Can't pass the flutter slider value to int-CodePudding

inital value of _value is 200, but when i change the value with the slider, it does not pass it to the controller (i mean because of init it takes as default 200 and never changes)

  int _value = 200;

  @override
  void initState() {
    super.initState();
    _yellowController = AnimationController(
        duration: Duration(milliseconds: _value), vsync: this)
      ..addListener(() {
        setState(() {});
      });
  }

Slider(
                min: 200,
                max: 2000,
                activeColor: Colors.black54,
                inactiveColor: Colors.black12,
                thumbColor: Colors.black,
                value: _value.toDouble(),
                onChanged: (value) {
                  _value = value.round();
                  setState(() {});
                },
              ),

CodePudding user response：

You need to delete setState(() {}); into addListener code. Because it's doing automatically. If you do setState in addListener code it's rebuild again and returns to starting position

CodePudding user response：

You can see this StackOverflow answer that you can just change the _yellowController.duration and animate foward/reverse/repeat again. Try this code on https://dartpad.dev/ :

import 'package:flutter/material.dart';

const Color darkBlue = Color.fromARGB(255, 18, 32, 47);

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData.dark().copyWith(
        scaffoldBackgroundColor: darkBlue,
      ),
      debugShowCheckedModeBanner: false,
      home: const MyWidget(),
    );
  }
}

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

  @override
  createState() => _MyWidgetState();
}

class _MyWidgetState extends State<MyWidget>
    with SingleTickerProviderStateMixin {
  int _value = 200;
  late AnimationController _yellowController;
  late Animation<double> animation;

  @override
  void initState() {
    super.initState();
    _yellowController = AnimationController(
      duration: Duration(milliseconds: _value),
      vsync: this,
    );
    _yellowController.repeat(reverse: true);
    animation = Tween<double>(begin: 0, end: 1).animate(_yellowController);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('AppBar Title'),
      ),
      body: Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            AnimatedBuilder(
              animation: animation,
              builder: (context, child) {
                return Transform.scale(
                  scale: animation.value,
                  child: child!,
                );
              },
              child: const SizedBox.square(
                dimension: 50,
                child: ColoredBox(
                  color: Colors.white,
                ),
              ),
            ),
            Slider(
              min: 200,
              max: 2000,
              activeColor: Colors.black54,
              inactiveColor: Colors.black12,
              thumbColor: Colors.black,
              value: _value.toDouble(),
              onChanged: (value) {
                _yellowController.duration = Duration(milliseconds: value.round());
                _yellowController.repeat(reverse: true);
                _value = value.round();
                setState(() {});
              },
            ),
          ],
        ),
      ),
    );
  }
}