QLPreviewView cannot display after insert to QStackedWidget

[iwant]

I'm trying to use QLPreviewView to preview keynote/PDF file on mac.
I found it's work fine to insert a QLPreviewView into a QWidget , code like:

QWidget* widget = new QWidget();
widget->setGeometry(0, 0, 500, 500);
NSView* nativeView = reinterpret_cast<NSView*>(widget->winId());
[nativeView addSubView: myQLPreviewView];
widget->show();

But when I tryed to insert the widget into a QStackedWidget, I found that nothing displayed at last:

QStackedWidget* sw= new QStackedWidget();
sw->setGeometry(0, 0, 500, 500);
sw->insertWidget(0, widget)
sw->setCurrentIndex(0);
sw->show();

Here is the different from Debug View Hierarchy:
Insert to qwidget:

After insert widget(with QLPreviewView) to QStackedWidget:

[SGaist]

Hi and welcome to devnet,

What is QLPreviewView ?

[ChrisW67]

Seems to be an Apple OS widget: QL = Quick Look