QTableView will not display in a QTabWidget

[CBM]

I am pretty new with Qt, and I am sure for an experienced programmer this problem is more than ridiculous. But I am eager to learn it. Hence, I am most interested to understand why my code is not working.
Thanks to everybody, who brings me into the right direction to solve my problem!

Okay, here is my problem:
In an QApplication I have QTabWidget (NOT QTableWidget!) as a central Widget.
The QTabWidget has three tabs.
The content for each Tab should come from a "selfmade" class derived from QWidget.

For the first tab "ra", it work as desired. But now I am stuck with the second tab "rf". This second tab should show a QTableView. I have marked the relevant parts in the code below with "//PROBLEM".

mainwindow.cpp

#include <QtGui/QMainWindow>
#include <QAction>
#include <QMenuBar>
#include "mainwindow.h"
#include "Reiseangaben/reiseangaben.h"
#include "Reiseabfolge/reiseabfolge.h"
#include "Reisespesen/reisespesen.h"
 
MainWindow::MainWindow() {
 
    setWindowTitle(tr("Alexander's Reisekostenabrechner"));
    resize(400, 200);
    createActions();
    createMenus();
 
    widget_TabCentral = new QTabWidget(this);
    setCentralWidget(widget_TabCentral);
 
    widget_TabCentral->setObjectName(QString::fromUtf8("widget_TabCentral"));
 
    Reiseangaben *ra = new(Reiseangaben);                                       // WORKS WELL
    widget_TabCentral->addTab(ra, "Allgemeine Reiseangaben");
 
    Reiseabfolge *rf = new(Reiseabfolge);                                           // PROBLEM
    widget_TabCentral->addTab(rf, "Reiseabfolge / Tagespauschale");
 
    Reisespesen *sp = new(Reisespesen);
    widget_TabCentral->addTab(sp, "Spesen");
}

#include <QtGui/QMainWindow>
#include <QAction>
#include <QMenuBar>
#include "mainwindow.h"
#include "Reiseangaben/reiseangaben.h"
#include "Reiseabfolge/reiseabfolge.h"
#include "Reisespesen/reisespesen.h"

MainWindow::MainWindow() {

    setWindowTitle(tr("Alexander's Reisekostenabrechner"));
    resize(400, 200);
    createActions();
    createMenus();

    widget_TabCentral = new QTabWidget(this);
    setCentralWidget(widget_TabCentral);

    widget_TabCentral->setObjectName(QString::fromUtf8("widget_TabCentral"));

    Reiseangaben *ra = new(Reiseangaben);                                       // WORKS WELL
    widget_TabCentral->addTab(ra, "Allgemeine Reiseangaben");

    Reiseabfolge *rf = new(Reiseabfolge);                                           // PROBLEM
    widget_TabCentral->addTab(rf, "Reiseabfolge / Tagespauschale");

    Reisespesen *sp = new(Reisespesen);
    widget_TabCentral->addTab(sp, "Spesen");
}

To copy to clipboard, switch view to plain text mode 

To keep it simple for the beginning, I decide just to display in the second (Problem-)Tab rf a QTableView with content about the current directory (QDirModel). I have putted the QTableView into a QGridLayout. I am not sure if this is necessary. I did this to make sure my QTableView is within a widget, since addTab requires a widget as an argument.

reiseabfolge.cpp

#include <QtGui>
#include "reiseabfolge.h"
 
Reiseabfolge::Reiseabfolge() {
 
  QGridLayout *layoutGrid = new QGridLayout(this);
 
  QDirModel dirModel;
 
  QTableView *tav = new QTableView;
  tav->setModel(&dirModel);
  layoutGrid->addWidget(tav, 0, 0);
 
  QModelIndex cwdIndex = dirModel.index(QDir::currentPath());
  tav->setRootIndex(cwdIndex);
}

#include <QtGui>
#include "reiseabfolge.h"

Reiseabfolge::Reiseabfolge() {

  QGridLayout *layoutGrid = new QGridLayout(this);

  QDirModel dirModel;

  QTableView *tav = new QTableView;
  tav->setModel(&dirModel);
  layoutGrid->addWidget(tav, 0, 0);

  QModelIndex cwdIndex = dirModel.index(QDir::currentPath());
  tav->setRootIndex(cwdIndex);
}

To copy to clipboard, switch view to plain text mode 

What is my problem:
The second Tab shows only a white box with noting in it. The white box must be the QGridLayout, but this QGridLayout is empty. It does not show the QTableView .

For completeness, here some further files:
reiseabfolge.h

#ifndef REISEABFOLGE_H
#define REISEABFOLGE_H
 
#include <QtGui/QWidget>
 
class Reiseabfolge : public QWidget {
 
public:
        Reiseabfolge();
};
 
#endif // REISEABFOLGE_H

#ifndef REISEABFOLGE_H
#define REISEABFOLGE_H

#include <QtGui/QWidget>

class Reiseabfolge : public QWidget {

public:
        Reiseabfolge();
};

#endif // REISEABFOLGE_H

To copy to clipboard, switch view to plain text mode 

mainwindow.h:

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
 
class MainWindow : public QMainWindow {
 
    private:
        Q_OBJECT
        QTabWidget *widget_TabCentral;
        void createActions();
        void createMenus();
 
        QMenu *dateiMenu;
        QAction *neueDatei_Action;
        QAction *oeffneDatei_Action;
        QAction *speicherDatei_Action;
        QAction *speicherDateiUnter_Action;
        QAction *beendeProgramm_Action;
 
    public:
        MainWindow();
        ~MainWindow();
 
    private slots:
        void neueDatei();
        void oeffneDatei();
        bool speicherDatei();
        bool speicherDateiUnter();
        bool beendeProgramm();
 
};
 
#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

class MainWindow : public QMainWindow {

    private:
        Q_OBJECT
        QTabWidget *widget_TabCentral;
        void createActions();
        void createMenus();

        QMenu *dateiMenu;
        QAction *neueDatei_Action;
        QAction *oeffneDatei_Action;
        QAction *speicherDatei_Action;
        QAction *speicherDateiUnter_Action;
        QAction *beendeProgramm_Action;

    public:
        MainWindow();
        ~MainWindow();

    private slots:
        void neueDatei();
        void oeffneDatei();
        bool speicherDatei();
        bool speicherDateiUnter();
        bool beendeProgramm();

};

#endif // MAINWINDOW_H

To copy to clipboard, switch view to plain text mode 

Thanks to everybody, who can tell me what I have misunderstood and made wrong.

[wysota]

You are setting a model that is a local variable. When the constructor ends, the object goes out of scope and is destroyed, hence your table view doesn't have a model assigned to it anymore. Create the model on the heap and all will be fine.

[nish]

Qt expects everything to be allocated on heap, at least QObjects