GetDlgItem(2);

但由于某种原因，我无法访问文件视图窗格

CWnd * pwnd = ((CWnd*)(AfxGetApp()->m_pMainWnd));
CFileView * pFileViewWnd = (CFileView*)pwnd->GetDlgItem(ID_VIEW_FILEVIEW);
CViewTree * m_wndFileView= (CViewTree*)pFileViewWnd ->GetDlgItem(4);

（CFileView*）pwnd->GetDlgItem（ID_VIEW_FILEVIEW）; 返回 NULL

请帮忙。这让我发疯。最后，我可以修改m_wndPropList但不能修改m_wndFileView，因为我无法获得 pFileViewWnd 的句柄。以相同方式创建的两个窗格不能以相同的方式访问。为什么？如果需要更多代码，请告诉我。谢谢。