flutter/examples/api/lib/widgets/transitions/animated_builder.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 [AnimatedBuilder].

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

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

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

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

  @override
  State<AnimatedBuilderExample> createState() => _AnimatedBuilderExampleState();
}

/// AnimationControllers can be created with `vsync: this` because of
/// TickerProviderStateMixin.
class _AnimatedBuilderExampleState extends State<AnimatedBuilderExample>
    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 AnimatedBuilder(
      animation: _controller,
      child: Container(
        width: 200.0,
        height: 200.0,
        color: Colors.green,
        child: const Center(child: Text('Whee!')),
      ),
      builder: (BuildContext context, Widget? child) {
        return Transform.rotate(angle: _controller.value * 2.0 * math.pi, child: child);
      },
    );
  }
}