flutter/examples/api/lib/widgets/transitions/align_transition.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.

// Flutter code sample for AlignTransition

import 'package:flutter/material.dart';

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

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

  static const String _title = 'Flutter Code Sample';

  @override
  Widget build(BuildContext context) {
    return const MaterialApp(
      title: _title,
      home: MyStatefulWidget(),
    );
  }
}

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

  @override
  State<MyStatefulWidget> createState() => _MyStatefulWidgetState();
}

/// AnimationControllers can be created with `vsync: this` because of TickerProviderStateMixin.
class _MyStatefulWidgetState extends State<MyStatefulWidget>
    with TickerProviderStateMixin {
// Using `late final` for [lazy initialization](https://dart.dev/null-safety/understanding-null-safety#lazy-initialization).
  late final AnimationController _controller = AnimationController(
    duration: const Duration(seconds: 2),
    vsync: this,
  )..repeat(reverse: true);
  late final Animation<AlignmentGeometry> _animation = Tween<AlignmentGeometry>(
    begin: Alignment.bottomLeft,
    end: Alignment.center,
  ).animate(
    CurvedAnimation(
      parent: _controller,
      curve: Curves.decelerate,
    ),
  );

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

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.white,
      child: AlignTransition(
        alignment: _animation,
        child: const Padding(
          padding: EdgeInsets.all(8),
          child: FlutterLogo(size: 150.0),
        ),
      ),
    );
  }
}