animation_controller.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 MaterialApp(
      title: 'AnimationController Example',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(),
    );
  }
}

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

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> with SingleTickerProviderStateMixin {
  late AnimationController _controller;
  late Animation<double> _animation;

  @override
  void initState() {
    super.initState();
    _controller = AnimationController(
       vsync: this, // requires a TickerProvider
      duration: const Duration(seconds: 2),
    );

    _animation = Tween<double>(begin: 100, end: 200).animate(_controller)
      ..addListener(() {
        setState(() {
          // The state that has changed here is managed by _animation
        });
      });
  }

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

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('AnimationController Example'),
      ),
      body: Column(
        children: <Widget>[
          Row(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              ElevatedButton(
                onPressed: () {
                  _controller.forward();
                },
                child: const Text('Forward'),
              ),
              const SizedBox(width: 10),
              ElevatedButton(
                onPressed: () {
                  _controller.reverse();
                },
                child: const Text('Reverse'),
              ),
              const SizedBox(width: 10),
              ElevatedButton(
                onPressed: () {
                  if (_controller.isAnimating) {
                    _controller.stop();
                  } else {
                    _controller.repeat();
                  }
                },
                child: const Text('Repeat/Stop'),
              ),
            ],
          ),
          Expanded(
            child: Center(
              child: Container(
                width: _animation.value,
                height: _animation.value,
                color: Colors.red,
              ),
            ),
          ),
        ],
      ),
    );
  }
}