How to display Widgets in the midle of a Window

[revellix]

Following problem:

I want to display a widget in the middle of a QMdiSubWindow. I also want to use Tabs later. Therefore I add a QStackWidget to a QMdiSubWindow. The first QStackWidget is a Widget I constructed called inAOrifice. Now in the Fullscreenmode the inAOrifice Widget isnt that big and I want to display it in the middle of the QMdiSubWindow, in the QStackWidget respectively. It always appears in the left upper corner. Any suggestions? I have tried a lot already. Cant see my mistake...

Most common code yet ...

@MainChild::MainChild(QWidget *parent) : QMdiSubWindow(parent)
{
this->setAttribute(Qt::WA_DeleteOnClose);

inAOrifice = new inputAOrifice(this);
stackLayout = new QVBoxLayout(this);
stackWidget = new QStackedWidget;

stackWidget->addWidget(inAOrifice);
stackLayout->setAlignment(stackWidget,Qt::AlignCenter);
this->setWidget(stackWidget);

}@

EDIT:

isnt it used when I call with parent widget...

stackLayout = new QVBoxLayout(this);

I already tried to set the Layout with

this->setLayout.... no effect. the widget doesnt appear.

[Eddy]

You didn't use stackLayout.