void Qmy_Widget::mouseMoveEvent(QMouseEvent *event){
    if(event->buttons()&&Qt::LeftButton){
        int x,y;
        x=event->pos().x()-mpos.x()+this->parentWidget()->geometry().left()-this->geometry().left();
        y=event->pos().y()-mpos.y()+this->parentWidget()->geometry().top()-this->geometry().top();

        this->parentWidget()->move(x,y);
    }

}

void Qmy_Widget::mousePressEvent(QMouseEvent *event){
    mpos = event->pos();
}

class Qmy_Widget:public QWidget{
//    Q_OBJECT
protected:
    void mousePressEvent(QMouseEvent *event);
    void mouseMoveEvent(QMouseEvent *event);
public:
    QPoint mpos;
};