How to change MFC View by clicking a Button inside the MainFrame - c++

Question

I want to change the presented View by clicking a button inside the Window
like this.
My Project settings:
I made an MFC Project (SDI) without Doc/View support.
I made two more Views in the Designer and added Classes to them. The new View Classes are derived from CFormView. I changed the Constructor and Destructor of the new View Classes to public.
Added them as pointers to MainFrm.h:
CMainView* m_pMainView;
CSecondView* m_pSecondView;
I changed the OnCreate(),OnSetFocus() and OnCmdMsg() Method of MainFrm.cpp like this:
(That allows to present the FormView I made with the Designer)
int CMainFrame::OnCreate(LPCREATESTRUCT lpCreateStruct)
{
if (CFrameWnd::OnCreate(lpCreateStruct) == -1)
return -1;
// First, build the view context structure
CCreateContext ccx;
// Designate the class from which to build the view
ccx.m_pNewViewClass = RUNTIME_CLASS(CMainView);
// Using the structure, create a view
m_pMainView = DYNAMIC_DOWNCAST(CMainView, this->CreateView(&ccx));
if (!m_pMainView)
{
TRACE0("creation of view failed");
}
// Do layout recalc
RecalcLayout();
// Show the view and do an initial update
m_pMainView->ShowWindow(SW_SHOW);
m_pMainView->OnInitialUpdate();
// Set this view active
SetActiveView(m_pMainView);
// Order it to resize the parent window to fit
m_pMainView->ResizeParentToFit(FALSE);
return 0;
}
...
void CMainFrame::OnSetFocus(CWnd* /*pOldWnd*/)
{
m_pMainView->SetFocus();
}
BOOL CMainFrame::OnCmdMsg(UINT nID, int nCode, void* pExtra, AFX_CMDHANDLERINFO* pHandlerInfo)
{
if (m_pMainView->OnCmdMsg(nID, nCode, pExtra, pHandlerInfo))
return TRUE;
return CFrameWnd::OnCmdMsg(nID, nCode, pExtra, pHandlerInfo);
}
Now here comes my problem! I have a button on the First presented View and if you click on it, the view should change. I made the following function with the event handler in the Designer:
void CMainView::OnBnClickedButton1()
{
// What to do here? I want to change the current view to another View by clicking the button
}
If i handle it in the MainFrm.cpp class for example with menue buttons it is no problem... that works fine:
void CMainFrame::OnViewNextview()
{
CCreateContext ccx2;
ccx2.m_pNewViewClass = RUNTIME_CLASS(CSecondView);
m_pSecondView = DYNAMIC_DOWNCAST(CSecondView, this->CreateView(&ccx2));
RecalcLayout();
m_pMainView->ShowWindow(SW_SHOW);
m_pMainView->OnInitialUpdate();
SetActiveView(m_pMainView);
m_pMainView->ResizeParentToFit(FALSE);
}
I tried to write a function in CMainFrame and call this function in CMainView::OnBnClickedButton1() but I don't know how to get the current MainFrm Object. A pointer on MainFrm or a member of it in CMainView did not work.
I searched and red tutorials for days to solve my problem. I also tried it with Doc/View support like shown here:
https://learn.microsoft.com/en-us/cpp/mfc/adding-multiple-views-to-a-single-document?view=vs-2019 but i dont know where to call switchView() correctly.
Maybe anyone can help...

Answer 1

First, you shouldn't really be overriding OnCmdMsg - instead, use DECLARE_MESSAGE_MAP in your header file and BEGIN_MESSAGE_MAP/END_MESSAGE_MAP in your implementation file, and insert handler messages between those two macros.
I see that you already have a handler in your CMainView class for the button click! From here, you should call the CMainFrame function to change to the next view - just as you do when the menu command is given (which you say works). Make that function public and give the MainView class access to a pointer to the main frame (or use AfxGetMainWnd() and cast it to a pointer of your class). Something like this:
void CMainView::OnBnClickedButton1()
{
AfxGetMainWnd()->PostMessage(WM_COMMAND, menuID); // ID of menu command that works!
}

Answer 2

Big hugs for Adrian, i got it to work!
I also added a third view successfully :)
It is very IMPORTANT , to HIDE the last shown Window if you want to implement more views. you can do it like:
void CMainFrame::OnView3()
{
CCreateContext ccx3;
ccx3.m_pNewViewClass = RUNTIME_CLASS(CThirdView);
m_pThirdView = DYNAMIC_DOWNCAST(CThirdView, this->CreateView(&ccx3));
RecalcLayout();
m_pSecondView->ShowWindow(SW_HIDE); // Hide the last Window
m_pThirdView->ShowWindow(SW_SHOW); // Show the new Window
m_pThirdView->OnInitialUpdate();
SetActiveView(m_pThirdView);
//m_pThirdView->ResizeParentToFit(FALSE); //if you call this, the size of the window is the same like in the Designer
}