Slider doesn't repaint on secondaryTrackValue update. #163971

import 'package:flutter/material.dart';

/// Flutter code sample for [Slider].

void main() => runApp(const SliderApp());

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

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

class SliderExample extends StatefulWidget {
  const SliderExample({super.key});

  @override
  State<SliderExample> createState() => _SliderExampleState();
}

class _SliderExampleState extends State<SliderExample> {
  double _currentSliderPrimaryValue = 0.0;
  double _currentSliderSecondaryValue = 0.0;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: const Text('Slider')),
      body: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          Slider(
            value: _currentSliderPrimaryValue,
            secondaryTrackValue: _currentSliderSecondaryValue,
            label: _currentSliderPrimaryValue.round().toString(),
            onChanged: (double value) {
              setState(() {
                _currentSliderPrimaryValue = value;
              });
            },
          ),
          ElevatedButton(
            onPressed: () {
              Future.delayed(const Duration(seconds: 1), () {
                setState(() => _currentSliderSecondaryValue = 0.2);
              });
            },
            child: Text('Update secondary value'),
          ),
        ],
      ),
    );
  }
}