QScrollArea inside QGroupBox, scrollbars instead of resizing QGroupBox - c++

Question

I want to have a QScrollArea inside QGroupBox, so when I add new widgets to group box its size stays the same, but I have scroll bars instead of resizing group box itself.
Here's my code:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QtCore>
#include <QtGui>
#include <QLayout>
#include <QScrollArea>
#include <QGroupBox>
#include <QLabel>
#include <QLineEdit>
#include <QPushButton>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QGroupBox *box = new QGroupBox(QObject::tr("Example"));
QScrollArea *sa = new QScrollArea;
QGridLayout *gridLayout = new QGridLayout;
QPushButton *b1 = new QPushButton("A");
QPushButton *b2 = new QPushButton("B");
QPushButton *b3 = new QPushButton("C");
QPushButton *b4 = new QPushButton("D");
QPushButton *b5 = new QPushButton("E");
QPushButton *b6 = new QPushButton("F");
QPushButton *b7 = new QPushButton("F");
QPushButton *b8 = new QPushButton("F");
QPushButton *b9 = new QPushButton("F");
// addWidget(*Widget, row, column, rowspan, colspan)
// 0th row
gridLayout->addWidget(b1,0,0,1,1);
gridLayout->addWidget(b2,0,1,1,1);
gridLayout->addWidget(b3,0,2,1,1);
// 1st row
gridLayout->addWidget(b4,1,0,1,1);
// 2nd row with 2-column span
gridLayout->addWidget(b5,2,0,1,2);
// 3rd row with 3-column span
gridLayout->addWidget(b6,3,0,1,3);
gridLayout->addWidget(b7,4,0,1,3);
gridLayout->addWidget(b8,5,0,1,3);
gridLayout->addWidget(b9,6,0,1,3);
box->setLayout(gridLayout);
sa->setWidget(box);
setCentralWidget(sa);
}
MainWindow::~MainWindow()
{
delete ui;
}
What I have now is that every time I add a new QPushButton, QGroupBox resizes, no matther there is a QScrollArea. What should I change to have the behaviour I want? Is it possible?

Answer 1

That's because you are putting the groupbox inside the scroll area. Scroll area doesn't restrict its childrens size.
You should do the opposite, put scrollarea inside group box. Here is how;
QWidget* sw = new QWidget();
sw->setLayout(gridLayout);
sa->setWidget(cont);
QVBoxLayout* bl = new QVBoxLayout(box);
bl->addWidget(sa);
setCentralWidget(box);
Note that if you are using toggle buttons (such as radio button) they will not act as a group. Because technically they are not in the same QGroupBox any more - they are inside the scroll area. You can provide group behavior using a QButtonGroup instance.