一、概述

Qt继承 QChartView 重写 paintEvent 函数后，容易出现两个问题：

a、Painter not active问题；

b 、QChartView原有的图形不显示了。

继承 QChartView 重写 paintEvent 函数时出现以下错误信息。

QWidget::paintEngine: Should no longer be called
QPainter::begin: Paint device returned engine == 0, type: 1
QPainter::setRenderHint: Painter must be active to set rendering hints
QPainter::translate: Painter not active
QPainter::setPen: Painter not active
QPainter::drawPath: Painter not active

 paintEvent 函数

void ChartView::paintEvent(QPaintEvent *event)
{
    if(m_press)
    {
        QPainter painter(this);
        painter.setRenderHint(QPainter::Antialiasing);

        QPen pen;
        pen.setWidth(2);
        pen.setColor(QColor(255,255,255));
        pen.setStyle(Qt::DashDotLine);
        painter.setPen(pen);
        QRect tempRt(m_startPT, m_endPT);
        painter.drawRect(tempRt);
    }
}

 解决办法：

问题a 解决方法：
        将QPainter painter(this);改为 QPainter painter(viewport());即可。

问题b 解决方法：

        在需要添加    QChartView::paintEvent(event);

更改后

void ChartView::paintEvent(QPaintEvent *event)
{
    QChartView::paintEvent(event);
    if(m_press)
    {
        QPainter painter(viewport());
        painter.setRenderHint(QPainter::Antialiasing);
        QPen pen;
        pen.setWidth(2);
        pen.setColor(QColor(255,255,255));
        pen.setStyle(Qt::DashDotLine);
        painter.setPen(pen);

        QRect tempRt(m_startPT, m_endPT);
        painter.drawRect(tempRt);
    }
}