MFC modeless dialog close immediately

1
votes

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;
}
2
c++winapimfcdialogmodeless
I was having this same issue, and I was even returning TRUE! My problem was that Visual Studio had my default code making my dlg a local variable on the stack, rather than a class member on the heap. When the InitInstance function exited, my stack instance of dlg was deallocated, and I was getting a warning saying the m_pMainWnd member was set to NULL, causing the application to terminate. - Michael Plautz

2 Answers

1
votes

I'm not seeing anything that tells the application to stay alive after opening the modeless window. You need at least one 'modal' style window, or something else to control termination of the application.

1
votes

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.