MFC中App,Doc,MainFrame,View各指针的互相获取

首先说明这四个类的

执行顺序是：App->Doc->MainFrame->View

消息响应顺序是：View->Doc->MainFrame->App

// App中获取其它三项指针
void CSDIApp::OnApp()
{
    // App
    // Doc
    CDocument *pDoc = ((CFrameWndEx *)m_pMainWnd)->GetActiveDocument();//成员变量CFrameWndEx m_pMainWnd
    // MainFrame
    CFrameWndEx *pMain = (CFrameWndEx *)AfxGetMainWnd();
    // View
    CView *pView = ((CFrameWndEx *)m_pMainWnd)->GetActiveView();
}

// Doc中获取其它三项指针
CSDIDoc::CSDIDoc()//构造函数
{
    // App
    CWinAppEx *pApp = (CWinAppEx *)AfxGetApp();
    // Doc
    // MainFrame
    // Doc的创建先于MainFrame
    // View
    // Doc的创建先于View
}
void CSDIDoc::OnDoc()
{
    // App
    // 同构造函数
    // Doc
    // MainFrame
    CFrameWndEx *pMain = (CFrameWndEx *)AfxGetMainWnd();
    // View
    CView *pView= (CView *)pMain->GetActiveView();     
    POSITION pos = GetFirstViewPosition();       
    pView = GetNextView(pos); 
}
    
// MainFrame中获取其它三项指针
CMainFrame::CMainFrame()//构造函数
{
    theApp.m_nAppLook = theApp.GetInt(_T("ApplicationLook"), ID_VIEW_APPLOOK_VS_2005);
    // App
    CWinAppEx *pApp = (CWinAppEx *)AfxGetApp();
    // Doc
    // 构造函数里无法得到当前激活的Doc
    // MainFrame
    // View
    // 构造函数里无法得到View指针，因为Main先于View创建。
}
void CMainFrame::OnMain()
{
    // App
    // 同构造函数
    // Doc
    CDocument *pDoc = (CDocument *)GetActiveDocument();
    // MainFrame
    // View
    CView *pView = (CView *)GetActiveView();
}

// View中获取其它三项指针
CSDIView::CSDIView()//构造函数
{
    // App
    CWinAppEx *pApp = (CWinAppEx *)AfxGetApp();
    // Doc
    /* 无法在View的构造函数里得到Doc指针
       GetDocument();实际上是返回m_pDocument
       m_pDocument在OnCreate();里创建        */
    //CDocument *pDoc = GetDocument();
    // MainFrame
    // 构造函数里无法得到MainFrame指针
    // CFrameWndEx *pMain = (CFrameWndEx *)pApp->m_pMainWnd;
    // View
}
void CSDIView::OnView()
{
    // App
    // 同构造函数
    // Doc
    CDocument *pDoc = GetDocument();
    // MainFrame
    CFrameWndEx *pMain = (CFrameWndEx *)AfxGetMainWnd();
    // View
}

// Dlg中获取指针
CDlg::CDlg(CWnd* pParent /*=NULL*/)//构造函数
    : CDialog(CDlg::IDD, pParent)
{
    // App
    CWinAppEx *pApp = (CWinAppEx *)AfxGetApp();
    // Doc
    CDocument *pDoc = ((CFrameWndEx *)AfxGetMainWnd())->GetActiveDocument();
    // MainFrame
    CFrameWndEx *pMain = (CFrameWndEx *)AfxGetMainWnd();
    // View
    CView *pView = ((CFrameWndEx *)AfxGetMainWnd())->GetActiveView();
}