Russian Qt Forum

    Table = new QTableWidget(this);
    hbLayout = new QHBoxLayout(this);

    Table->setColumnCount(4);
    Table->setRowCount(5);
    //Table->setGeometry(20,20,500,300);

    hbLayout = new QHBoxLayout(this);
    hbLayout->addWidget(Table);
    this->setLayout(hbLayout);

#include <QApplication>
#include <QWidget>
#include <QBoxLayout>
#include <QTableWidget>
#include <QHeaderView>

int main(int argc, char** argv) {
    QApplication app(argc, argv);

    QWidget wgt;
    QTableWidget* Table = new QTableWidget(&wgt);
    Table->horizontalHeader()->setResizeMode(QHeaderView::Stretch);
    Table->setColumnCount(4);
    Table->setRowCount(5);
    //Table->setGeometry(20,20,500,300);

    QHBoxLayout* hbLayout = new QHBoxLayout(&wgt);
    hbLayout->addWidget(Table);
    wgt.setLayout(hbLayout);

    wgt.show();
    return app.exec();
}

this->layout()->addWidget(Table);

MdiChildJournal::MdiChildJournal(QWidget *parent):
    QMainWindow(parent)
{
    setAttribute(Qt::WA_DeleteOnClose);

    Table = new QTableWidget(this);
    Table->setColumnCount(4);
    Table->setRowCount(5);
   //qobject_cast<QMdiSubWindow*>(this)->widget; //НЕ ПРОКАТЫВАЕТ!!!
}

class MdiChildJournal: public QMdiSubWindow,QMainWindow
{

}