How to create a c++ class that can send and receive window message in MFC - c++

Question

I just want to create a C++ class which can send and process window messages in MFC.
I had tried many ways that I obtained from the internet, roughly like this:
create class myClass::public CWnd using the class Wizard from visual studio 2019 community version.
Use the following code in constructor
CString wcn = ::AfxRegisterWndClass(NULL);
BOOL created = this->CreateEx(0, wcn, _T("YourExcellentWindowClass"), 0, { 0, 0, 0, 0 }, this->GetParent(), /*HWND_MESSAGE,*/ 0, 0);
Setup Message map
BEGIN_MESSAGE_MAP(myClass, CWnd)
ON_MESSAGE(WM_USER + 1, DoNOOP)
END_MESSAGE_MAP()
write message process function:
afx_msg LRESULT myClass::DoNOOP(WPARAM wParam, LPARAM lParam)
{
AfxMessageBox(_T("Get Reaaady for a Ruuummmmmmmbllllle!"));
return LRESULT(true);
}
Sent in message from parent window:
myClass* hmw = new myClass();
::SendMessage(hmw->m_hWnd, WM_USER + 1, 0, 0);
It passed Build process. However, when I run it in debugging mode, SendMessge triggered a Breakpoint in here:
_AFXWIN_INLINE CWnd* CWnd::GetParent() const
{ ASSERT(::IsWindow(m_hWnd)); return CWnd::FromHandle(::GetParent(m_hWnd)); }
which is in afxwin2.inl
I really don't know what to do now.
Please help. I will really appreciate it.
The complete class declaration:
#pragma once
class CMyMessageOnlyWindowClass : public CWnd
{
DECLARE_DYNAMIC(CMyMessageOnlyWindowClass)
public:
CMyMessageOnlyWindowClass();
virtual ~CMyMessageOnlyWindowClass();
protected:
DECLARE_MESSAGE_MAP()
afx_msg LRESULT DoNOOP(WPARAM wParam, LPARAM lParam);
};
Implementation:
#include "pch.h"
#include "MFCmsg.h"
#include "CMyMessageOnlyWindowClass.h"
// CMyMessageOnlyWindowClass
IMPLEMENT_DYNAMIC(CMyMessageOnlyWindowClass, CWnd)
CMyMessageOnlyWindowClass::CMyMessageOnlyWindowClass()
{
CString wcn = ::AfxRegisterWndClass(NULL);
BOOL created = this->CreateEx(0, wcn, _T("YourExcellentWindowClass"), 0, { 0, 0, 0, 0 }, this->GetParent(), /*HWND_MESSAGE,*/ 0, 0);
}
CMyMessageOnlyWindowClass::~CMyMessageOnlyWindowClass()
{
}
BEGIN_MESSAGE_MAP(CMyMessageOnlyWindowClass, CWnd)
ON_MESSAGE(WM_USER + 1, DoNOOP)
END_MESSAGE_MAP()
// CMyMessageOnlyWindowClass message handlers
afx_msg LRESULT CMyMessageOnlyWindowClass::DoNOOP(WPARAM wParam, LPARAM lParam)
{
AfxMessageBox(_T("Get Reaaady for a Ruuummmmmmmbllllle!"));
return LRESULT(true);
}
The main Window is a dialog with only OK and Cancel button.
When click on OK,
void CMFCmsgDlg::OnBnClickedOk()
{
CMyMessageOnlyWindowClass* hmw = new CMyMessageOnlyWindowClass();
hmw->SendMessage(WM_USER + 1);
CDialogEx::OnOK();
}
and this will trigger a breakpoint. Please help.