Qt实践之用鼠标事件使QChart图表前移后移、时间坐标轴放大缩小

头文件声明

protected:
    void wheelEvent(QWheelEvent *event) override;
private slots:
    void onTimeout();
private:
    void dragPressureChart(int delta);
    void zoomPressureChart(QWheelEvent *wheelEvent);
    void showStreamStatusChart();
    
	int m_totalDelta;  		//记录前移或后移的时间刻度
	QTimer *m_timer;

成员变量初始化

 m_totalDelta = 0;
 m_timer = new QTimer();
 QObject::connect(m_timer, &QTimer::timeout, this, &StatusPanel::onTimeout);
 m_timer->start(1000);

实现滚轮事件

void StatusPanel::wheelEvent(QWheelEvent *event)
{
    if (m_statusChartView->geometry().contains(m_statusChartView->mapFrom(this, event->position().toPoint())))
    {
        if (event->modifiers() & Qt::ControlModifier)
        {
            zoomPressureChart(event);	// CTRL加滚动，放大或缩小坐标轴的范围
        }
        else
        {
            dragPressureChart(event->angleDelta().y());		// 单独滚动，前移或后移图表曲线，当滚轮上滚时参数为120，反之为-120
        }
    }
    event->accept();	//来接受事件，表示事件已经被处理。如果不调用该函数，事件会继续传递给其他可能处理该事件的控件
}

实现前移后移图表曲线

void StatusPanel::dragPressureChart(int delta)
{
    if (delta > 0 && m_totalDelta < 1800) // 30 minutes, scroll up		// 允许前移或后移的范围为30分钟
    {
        m_axisX->setMin(m_axisX->min().addSecs(-60));
        m_axisX->setMax(m_axisX->max().addSecs(-60));
        m_totalDelta += 60;
    }
    else if (delta < 0 && m_totalDelta > -1800) // scroll down
    {
        m_axisX->setMin(m_axisX->min().addSecs(60));
        m_axisX->setMax(m_axisX->max().addSecs(60));
        m_totalDelta -= 60;
    }
}

实现放大缩小时间坐标轴

void StatusPanel::zoomPressureChart(QWheelEvent *wheelEvent)
{
    static int axisRange[3] = {3, 5, 10};		// 时间轴改变的幅度共三档，3*2， 5*2， 10*2
    static int wheelCount = 0;		// 记录滚轮有效滚动次数
    static int callCount = 0;		//记录函数调用次数，每调用三次，有效滚动次数加一，坐标轴改变一次

    callCount++;
    if (callCount >= 3)
    {
        wheelCount++;
        Count = 0;
        if (wheelCount < 0)
        {
            wheelCount = -wheelCount;
        }
        if (wheelCount > 2)
        {
            wheelCount = 0;
        }
        QDateTime min = QDateTime::currentDateTime().addSecs(-60 * axisRange[wheelCount]);
        QDateTime max = QDateTime::currentDateTime().addSecs(60 * axisRange[wheelCount]);
        m_axisX->setRange(min, max);
        m_totalDelta = 0;		// 清零，表示当前无前移或后移曲线
    }
}

实现定时器事件，实时更新以时间为坐标轴表示的图表

void MyClass::onTimeout()
{
	showStreamStatusChart();
}

定时器事件实际要做的是从界面获取数据源，并根据数据源实时更新图表曲线，每次使曲线前进一分钟

void MyClass::showStreamStatusChart()
{
	QLineSeries *dataSeries = dynamic_cast<QLineSeries *>(m_statusChart->series().at(streamIndex));
    m_axisX = qobject_cast<QDateTimeAxis *>(m_statusChart->axisX(dataSeries));
    QDateTime currentTimePoint = QDateTime::currentDateTime();

    if (currentTimePoint.secsTo(m_axisX->min()) < -3 * 60)
    {
        if (currentTimePoint.operator>=(m_axisX->min()) && currentTimePoint.operator<=(m_axisX->max()))
        {
            QDateTime newMax = m_axisX->max().addSecs(60);
            if (newMax <= currentTimePoint.addSecs(90))
            {
                m_axisX->setMin(m_axisX->min().addSecs(60));
                m_axisX->setMax(newMax);
            }
        }
        else if (currentTimePoint.secsTo(m_axisX->min()) < -31 * 60)		//	使图表只保留前后30分钟的数据
        {
            m_axisX->setMin(m_axisX->min().addSecs(60));
            m_axisX->setMax(m_axisX->max().addSecs(60));
        }
    }
        double currentPressure =  m_ui->labelPump1Pressure->text().toDouble(); 		// 从界面获取图表曲线的数据源
        dataSeries->append(QDateTime::currentMSecsSinceEpoch(), currentPressure);
    	dataSeries->show();
}