qt拖动窗口

void a::mousePressEvent(QMouseEvent *event)
{

    if(event->button()==Qt::LeftButton && event->pos().y()<(this->height()-mainWidget->height()))
    {

        m_dragging=true;
        m_dragStarPos=event->pos();
    }
}
void a::mouseMoveEvent(QMouseEvent *event)
{
    if(m_dragging==true)
    {
        this->move(event->globalPos()-m_dragStarPos);
    }
}
void a::mouseReleaseEvent(QMouseEvent *event)
{
    if(event->button()==Qt::LeftButton)
    {
        m_dragging=false;
    }
}

头文件

private:
    bool m_dragging=false;
    QPoint m_dragStarPos;


protected:
    void mousePressEvent(QMouseEvent *event);
    void mouseMoveEvent(QMouseEvent *event);
    void mouseReleaseEvent(QMouseEvent *event);