setTabOrder for button

[ecir.hana]

I try to jump with tab key between a QLineEdit and QPushButton but when I hit the key, the edit stays focused. This is the relevant code:

QWidget *widget = new QWidget(this);
    QVBoxLayout *vbox = new QVBoxLayout();
    widget->setLayout(vbox);
    QLineEdit *line = new QLineEdit();
    QPushButton *button = new QPushButton("click");
    vbox->addWidget(line);
    vbox->addWidget(button);
    setTabOrder(line, button);
    setTabOrder(button, line);
    setCentralWidget(widget);

QWidget *widget = new QWidget(this);
    QVBoxLayout *vbox = new QVBoxLayout();
    widget->setLayout(vbox);
    QLineEdit *line = new QLineEdit();
    QPushButton *button = new QPushButton("click");
    vbox->addWidget(line);
    vbox->addWidget(button);
    setTabOrder(line, button);
    setTabOrder(button, line);
    setCentralWidget(widget);

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Please, does anyone know what I'm doing wrong?