examples/api/lib/widgets/animated_switcher/animated_switcher.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.

// Template: dev/snippets/config/templates/stateful_widget_material.tmpl
//
// Comment lines marked with "▼▼▼" and "▲▲▲" are used for authoring
// of samples, and may be ignored if you are just exploring the sample.

// Flutter code sample for AnimatedSwitcher
//
//***************************************************************************
//* ▼▼▼▼▼▼▼▼ description ▼▼▼▼▼▼▼▼ (do not modify or remove section marker)

// This sample shows a counter that animates the scale of a text widget
// whenever the value changes.

//* ▲▲▲▲▲▲▲▲ description ▲▲▲▲▲▲▲▲ (do not modify or remove section marker)
//***************************************************************************

import 'package:flutter/material.dart';

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

/// This is the main application widget.
class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  static const String _title = 'Flutter Code Sample';

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

/// This is the stateful widget that the main application instantiates.
class MyStatefulWidget extends StatefulWidget {
  const MyStatefulWidget({Key? key}) : super(key: key);

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

/// This is the private State class that goes with MyStatefulWidget.
class _MyStatefulWidgetState extends State<MyStatefulWidget> {
//********************************************************************
//* ▼▼▼▼▼▼▼▼ code ▼▼▼▼▼▼▼▼ (do not modify or remove section marker)

  int _count = 0;

  @override
  Widget build(BuildContext context) {
    return Container(
      color: Colors.white,
      child: Column(
        mainAxisAlignment: MainAxisAlignment.center,
        children: <Widget>[
          AnimatedSwitcher(
            duration: const Duration(milliseconds: 500),
            transitionBuilder: (Widget child, Animation<double> animation) {
              return ScaleTransition(child: child, scale: animation);
            },
            child: Text(
              '$_count',
              // This key causes the AnimatedSwitcher to interpret this as a "new"
              // child each time the count changes, so that it will begin its animation
              // when the count changes.
              key: ValueKey<int>(_count),
              style: Theme.of(context).textTheme.headline4,
            ),
          ),
          ElevatedButton(
            child: const Text('Increment'),
            onPressed: () {
              setState(() {
                _count += 1;
              });
            },
          ),
        ],
      ),
    );
  }

//* ▲▲▲▲▲▲▲▲ code ▲▲▲▲▲▲▲▲ (do not modify or remove section marker)
//********************************************************************

}