QDateTimeAxis starts in default date time (01-01-1970 01:00)

diego-qt

Hello, I'm trying to plot a QChart with date-time horizontal axis and value vertical axis. I'm having trouble with the horizontal axis as I can't make it start with the current time. Here is my code:

Chart::Chart(): QWidget(), axisX(new QDateTimeAxis), axisY(new QValueAxis),
chart(new QChart), chartView(new QChartView)
{
    chart->addSeries(lineSeries);
    chart->legend()->hide();

    //format the time axis
    axisX->setFormat("dd.MM.yyyy HH:mm");
    axisX->setTitleText("Time");
    axisX->setLabelsAngle(-90);
    QDateTime timeValue(QDate::currentDate(), QTime::currentTime());
    axisX->setRange(timeValue, timeValue);
    chart->addAxis(axisX, Qt::AlignBottom);
    lineSeries->attachAxis(axisX);
    qDebug() << timeValue;

    //format the temperature axis
    axisY->setLabelFormat("%i");
    axisY->setTitleText("Temperature (°C)");
    axisY->setTickInterval(5);
    axisY->setRange(0, 40);
    chart->addAxis(axisY, Qt::AlignLeft);
    lineSeries->attachAxis(axisY);

    //place the chart in the window
    QVBoxLayout *layout = new QVBoxLayout(this);
    layout->addWidget(chartView, 0);
    resize(500, 500);
}

This shows a chart where the range is the default date time 01-01-1970 01:00, even thought qDebug() tells me that timeValue is set to the current time. How can I solve this?

One possible solution is in the function that adds a real value to the series (with lineSeries.append(...)) and updates the max value of the horizontal axis.

void Chart::addValueToChart(qreal newTempValue)
{
    QDateTime current(QDate::currentDate(), QTime::currentTime());
    lineSeries->append(current.toMSecsSinceEpoch(), newTempValue);
    axisX->setMax(current);
}

I could be able to update the min value of this axis in this function too, but I think that updating it every single time would be a waste of time. The ideal would be to set the min date-time value one time. Would that be possible?

SGaist

Hi,

Just to check, what happens if you configure your axis after you set it on the chart ?