examples/api/lib/widgets/transitions/positioned_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.

import 'package:flutter/material.dart';

/// Flutter code sample for [PositionedTransition].

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

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

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

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

  @override
  State<PositionedTransitionExample> createState() => _PositionedTransitionExampleState();
}

/// [AnimationController]s can be created with `vsync: this` because of
/// [TickerProviderStateMixin].
class _PositionedTransitionExampleState extends State<PositionedTransitionExample>
    with TickerProviderStateMixin {
  late final AnimationController _controller = AnimationController(
    duration: const Duration(seconds: 2),
    vsync: this,
  )..repeat(reverse: true);

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

  @override
  Widget build(BuildContext context) {
    const double smallLogo = 100;
    const double bigLogo = 200;

    return LayoutBuilder(
      builder: (BuildContext context, BoxConstraints constraints) {
        final Size biggest = constraints.biggest;
        return Stack(
          children: <Widget>[
            PositionedTransition(
              rect: RelativeRectTween(
                begin: RelativeRect.fromSize(
                  const Rect.fromLTWH(0, 0, smallLogo, smallLogo),
                  biggest,
                ),
                end: RelativeRect.fromSize(
                  Rect.fromLTWH(
                    biggest.width - bigLogo,
                    biggest.height - bigLogo,
                    bigLogo,
                    bigLogo,
                  ),
                  biggest,
                ),
              ).animate(CurvedAnimation(parent: _controller, curve: Curves.elasticInOut)),
              child: const Padding(padding: EdgeInsets.all(8), child: FlutterLogo()),
            ),
          ],
        );
      },
    );
  }
}