main.dart

import 'package:flutter/material.dart';
import 'package:fl_chart/fl_chart.dart';

void main() {
  runApp(MyApp());
}

class YourData {
  final double date;
  final double value;

  YourData(this.date, this.value);
}

class MyApp extends StatelessWidget {

  final List<YourData> myDataList = [
    YourData(202012.0, 8465.696263643998),
    YourData(202101.0, 7771.7867338371125),
    YourData(202102.0, 8789.520710887211),
  ];

  List<FlSpot> mapMyDataToFlSpots(List<YourData> data) {
    return data.asMap().entries.map((entry) {
      final index = entry.key;
      final myData = entry.value;
      return FlSpot(index.toDouble(), myData.value);   
    }).toList();
  }
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        body: Center(
          child: Padding(
            padding: EdgeInsets.only(right: 60, left: 22),
            child: AspectRatio(
              aspectRatio: 1,
              child: LineChart(
                LineChartData(
                  lineBarsData: [
                    LineChartBarData(
                      spots: mapMyDataToFlSpots(myDataList)
                    )
                  ],
                  titlesData: FlTitlesData(
                    show: true,
                    bottomTitles: SideTitles(
                      showTitles: true,
                      getTitles: (x) {
                        final myDataAtThisX = myDataList[x.toInt()];
                        return myDataAtThisX.date.toString();
                      }
                    )
                  )
                )
              ),
            ),
          ),
        ),
      ),
    );
  }
}