failure to install a button message handler - c++

Question

I've been trying to write a frame-based MFC application containing a button with simple response to clicks. Unfortunately, it appears like the button does not react to my actions. Here is the application's code:
1) OS.cpp:
#include "stdafx.h"
#include "mfc_includes.h" // some general includes like afxwin.h
#include "OS.h"
#include "MainFrm.h"
#include "button.h"
#ifdef _DEBUG
#define new DEBUG_NEW
#endif
BEGIN_MESSAGE_MAP(COSApp, CWinApp)
END_MESSAGE_MAP()
COSApp::COSApp() {}
COSApp theApp;
btnHelloWorld_t my_button;
BOOL COSApp::InitInstance()
{
INITCOMMONCONTROLSEX InitCtrls;
InitCtrls.dwSize = sizeof(InitCtrls);
InitCtrls.dwICC = ICC_WIN95_CLASSES;
InitCommonControlsEx(&InitCtrls);
CWinApp::InitInstance();
CMainFrame* pFrame = new CMainFrame;
if (!pFrame)
return FALSE;
m_pMainWnd = pFrame;
pFrame->Create(L"", L"The application", WS_OVERLAPPEDWINDOW, CRect(100, 100, 500, 500));
my_button.Create(L"Hello World!", WS_CHILD | WS_VISIBLE | BS_PUSHBUTTON, CRect(30, 30, 150, 80), pFrame, btnHelloWorld_t::GetID());
HFONT font = CreateFont(20, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, L"Times New Roman");
SendMessage(my_button.m_hWnd, WM_SETFONT, (WPARAM)font, true);
pFrame->ShowWindow(SW_SHOW);
pFrame->UpdateWindow();
return TRUE;
}
2) OS.h:
class COSApp : public CWinApp
{
public:
virtual BOOL InitInstance();
afx_msg void OnAppAbout();
DECLARE_MESSAGE_MAP()
};
extern COSApp theApp;
3) button.h (containing a custom button class):
#pragma once
#include "mfc_includes.h"
class btnHelloWorld_t : public CButton
{
static const int is_button = 0x200;
static int id;
public:
btnHelloWorld_t()
{
id++;
};
static const int GetID()
{
return id;
};
afx_msg void Click();
DECLARE_MESSAGE_MAP()
};
int btnHelloWorld_t::id = 0x200;
afx_msg void btnHelloWorld_t::Click()
{
SetWindowText(L"Hello!");
}
BEGIN_MESSAGE_MAP(btnHelloWorld_t, CButton)
ON_BN_CLICKED(btnHelloWorld_t::GetID(), &btnHelloWorld_t::Click)
END_MESSAGE_MAP()
Could you tell me what's wrong and how to make the button to change its text after a click? Thanks in advance.

Answer 1

Your btnHelloWorld_t::GetID() is static method!! When you create the first button, GetID() return 201. Then when the message map is called, GetID() return 202. Then if the message map is called again, GetID() return 203. Then 204, 205....
You have to handle BN_CLICKED command in CMainFrame, not btnHelloWorld_t! If the button is clicked, its parent window will get a WM_COMMAND message, with notifyCode == BN_CLICKED and controlID == the ID you passed to CButton::Create().