Qt自定义Widget中设置滚动条

用代码自定义一个独立显示的Widget，要在里面画图，同时加上滚动条，

滚动条：

　　 printerYuLanPainter  = new QPainter();
    test = new QScrollArea();
    printerYuLanWidget = new QWidget(test);
    printerYuLanWidget->setMaximumSize(720,1000);
    printerYuLanWidget->setMinimumSize(720,1000);

    printerYuLanWidget->close();
    test->setWidget(printerYuLanWidget);

画图：

this->printerYuLanWidget->installEventFilter(this);//注册触发机制

//重写eventFilter
bool MainWindow::eventFilter(QObject *watched, QEvent *e)
{
    
    if(watched == this->printerYuLanWidget)
    {
        if(e->type() == QEvent::Paint)
        {
            qDebug()<<"this->printerYuLanWidget" << this->printerYuLanWidget->width()<< "    "<<this->printerYuLanWidget->height();

            printTest(this->printerYuLanPainter,this->printerYuLanWidget);
            return true;
        }
    }

    return QWidget::eventFilter(watched, e);
}

printTest函数为绘图函数。