I assume it does print the qDebug() << "hello1"; and hello2 ?

Is there anything special with item2Configuration and item3Configuration.

I mean like doing something in their constructor?

By commenting/compiling I have managed to understand who is causing the problem.
This is what the SLOT function looks like now:

void ConfigurationDialog::onListItemClicked(QListWidgetItem* item)
{
ui.stackedWidget->setCurrentIndex(ui.listWidget->currentRow());

if (ui.stackedWidget->currentIndex() == 0)
{
	item1Configuration* item1Widget = new item1Configuration;
	ui.stackedWidget->addWidget(item1Widget);
	ui.stackedWidget->setCurrentWidget(item1Widget);
}
else if (ui.stackedWidget->currentIndex() == 1)
{
	/*item2Configuration* item2Widget = new item2Configuration;
	ui.stackedWidget->addWidget(item2Widget);
	ui.stackedWidget->setCurrentWidget(item2Widget);*/
	qDebug() << "hello1";
}
else if (ui.stackedWidget->currentIndex() == 2)
{
	/*item3Configuration* item3Widget = new item3Configuration;
	ui.stackedWidget->addWidget(item3Widget);
	ui.stackedWidget->setCurrentWidget(item3Widget);*/
	qDebug() << "hello2";
}
else if (ui.stackedWidget->currentIndex() == 3)
{
	item4Configuration* item4Widget = new item4Configuration;
	ui.stackedWidget->addWidget(item4Widget);
	ui.stackedWidget->setCurrentWidget(item4Widget);
}
else if (ui.stackedWidget->currentIndex() == 4)
{
	item5Configuration* item5Widget = new item5Configuration;
	ui.stackedWidget->addWidget(item5Widget);
	ui.stackedWidget->setCurrentWidget(item5Widget);
}

}

This works well: the correct widget is shown when the corresponding item is selected in the qListWidget. The problem comes from Item2 and Item3 for some reason (that's why I commented them out). I do not understand what the problem could be. They are both QWidget classes created just like items 1,4,5. If included in the code they make the application freeze and then crash. Any thoughts?

try use the debugger to see where it crashes.

Do you make a ConfigurationDialog in main.cpp and use instead of a MainWindow ?

Did you change anything else as I dont see the code you shown should crash even before you click on stuff.

ConfigurationDialog::ConfigurationDialog(QWidget* parent)
: QDialog(parent)
{
ui.setupUi(this);
setWindowFlags(Qt::WindowStaysOnTopHint);

ui.listWidget->addItem("Text1");
ui.listWidget->addItem("Text2");
ui.listWidget->addItem("Text3");
ui.listWidget->addItem("Text4");
ui.listWidget->addItem("Text5");

item1Configuration* item1 = new item1Configuration;
item2Configuration* item2 = new item2Configuration;
item3Configuration* item3 = new item3Configuration;
item4Configuration* item4 = new item4Configuration;
item5Configuration* item5 = new item5Configuration;

ui.stackedWidget->addWidget(item1);
ui.stackedWidget->addWidget(item2);
ui.stackedWidget->addWidget(item3);
ui.stackedWidget->addWidget(item4);
ui.stackedWidget->addWidget(item5);


connect(ui.listWidget, SIGNAL(itemClicked(QListWidgetItem*)),
	this, SLOT(onListItemClicked(QListWidgetItem*)));

}

ConfigurationDialog::~ConfigurationDialog()
{
}

void ConfigurationDialog::onListItemClicked(QListWidgetItem* item)
{
ui.stackedWidget->setCurrentIndex(ui.listWidget->currentRow());
}

Now I think the logic is correct (I have also implemented the SIGNAL/CONTROL as you suggested). The problem is that the application does not open anymore when I compile. Instead after a little bit of waiting a window opens up with the following error:

Unhandled exception at 0x00007FFD5793B866 (ntdll.dll) in Application.exe: 0xC00000FD: Stack overflow (parameters: 0x0000000000000001, 0x000000190E003FF8).

As @Pl45m4 suggests, you will have to write some code yourself. Designer does not generate anything code wise with regard to interaction.

You can click all you want on the items of your QListWidget, it will have no effect on the QStackedWidget.

You have to implement a slot that will switch the QStackedWidget current widget based on the item you clicked.

You haven't read the signal & slot doc?! It probably helps you to understand the mechanism better.

A slot is pretty much a function that is called every time you "fire" (emit) the signal.
So you could make a connection to show the correct page of your stackedWidget depending on which item or button you click.

arincWidget->show();

Showing the arincWidget does not help in your case. You want to show the stackedWidget page with the widget, not the widget itself right?

Now I need to understand how to have it only show up when the first item is selected inside the dialog's list.

You can flip the pages according to your clicked items using signals & slots.

• https://doc.qt.io/qt-5/signalsandslots.html

Edit:

Do you have any layout in your UI?

Arinc424Configuration* arincWidget = new Arinc424Configuration();
ui.stackedWidget->addWidget(arincWidget);
arincWidget->show();

In the dialog.cpp file. Now I need to understand how to have it only show up when the first item is selected inside the dialog's list.

My Item1 is a Qwidget Class.

How does your (G)UI for your dialog look like? What type of class is Item1?