| // 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 Offstage |
| |
| 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 MaterialApp( |
| title: _title, |
| home: Scaffold( |
| appBar: AppBar(title: const Text(_title)), |
| body: const Center( |
| child: MyStatefulWidget(), |
| ), |
| ), |
| ); |
| } |
| } |
| |
| class MyStatefulWidget extends StatefulWidget { |
| const MyStatefulWidget({super.key}); |
| |
| @override |
| State<MyStatefulWidget> createState() => _MyStatefulWidgetState(); |
| } |
| |
| class _MyStatefulWidgetState extends State<MyStatefulWidget> { |
| final GlobalKey _key = GlobalKey(); |
| bool _offstage = true; |
| |
| Size _getFlutterLogoSize() { |
| final RenderBox renderLogo = |
| _key.currentContext!.findRenderObject()! as RenderBox; |
| return renderLogo.size; |
| } |
| |
| @override |
| Widget build(BuildContext context) { |
| return Column( |
| mainAxisAlignment: MainAxisAlignment.center, |
| children: <Widget>[ |
| Offstage( |
| offstage: _offstage, |
| child: FlutterLogo( |
| key: _key, |
| size: 150.0, |
| ), |
| ), |
| Text('Flutter logo is offstage: $_offstage'), |
| ElevatedButton( |
| child: const Text('Toggle Offstage Value'), |
| onPressed: () { |
| setState(() { |
| _offstage = !_offstage; |
| }); |
| }, |
| ), |
| if (_offstage) |
| ElevatedButton( |
| child: const Text('Get Flutter Logo size'), |
| onPressed: () { |
| ScaffoldMessenger.of(context).showSnackBar( |
| SnackBar( |
| content: |
| Text('Flutter Logo size is ${_getFlutterLogoSize()}'), |
| ), |
| ); |
| }), |
| ], |
| ); |
| } |
| } |