- Qt 6.8
- Qt Charts
- Using List Models as Data Sources in QML
- Qt Charts | Commercial or GPLv3

# 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;
             }
         }
     }