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Qml F1 Legends

This application demonstrates how to use XmlListModel as a datasource for a Chart.

Running the Example

To run the example from Qt Creator, open the Welcome mode and select the example from Examples. For more information, visit Building and Running an Example.

Using List Models as Data Sources

Let's define an empty ChartView first:

ChartView {
    id: chartView
    title: "Driver Speeds, lap 1"
    anchors.fill: parent
    legend.alignment: Qt.AlignTop
    animationOptions: ChartView.SeriesAnimations
    antialiasing: true
}

Our XmlListModel uses hard-coded test data. In a real application the data source would be a timing system.

XmlListModel {
    // Hard-coded test data
    xml: "<results><row><speedTrap>0</speedTrap><driver>Fittipaldi</driver><speed>104.12</speed></row>"
        +"<row><speedTrap>0</speedTrap><driver>Stewart</driver><speed>106.12</speed></row>"
        +"<row><speedTrap>0</speedTrap><driver>Hunt</driver><speed>106.12</speed></row>"
    ...
    query: "/results/row"

    XmlRole { name: "speedTrap"; query: "speedTrap/string()" }
    XmlRole { name: "driver"; query: "driver/string()" }
    XmlRole { name: "speed"; query: "speed/string()" }
}
// An example XmlListModel containing F1 legend drivers' speeds at speed traps
SpeedsXml {
    id: speedsXml
    onStatusChanged: {
        if (status == XmlListModel.Ready) {
            timer.start();
        }
    }
}

The data is parsed with a timer. The line series representing each driver are created on the fly.

// A timer to mimic refreshing the data dynamically
Timer {
    id: timer
    interval: 700
    repeat: true
    triggeredOnStart: true
    running: false
    onTriggered: {
        currentIndex++;
        if (currentIndex < speedsXml.count) {
            // Check if there is a series for the data already
            // (we are using driver name to identify series)
            var lineSeries = chartView.series(speedsXml.get(currentIndex).driver);
            if (!lineSeries) {
                lineSeries = chartView.createSeries(ChartView.SeriesTypeLine,
                                                    speedsXml.get(currentIndex).driver);
                chartView.axisY().min = 0;
                chartView.axisY().max = 250;
                chartView.axisY().tickCount = 6;
                chartView.axisY().titleText = "speed (kph)";
                chartView.axisX().titleText = "speed trap";
                chartView.axisX().labelFormat = "%.0f";
            }
            lineSeries.append(speedsXml.get(currentIndex).speedTrap,
                              speedsXml.get(currentIndex).speed);

            if (speedsXml.get(currentIndex).speedTrap > 3) {
                chartView.axisX().max = Number(speedsXml.get(currentIndex).speedTrap) + 1;
                chartView.axisX().min = chartView.axisX().max - 5;
            } else {
                chartView.axisX().max = 5;
                chartView.axisX().min = 0;
            }
            chartView.axisX().tickCount = chartView.axisX().max - chartView.axisX().min + 1;
        } else {
            // No more data, change x-axis range to show all the data
            timer.stop();
            chartView.animationOptions = ChartView.AllAnimations;
            chartView.axisX().min = 0;
            chartView.axisX().max = speedsXml.get(currentIndex - 1).speedTrap;
        }
    }
}

Example project @ code.qt.io

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