iOS and Android: context menu does not show (Qt::ActionsContextMenu)

#include <QApplication>
#include <QLabel>
#include <QMenu>
#include <QAction>

class Label : public QLabel
{
    Q_OBJECT
public:
    Label(QWidget *parent = 0)
        : QLabel(parent)
    {
        setText("init");
        setAlignment(Qt::AlignCenter);
        QStringList cities;
        cities << "Oslo";
        cities << "Berlin";
        cities << "Moscow";
        cities << "Helsinki";
        cities << "Santa Clara";
        for (int i = 0; i < cities.count(); ++i) {
            QAction *action = new QAction(cities[i], this);
            connect(action, SIGNAL(triggered()), SLOT(chooseCity()));
            addAction(action);
        }
        setContextMenuPolicy(Qt::ActionsContextMenu);
    }

protected slots:
    void chooseCity() {
        QAction *action = qobject_cast<QAction*>(sender());
        if (action)
            setText(action->text());
    }
};

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Label w;
    w.resize(200, 200);
    w.show();
    return a.exec();
}

#include "main.moc"