QScrollArea derivative is empty if it's created from an .ui file

Question

Consider following simple example:

Area.hh

#pragma once

class Area;

#include <QScrollArea>

class Area : public QScrollArea {

    Q_OBJECT

public:

    Area (QWidget *_parent = 0);
};

Area.cc

#include "main.hh"
#include "Area.hh"

#include <QLabel>

Area::Area (QWidget *_parent) :
    QScrollArea (_parent)
{
    QLabel *label = new QLabel ("Show me please");
    setWidget (label);
}

This scroll area should show a label inside it. And it does so well if you just create an Area object and show it like this:

Area *area = new Area();
area->show();

However, if you add a QScrollArea with Qt Creator and promote it to Area class, then it shows nothing inside and there are no scrollbars. What can I do to show it properly?

Answer 1

Qt Designer adds an empty widget inside the QScrollArea, overwriting yours.

To prevent that, use a base QWidget instead of a QScrollArea, and promote that widget to an Area class. Qt's Ui compiler won't considered it to be a QScrollArea, so it won't generate a call to setWidget anymore.