Get a notification/event/signal when a Qt widget gets focus

Qt widget gets focus  on  event filter.

The  application written with the  QtCreator  and form the  QComboBox named combobox.

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    ui->comboBox->installEventFilter(this);
    .
    .
    .
}
bool MainWindow::eventFilter(QObject *object, QEvent *event)
{
    if (event->type() == QEvent::FocusOut)
    {
        if (object == ui->comboBox)
        {
            qWarning(object->objectName().toLatin1().data());
        }
    }
    return false;
}

The level of WYSIWYG programe is:

In C++,

class LineEdit : public QLineEdit
{
    virtual void focusInEvent( QFocusEvent* )
    {}
};

The alternative answer is:

   By  focusChangedsignal  through sending by the focus changes  and  has two arguments  one is widget losing focus and the one is gaining focus.

void QApplication::focusChanged(QWidget * old, QWidget * now)