How to implement API data in a line chart

I just post the code example in here. If you have any question, you can ask me and I will try to answer the question I can because this code is like almost 2 or 3 years old now and I did not work on this project anymore. Hope the code below helps you!

import 'package:charts_flutter/flutter.dart';
import 'package:flutter/material.dart';
import 'package:provider/provider.dart';
import 'package:charts_flutter/flutter.dart' as charts;
import 'package:intl/intl.dart';

import 'custom_symbol_renderer.dart';
import 'package:orbital_app/Model/tank_ping.dart';
import 'package:orbital_app/Provider/api_provider.dart';

class TankChart extends StatefulWidget {
  //This is my API class object to extract the data
  TankChart({Key key}) : super(key: key);
  @override
  _TankChartState createState() => _TankChartState();
}

class _TankChartState extends State<TankChart> {
  var ping;
  var tankInfo;
 
  // Since I am using a Provider in this code, I call the API here
  getPingProvider(){
    setState((){
      ping = Provider.of<TankPingProvider>(context, listen: false);
      ping.getTankPing(context);
    });
  }

  getInfoProvider(){
    setState((){
      tankInfo = Provider.of<TankInfoProvider>(context, listen: false);
      tankInfo.getTankInfo(context);
    });
  }

  @override
  initState() {
    super.initState();
    getPingProvider();
    getInfoProvider();
  } 

  @override
  Widget build(BuildContext context) {
    
    // Here I format the time to normal human time
    final numericFormatter = charts.BasicNumericTickFormatterSpec.fromNumberFormat(
      NumberFormat.compact()
    );
    final ping = Provider.of<TankPingProvider>(context);
    return  ListView.builder(
      padding: EdgeInsets.zero,

      // Here I want everything to be shrink and expand when the user needs it
      shrinkWrap: true,

      // Here is where I set whether the graph can be expand by user vertical 
      // scroll
      physics: NeverScrollableScrollPhysics(),

      //The data from the API is here
      itemCount: ping.tankPing.length,
      itemBuilder: (context, index){
        if(ping.tankPing.length == null){
          return CircularProgressIndicator();
        } else if(ping.tankPing == null){
          return  CircularProgressIndicator();
        } else{
          int no = index + 1;
          final size = MediaQuery.of(context).size;
          
          // Here is the API dot or data dot on the graph
          List<charts.Series<TankPing, DateTime>> series = [
              charts.Series(
                id: '${tankInfo.tankInfos.data[index].name}',
                data: ping.tankPing[no.toString()],
                colorFn: (_, __) => MaterialPalette.blue.shadeDefault,
                domainFn: (TankPing ping, _) => ping.trackedAt,
                measureFn: (TankPing ping, _) => ping.volume
              ),
            ];

            return Container(
              height: 250,
              child: Card(
                child: Column(
                  children: [
                    Expanded(
                      child: Padding(
                        padding: const EdgeInsets.only(
                          left: 5
                        ),
                        child: charts.TimeSeriesChart(
                          series,
                          animate: false,
                          domainAxis: charts.DateTimeAxisSpec(
                            tickFormatterSpec: charts.AutoDateTimeTickFormatterSpec(
                              day: charts.TimeFormatterSpec(
                                format: 'dd',
                                transitionFormat: 'dd MMM',
                              ),
                            ),
                          ),
                          primaryMeasureAxis: charts.NumericAxisSpec(
                            tickFormatterSpec: numericFormatter,
                            renderSpec: charts.GridlineRendererSpec(
                              // Tick and Label styling here.
                              labelStyle: charts.TextStyleSpec(
                                fontSize: 10, // size in Pts.
                                color: charts.MaterialPalette.black
                              ),
                            )
                          ),
                          defaultRenderer: charts.LineRendererConfig(
                            includeArea: true,
                            includeLine: true,
                            includePoints: true,
                            strokeWidthPx: 0.5,
                            radiusPx: 1.5
                          ),
                          dateTimeFactory: const charts.LocalDateTimeFactory(),
                          behaviors: [
                            charts.SlidingViewport(),
                            charts.PanAndZoomBehavior(),
                            charts.SeriesLegend(
                              position: charts.BehaviorPosition.top,
                              horizontalFirst: false,
                              cellPadding: EdgeInsets.only(
                                left: MediaQuery.of(context).size.width * 0.27, 
                                top: 15
                              ),
                            ),
                            charts.SelectNearest(
                              eventTrigger: charts.SelectionTrigger.tap
                            ),
                            charts.LinePointHighlighter(
                              symbolRenderer: CustomCircleSymbolRenderer(size: size),
                            ),
                          ],
                          selectionModels: [
                            charts.SelectionModelConfig(
                            type: charts.SelectionModelType.info,
                            changedListener: (charts.SelectionModel model) {
                              if(model.hasDatumSelection) {
                                final tankVolumeValue = model.selectedSeries[0].measureFn(model.selectedDatum[0].index).round();
                                final dateValue = model.selectedSeries[0].domainFn(model.selectedDatum[0].index);
                                CustomCircleSymbolRenderer.value = '$dateValue \n $tankVolumeValue L';
                              }
                            })
                          ]),
                      ),
                      ),
                    ],
                  ),
              ),
            );
          }
        });
  }
}

The answer is use the min and max value to determine how long the data will be. And then just use the flSpot to enter your data.