Qt 5.13 | Qt Charts | Qml F1 Legends

Qt Charts | Commercial or GPLv3

# 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