animated_builder.0.dart 1.66 KB
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// 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';

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/// Flutter code sample for [AnimatedBuilder].
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void main() => runApp(const AnimatedBuilderExampleApp());
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class AnimatedBuilderExampleApp extends StatelessWidget {
  const AnimatedBuilderExampleApp({super.key});
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  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
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      home: AnimatedBuilderExample(),
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    );
  }
}

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class AnimatedBuilderExample extends StatefulWidget {
  const AnimatedBuilderExample({super.key});
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  @override
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  State<AnimatedBuilderExample> createState() => _AnimatedBuilderExampleState();
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}

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/// AnimationControllers can be created with `vsync: this` because of
/// TickerProviderStateMixin.
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class _AnimatedBuilderExampleState extends State<AnimatedBuilderExample> with TickerProviderStateMixin {
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  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,
        );
      },
    );
  }
}