flutter/examples/api/lib/widgets/transitions/animated_widget.0.dart

// Copyright 2014 The Flutter Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'dart:math' as math;

import 'package:flutter/material.dart';

/// Flutter code sample for [AnimatedWidget].

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

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

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

class SpinningContainer extends AnimatedWidget {
  const SpinningContainer({super.key, required AnimationController controller})
    : super(listenable: controller);

  Animation<double> get _progress => listenable as Animation<double>;

  @override
  Widget build(BuildContext context) {
    return Transform.rotate(
      angle: _progress.value * 2.0 * math.pi,
      child: Container(width: 200.0, height: 200.0, color: Colors.green),
    );
  }
}

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

  @override
  State<AnimatedWidgetExample> createState() => _AnimatedWidgetExampleState();
}

/// [AnimationController]s can be created with `vsync: this` because of
/// [TickerProviderStateMixin].
class _AnimatedWidgetExampleState extends State<AnimatedWidgetExample>
    with TickerProviderStateMixin {
  late final AnimationController _controller = AnimationController(
    duration: const Duration(seconds: 10),
    vsync: this,
  )..repeat();

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

  @override
  Widget build(BuildContext context) {
    return SpinningContainer(controller: _controller);
  }
}