问Qt -无法获得父部件

EN

gui.h

class ClickableLabel : public QLabel
{
    Q_OBJECT
public:
    explicit ClickableLabel(Card card,const QString& text="", QWidget* parent=0);
    ~ClickableLabel();
signals:
    void clicked(const QString &text);

protected:

private:
    QSignalMapper *signalMapper;
};

ClickableLabel::ClickableLabel(Card card,const QString& text,QWidget* parent) : QLabel(parent)
{
    QWidget *w = this->parentWidget();
    Q_ASSERT(w);
}

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    gui w;

    QList<QVBoxLayout*> layouts = w.findChildren<QVBoxLayout*>();
    layouts[0]->addWidget(new ClickableLabel("myLabel"));

    w.show();
    return a.exec();
}