How to Replace a View in a CMDIChildWnd Window怎样替换子框架里的视图；

BOOL CFrame::ReplaceView(CRuntimeClass * pViewClass)
{
CCreateContext context;
CView * pCurrentView;
 
// If no active view for the frame, return FALSE because this
// function retrieves the current document from the active view.
//由于这个函数从当前视图里获取文档，如果子框架内没有激活视图，返回FALSE。
if ((pCurrentView=GetActiveView())==NULL)
return FALSE;
 
// If you're already displaying this kind of view, no need to go
// further.如果你显示的视图是目标视图，不需要再处理了
if ((pCurrentView->IsKindOf(pViewClass))==TRUE)
return TRUE;
 
// Get pointer to CDocument object so that it can be used in the
// creation process of the new view.获取文档指针，在创建时使用
CDocument * pDoc= pCurrentView->GetDocument();
 
// Set flag so that document will not be deleted when view is
// destroyed.设置标志防止在视图销毁时，文档会被删除
BOOL bAutoDelete=pDoc->m_bAutoDelete;
pDoc->m_bAutoDelete=FALSE;
// Delete existing view删除当前视图
pCurrentView->DestroyWindow();
// restore flag恢复标志
pDoc->m_bAutoDelete=bAutoDelete;
 
// Create new view and redraw.创建新视图和重绘
context.m_pNewViewClass=pViewClass;
context.m_pCurrentDoc=pDoc;
context.m_pNewDocTemplate=NULL;
context.m_pLastView=NULL;
context.m_pCurrentFrame=this;
 
CView * pNewView = (CView *) pViewClass->CreateObject();
 
if (pNewView == NULL)
{
TRACE1("Warning: Dynamic create of view type %Fs failed\n",
pViewClass->m_lpszClassName);
return FALSE;
}
 
if (!pNewView->Create(NULL, NULL, AFX_WS_DEFAULT_VIEW,
CRect(0,0,0,0), this, AFX_IDW_PANE_FIRST, &context))
{
TRACE0("Warning: couldn't create view for frame\n");
return FALSE; // Programmer can assume FALSE return value
// from this function means that there
// isn't a view.返回FALSE表示没有视图
}
 
// WM_INITIALUPDATE is define in AFXPRIV.H. WM_INITIALUPDATE是在AFXPRIV.H内定义
pNewView->SendMessage(WM_INITIALUPDATE, 0, 0);
 
RecalcLayout();
 
pNewView->UpdateWindow();
 
//设置激活视图为新建视图
SetActiveView(pNewView);
 
return TRUE;
}

The function receives a pointer to CRuntimeClass object for the new view that is desired. It destroys the old view and replaces it with a new view of the same CDocument. When DestroyWindow() is called for the old view, this causes a "delete this" in the CView::PostNcDestroy() function. Also, the CView::~CView destructor calls CView::RemoveView(), which removes the view from the document's view list.
这个函数需要一个指向服务于欲创建视图CRuntimeClass对象的指针。它销毁旧的视图，用新的来替换。当用旧视图调用DestroyWindow()函数，会导致CView::PostNcDestroy()内的"delete this"。同样CView::~CView析构函数会调用CView::RemoveView()，这个函数会把视图从文档的视图列表里删除视图。

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