How to disable trackball tooltip for particular series in Flutter Cartesian charts ?

In this article, we describe how to disable the trackball tooltip for a particular series in the Cartesian charts.

Flutter Cartesian chart widget provides support for customizing the trackball in the chart using callback events on rendering. Callback events are functions or methods that you pass as arguments into another function or method and can perform an action when required. Similarly, you can customize the trackball tooltip to render only for particular series of your choice in the chart using the onTrackballPositionChanging callback event.

For example, consider a chart with two Cartesian series - line and area series. If you need to show data point values only for the area series using the trackball tooltip, you can use the onTrackballPositionChanging event to modify the arguments accordingly.

Refer the following instructions to customize the trackballs tooltip to render for particular series in the chart using their callback event.

Customization of trackballs tooltip to render for a particular series

Step 1: Initialize the SfCartesianChart with TrackballBehavior enabled as true and with two series types (say line and area series). For customizing the trackballs tooltip to render only for the area series.

late TrackballBehavior _trackballBehavior;
 
@override
void initState(){
  _trackballBehavior = TrackballBehavior(enable: true);
  super.initState();
}
 
@override
 Widget build(BuildContext context) {
  return SfCartesianChart(
            primaryXAxis: CategoryAxis(),
            trackballBehavior: _trackballBehavior,
            series: <LineSeries<ChartData, String>>[
              LineSeries<ChartData, String>(
                  dataSource: chartData1,
                  name: 'Line',
                  xValueMapper: (ChartData data, _) => data.x,
                  yValueMapper: (ChartData data, _) => data.y
              ),
              AreaSeries(
                dataSource: ChartData2,
                name: 'Area', 
                xValueMapper: (ChartData data, _) => data.x, 
                yValueMapper: (ChartData data, _) => data.y
             )
            ]
)

Step 2: Define the onTrackballPositionChanging event in the SfCartesianChart and using the chartPointInfo argument, get the series argument (for accessing all the elements of the series in the chart) and store in a variable of type ChartSeries<dynamic, dynamic>. After that, check if the series name is equal to the name of the line series or not for setting the header and label values of the chartPointInfo argument as null or empty string.

By setting empty string or null values to the header and label when the series name equals the line series name, the trackball tooltip will only render for the area series and not for the line series.

Screenshots

Trackballs tooltip rendered only for Area series

For more information on tooltip public method, please refer to our user guide.