Showcase some points and enable default interactions after the first user interaction, #1873

gistfile1.txt

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

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  const HomePage({
    super.key,
    this.defaultShowingPointIndex = 7,
    this.data = const [1, 2, 2, 4, 3, 6, 5, 8, 5, 6, 4],
  });

  final int defaultShowingPointIndex;
  final List<double> data;

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  bool firstInteractionHappened = false;

  @override
  Widget build(BuildContext context) {
    final mainLineBar = LineChartBarData(
      spots: widget.data.asMap().entries.map((entry) {
        final index = entry.key;
        final value = entry.value;
        return FlSpot(index.toDouble(), value);
      }).toList(),
      showingIndicators: firstInteractionHappened
          ? []
          : [
              widget.defaultShowingPointIndex,
            ],
    );
    return Scaffold(
      body: Center(
        child: AspectRatio(
          aspectRatio: 2.0,
          child: LineChart(
            LineChartData(
              minX: 0,
              maxX: 10,
              minY: 0,
              maxY: 10,
              lineBarsData: [mainLineBar],
              lineTouchData: LineTouchData(
                handleBuiltInTouches: firstInteractionHappened,
                touchCallback: firstInteractionHappened
                    ? null
                    : (
                        FlTouchEvent event,
                        LineTouchResponse? touchResponse,
                      ) {
                        if (event is FlTapUpEvent) {
                          setState(() {
                            firstInteractionHappened = true;
                          });
                        }
                      },
              ),
              showingTooltipIndicators: firstInteractionHappened
                  ? []
                  : [
                      ShowingTooltipIndicators([
                        LineBarSpot(
                          mainLineBar,
                          0,
                          mainLineBar.spots[widget.defaultShowingPointIndex],
                        ),
                      ]),
                    ],
            ),
          ),
        ),
      ),
    );
  }
}

Answered to #1873

CleanShot.2025-04-13.at.23.24.26.mp4