Using List Models as Data Sources in QML

Note: This is part of the Charts with QML Gallery example.

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

 ListModel {
     // Hard-coded test data
     ListElement { speedTrap:0; driver: "Fittipaldi"; speed:104.12 }
     ListElement { speedTrap:0; driver:"Stewart"; speed:106.12 }
     ListElement { speedTrap:0; driver:"Hunt"; speed:106.12 }
     ...
 // An example ListModel containing F1 legend drivers' speeds at speed traps
 SpeedsList {
     id: speedsList
     Component.onCompleted: {
         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: {
         root.currentIndex++;
         if (root.currentIndex < speedsList.count) {
             // Check if there is a series for the data already
             // (we are using driver name to identify series)
             var lineSeries = chartView.series(speedsList.get(root.currentIndex).driver);
             if (!lineSeries) {
                 lineSeries = chartView.createSeries(ChartView.SeriesTypeLine,
                                                     speedsList.get(root.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(speedsList.get(root.currentIndex).speedTrap,
                               speedsList.get(root.currentIndex).speed);

             if (speedsList.get(root.currentIndex).speedTrap > 3) {
                 chartView.axisX().max = Number(speedsList.get(root.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 = speedsList.get(root.currentIndex - 1).speedTrap;
         }
     }
 }