QML F1 图例

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

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使用列表模型作为数据源

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;
        }
    }
}
					

范例工程 @ code.qt.io

内容

• 运行范例

• 使用列表模型作为数据源