examples/api/lib/material/navigation_rail/navigation_rail.extended_animation.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/stateless_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 NavigationRail.extendedAnimation
//
//***************************************************************************
//* ▼▼▼▼▼▼▼▼ description ▼▼▼▼▼▼▼▼ (do not modify or remove section marker)

// This example shows how to use this animation to create a
// [FloatingActionButton] that animates itself between the normal and
// extended states of the [NavigationRail].
//
// An instance of `ExtendableFab` would be created for
// [NavigationRail.leading].

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

//********************************************************************************
//* ▼▼▼▼▼▼▼▼ code-dartImports ▼▼▼▼▼▼▼▼ (do not modify or remove section marker)

import 'dart:ui';

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//********************************************************************************

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: MyStatelessWidget(),
    );
  }
}

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

  @override
//********************************************************************
//* ▼▼▼▼▼▼▼▼ code ▼▼▼▼▼▼▼▼ (do not modify or remove section marker)

  Widget build(BuildContext context) {
    final Animation<double> animation =
        NavigationRail.extendedAnimation(context);
    return AnimatedBuilder(
      animation: animation,
      builder: (BuildContext context, Widget? child) {
        // The extended fab has a shorter height than the regular fab.
        return Container(
          height: 56,
          padding: EdgeInsets.symmetric(
            vertical: lerpDouble(0, 6, animation.value)!,
          ),
          child: animation.value == 0
              ? FloatingActionButton(
                  child: const Icon(Icons.add),
                  onPressed: () {},
                )
              : Align(
                  alignment: AlignmentDirectional.centerStart,
                  widthFactor: animation.value,
                  child: Padding(
                    padding: const EdgeInsetsDirectional.only(start: 8),
                    child: FloatingActionButton.extended(
                      icon: const Icon(Icons.add),
                      label: const Text('CREATE'),
                      onPressed: () {},
                    ),
                  ),
                ),
        );
      },
    );
  }

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

}