Question

I like to write a modeless dialog based app, but I have a problem. When the program starts, the window close immediately.

The same code works fine when I make a modal dialog. (DoModal())

Csetkliens.h

#pragma once

#ifndef __AFXWIN_H__
    #error "include 'stdafx.h' before including this file for PCH"
#endif

#include "resource.h"       // main symbols
#include "CsetkliensDlg.h"

class CCsetkliensApp : public CWinApp
{
public:
    CCsetkliensApp();
    virtual BOOL InitInstance();
    DECLARE_MESSAGE_MAP()

private:
    CCsetkliensDlg* dlg;
};

extern CCsetkliensApp theApp;

Csetkliens.cpp

#include "stdafx.h"
#include "Csetkliens.h"
#include "CsetkliensDlg.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#endif

BEGIN_MESSAGE_MAP(CCsetkliensApp, CWinApp)
    ON_COMMAND(ID_HELP, &CWinApp::OnHelp)
END_MESSAGE_MAP()

CCsetkliensApp::CCsetkliensApp()
{
    dlg = NULL;
}

CCsetkliensApp theApp;

BOOL CCsetkliensApp::InitInstance()
{
    INITCOMMONCONTROLSEX InitCtrls;
    InitCtrls.dwSize = sizeof(InitCtrls);
    InitCtrls.dwICC = ICC_WIN95_CLASSES;
    InitCommonControlsEx(&InitCtrls);

    CWinApp::InitInstance();

    if (!AfxSocketInit())
    {
        AfxMessageBox(IDP_SOCKETS_INIT_FAILED);
        return FALSE;
    }

    CShellManager *pShellManager = new CShellManager;

    dlg = new CCsetkliensDlg();
    m_pMainWnd = dlg;
    dlg->Create(CCsetkliensDlg::IDD);
    dlg->ShowWindow(SW_SHOW);


    if (pShellManager != NULL)
    {
        delete pShellManager;
    }

    return FALSE;
}

CsetkliensDlg.h

#pragma once
#include "ConnectDlg.h"

class CCsetkliensDlg : public CDialogEx
{

public:
    CCsetkliensDlg(CWnd* pParent = NULL);
    enum { IDD = IDD_CSETKLIENS_DIALOG };
protected:
    virtual BOOL OnInitDialog();
    DECLARE_MESSAGE_MAP()
};

CsetkliensDlg.cpp

#include "stdafx.h"
#include "Csetkliens.h"
#include "CsetkliensDlg.h"
#include "afxdialogex.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#endif

CCsetkliensDlg::CCsetkliensDlg(CWnd* pParent /*=NULL*/)
    : CDialogEx(CCsetkliensDlg::IDD, pParent)
{
}

BEGIN_MESSAGE_MAP(CCsetkliensDlg, CDialogEx)
    ON_WM_PAINT()
    ON_WM_QUERYDRAGICON()
END_MESSAGE_MAP()

BOOL CCsetkliensDlg::OnInitDialog()
{
    CDialogEx::OnInitDialog();
    return TRUE;
}

Answer 1

Returning FALSE from your application class’s InitInstance method tells MFC that initialization failed and the application should terminate.

Change that like to return TRUE; and everything should work fine.

BOOL CCsetkliensApp::InitInstance()
{
    INITCOMMONCONTROLSEX InitCtrls;
    InitCtrls.dwSize = sizeof(InitCtrls);
    InitCtrls.dwICC = ICC_WIN95_CLASSES;
    InitCommonControlsEx(&InitCtrls);

    CWinApp::InitInstance();

    if (!AfxSocketInit())
    {
        AfxMessageBox(IDP_SOCKETS_INIT_FAILED);
        return FALSE;
    }

    CShellManager *pShellManager = new CShellManager;

    dlg = new CCsetkliensDlg();
    m_pMainWnd = dlg;
    dlg->Create(CCsetkliensDlg::IDD);
    dlg->ShowWindow(SW_SHOW); // this is not a blocking call!


    if (pShellManager != NULL)
    {
        delete pShellManager;
    }

    return TRUE; // change this one!
}

The reason that it works with a modal dialog (shown by calling the DoModal method) is because a modal dialog creates its own message loop, which runs until you close the dialog. That means that execution effectively “blocks” at the DoModal call without returning control to your InitInstance method, so it doesn’t return FALSE and MFC doesn’t quit. At least not until you close the dialog, in which case you want it to quit, so everything appears the work.