QT 标題欄隐藏可拖拽

void mousePressEvent(QMouseEvent *e);
    void mouseMoveEvent(QMouseEvent *e);
    void mouseReleaseEvent(QMouseEvent *e);
    QPoint last;      

void AddDialog::mousePressEvent(QMouseEvent *e)
{
    last = e->globalPos();
}
void AddDialog::mouseMoveEvent(QMouseEvent *e)
{
    int dx = e->globalX()-last.x();
    int dy = e->globalY()-last.y();
 
    last = e->globalPos();
    move(x()+dx,y()+dy);
}
void AddDialog::mouseReleaseEvent(QMouseEvent *e)
{
    int dx = e->globalX()-last.x();
    int dy = e->globalY()-last.y();
 
    last = e->globalPos();
    move(x()+dx,y()+dy);
}