Dynamically update Flutter animations by changing Tween begin and end value.

main.dart

import 'package:flutter/material.dart';

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

class MyApp extends StatefulWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      debugShowCheckedModeBanner: false,
      home: Scaffold(
        backgroundColor: Color(0xFFDCE2E1),
        body: Center(child: SomeAnimation()),
      ),
    );
  }
}

class SomeAnimation extends StatefulWidget {
  const SomeAnimation({Key? key}) : super(key: key);

  @override
  State<SomeAnimation> createState() => _SomeAnimationState();
}

class _SomeAnimationState extends State<SomeAnimation>
    with SingleTickerProviderStateMixin {
  late final controlller = AnimationController(
    vsync: this,
    duration: const Duration(seconds: 1),
  );

  late final Tween<double> someTween = Tween(begin: 0.0, end: 1.0);
  late final animation = controlller.drive(someTween);

  @override
  void initState() {
    super.initState();
    controlller.repeat(reverse: true);
  }

  @override
  void dispose() {
    controlller.dispose();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.all(64.0),
      child: Column(
        children: [
          Expanded(
            child: Center(
              child: ScaleTransition(
                scale: animation,
                child: const Text(
                      'Tween',
                      style: TextStyle(),
                    ),
              ),
            ),
          ),
          Row(
            children: [
              const SizedBox(
                width: 100,
                child: Text(
                  'begin',
                  style: TextStyle(fontSize: 32, ),
                ),
              ),
              Expanded(
                child: SomeSlider(
                  onChange: (value) {
                    someTween.begin = value;
                  },
                ),
              ),
            ],
          ),
          Row(
            children: [
              const SizedBox(
                width: 100,
                child: Text(
                  'end',
                  style: TextStyle(fontSize: 32,),
                ),
              ),
              Expanded(
                child: SomeSlider(
                  onChange: (value) {
                    someTween.end = value;
                  },
                ),
              ),
            ],
          ),
        ],
      ),
    );
  }
}

typedef DoubleCallback = void Function(double value);

class SomeSlider extends StatefulWidget {
  const SomeSlider({
    Key? key,
    required this.onChange,
  }) : super(key: key);

  final DoubleCallback onChange;

  @override
  State<SomeSlider> createState() => _SomeSliderState();
}

class _SomeSliderState extends State<SomeSlider> {
  double value = 1;

  void onChange(double value) {
    setState(() {});
    this.value = value;
    widget.onChange(value);
  }

  @override
  Widget build(BuildContext context) {
    return Slider(
      min: 0,
      max: 30,
      value: value,
      onChanged: onChange,
    );
  }
}