packages/flutter/lib/src/material/about.dart - mirrors/flutter - Git at Google

 // 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 'dart:async';
 import 'dart:developer' show Timeline, Flow;
 import 'dart:io' show Platform;

 import 'package:flutter/foundation.dart';
 import 'package:flutter/scheduler.dart';
 import 'package:flutter/widgets.dart' hide Flow;

 import 'app_bar.dart';
 import 'debug.dart';
 import 'dialog.dart';
 import 'flat_button.dart';
 import 'list_tile.dart';
 import 'material_localizations.dart';
 import 'page.dart';
 import 'progress_indicator.dart';
 import 'scaffold.dart';
 import 'scrollbar.dart';
 import 'theme.dart';

 /// A [ListTile] that shows an about box.
 ///
 /// This widget is often added to an app's [Drawer]. When tapped it shows
 /// an about box dialog with [showAboutDialog].
 ///
 /// The about box will include a button that shows licenses for software used by
 /// the application. The licenses shown are those returned by the
 /// [LicenseRegistry] API, which can be used to add more licenses to the list.
 ///
 /// If your application does not have a [Drawer], you should provide an
 /// affordance to call [showAboutDialog] or (at least) [showLicensePage].
 /// {@tool dartpad --template=stateless_widget_material}
 ///
 /// This sample shows two ways to open [AboutDialog]. The first one
 /// uses an [AboutListTile], and the second uses the [showAboutDialog] function.
 ///
 /// ```dart
 ///
 ///  Widget build(BuildContext context) {
 ///    final TextStyle textStyle = Theme.of(context).textTheme.bodyText2;
 ///    final List<Widget> aboutBoxChildren = <Widget>[
 ///      SizedBox(height: 24),
 ///      RichText(
 ///        text: TextSpan(
 ///          children: <TextSpan>[
 ///            TextSpan(
 ///              style: textStyle,
 ///              text: 'Flutter is Google’s UI toolkit for building beautiful, '
 ///              'natively compiled applications for mobile, web, and desktop '
 ///              'from a single codebase. Learn more about Flutter at '
 ///            ),
 ///            TextSpan(
 ///              style: textStyle.copyWith(color: Theme.of(context).accentColor),
 ///              text: 'https://flutter.dev'
 ///            ),
 ///            TextSpan(
 ///              style: textStyle,
 ///              text: '.'
 ///            ),
 ///          ],
 ///        ),
 ///      ),
 ///    ];
 ///
 ///    return Scaffold(
 ///      appBar: AppBar(
 ///        title: Text('Show About Example'),
 ///      ),
 ///      drawer: Drawer(
 ///        child: SingleChildScrollView(
 ///          child: SafeArea(
 ///            child: AboutListTile(
 ///              icon: Icon(Icons.info),
 ///              applicationIcon: FlutterLogo(),
 ///              applicationName: 'Show About Example',
 ///              applicationVersion: 'August 2019',
 ///              applicationLegalese: '© 2014 The Flutter Authors',
 ///              aboutBoxChildren: aboutBoxChildren,
 ///            ),
 ///          ),
 ///        ),
 ///      ),
 ///      body: Center(
 ///        child: RaisedButton(
 ///          child: Text('Show About Example'),
 ///          onPressed: () {
 ///            showAboutDialog(
 ///              context: context,
 ///              applicationIcon: FlutterLogo(),
 ///              applicationName: 'Show About Example',
 ///              applicationVersion: 'August 2019',
 ///              applicationLegalese: '© 2014 The Flutter Authors',
 ///              children: aboutBoxChildren,
 ///            );
 ///          },
 ///        ),
 ///      ),
 ///    );
 ///}
 /// ```
 /// {@end-tool}
 ///
 class AboutListTile extends StatelessWidget {
   /// Creates a list tile for showing an about box.
   ///
   /// The arguments are all optional. The application name, if omitted, will be
   /// derived from the nearest [Title] widget. The version, icon, and legalese
   /// values default to the empty string.
   const AboutListTile({
     Key key,
     this.icon,
     this.child,
     this.applicationName,
     this.applicationVersion,
     this.applicationIcon,
     this.applicationLegalese,
     this.aboutBoxChildren,
     this.dense,
   }) : super(key: key);

   /// The icon to show for this drawer item.
   ///
   /// By default no icon is shown.
   ///
   /// This is not necessarily the same as the image shown in the dialog box
   /// itself; which is controlled by the [applicationIcon] property.
   final Widget icon;

   /// The label to show on this drawer item.
   ///
   /// Defaults to a text widget that says "About Foo" where "Foo" is the
   /// application name specified by [applicationName].
   final Widget child;

   /// The name of the application.
   ///
   /// This string is used in the default label for this drawer item (see
   /// [child]) and as the caption of the [AboutDialog] that is shown.
   ///
   /// Defaults to the value of [Title.title], if a [Title] widget can be found.
   /// Otherwise, defaults to [Platform.resolvedExecutable].
   final String applicationName;

   /// The version of this build of the application.
   ///
   /// This string is shown under the application name in the [AboutDialog].
   ///
   /// Defaults to the empty string.
   final String applicationVersion;

   /// The icon to show next to the application name in the [AboutDialog].
   ///
   /// By default no icon is shown.
   ///
   /// Typically this will be an [ImageIcon] widget. It should honor the
   /// [IconTheme]'s [IconThemeData.size].
   ///
   /// This is not necessarily the same as the icon shown on the drawer item
   /// itself, which is controlled by the [icon] property.
   final Widget applicationIcon;

   /// A string to show in small print in the [AboutDialog].
   ///
   /// Typically this is a copyright notice.
   ///
   /// Defaults to the empty string.
   final String applicationLegalese;

   /// Widgets to add to the [AboutDialog] after the name, version, and legalese.
   ///
   /// This could include a link to a Web site, some descriptive text, credits,
   /// or other information to show in the about box.
   ///
   /// Defaults to nothing.
   final List<Widget> aboutBoxChildren;

   /// Whether this list tile is part of a vertically dense list.
   ///
   /// If this property is null, then its value is based on [ListTileTheme.dense].
   ///
   /// Dense list tiles default to a smaller height.
   final bool dense;

   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterial(context));
     assert(debugCheckHasMaterialLocalizations(context));
     return ListTile(
       leading: icon,
       title: child ?? Text(MaterialLocalizations.of(context).aboutListTileTitle(
         applicationName ?? _defaultApplicationName(context),
       )),
       dense: dense,
       onTap: () {
         showAboutDialog(
           context: context,
           applicationName: applicationName,
           applicationVersion: applicationVersion,
           applicationIcon: applicationIcon,
           applicationLegalese: applicationLegalese,
           children: aboutBoxChildren,
         );
       },
     );
   }
 }

 /// Displays an [AboutDialog], which describes the application and provides a
 /// button to show licenses for software used by the application.
 ///
 /// The arguments correspond to the properties on [AboutDialog].
 ///
 /// If the application has a [Drawer], consider using [AboutListTile] instead
 /// of calling this directly.
 ///
 /// If you do not need an about box in your application, you should at least
 /// provide an affordance to call [showLicensePage].
 ///
 /// The licenses shown on the [LicensePage] are those returned by the
 /// [LicenseRegistry] API, which can be used to add more licenses to the list.
 ///
 /// The [context], [useRootNavigator] and [routeSettings] arguments are passed to
 /// [showDialog], the documentation for which discusses how it is used.
 void showAboutDialog({
   @required BuildContext context,
   String applicationName,
   String applicationVersion,
   Widget applicationIcon,
   String applicationLegalese,
   List<Widget> children,
   bool useRootNavigator = true,
   RouteSettings routeSettings,
 }) {
   assert(context != null);
   assert(useRootNavigator != null);
   showDialog<void>(
     context: context,
     useRootNavigator: useRootNavigator,
     builder: (BuildContext context) {
       return AboutDialog(
         applicationName: applicationName,
         applicationVersion: applicationVersion,
         applicationIcon: applicationIcon,
         applicationLegalese: applicationLegalese,
         children: children,
       );
     },
     routeSettings: routeSettings,
   );
 }

 /// Displays a [LicensePage], which shows licenses for software used by the
 /// application.
 ///
 /// The application arguments correspond to the properties on [LicensePage].
 ///
 /// The `context` argument is used to look up the [Navigator] for the page.
 ///
 /// The `useRootNavigator` argument is used to determine whether to push the
 /// page to the [Navigator] furthest from or nearest to the given `context`. It
 /// is `false` by default.
 ///
 /// If the application has a [Drawer], consider using [AboutListTile] instead
 /// of calling this directly.
 ///
 /// The [AboutDialog] shown by [showAboutDialog] includes a button that calls
 /// [showLicensePage].
 ///
 /// The licenses shown on the [LicensePage] are those returned by the
 /// [LicenseRegistry] API, which can be used to add more licenses to the list.
 void showLicensePage({
   @required BuildContext context,
   String applicationName,
   String applicationVersion,
   Widget applicationIcon,
   String applicationLegalese,
   bool useRootNavigator = false,
 }) {
   assert(context != null);
   assert(useRootNavigator != null);
   Navigator.of(context, rootNavigator: useRootNavigator).push(MaterialPageRoute<void>(
     builder: (BuildContext context) => LicensePage(
       applicationName: applicationName,
       applicationVersion: applicationVersion,
       applicationIcon: applicationIcon,
       applicationLegalese: applicationLegalese,
     ),
   ));
 }

 /// An about box. This is a dialog box with the application's icon, name,
 /// version number, and copyright, plus a button to show licenses for software
 /// used by the application.
 ///
 /// To show an [AboutDialog], use [showAboutDialog].
 ///
 /// If the application has a [Drawer], the [AboutListTile] widget can make the
 /// process of showing an about dialog simpler.
 ///
 /// The [AboutDialog] shown by [showAboutDialog] includes a button that calls
 /// [showLicensePage].
 ///
 /// The licenses shown on the [LicensePage] are those returned by the
 /// [LicenseRegistry] API, which can be used to add more licenses to the list.
 class AboutDialog extends StatelessWidget {
   /// Creates an about box.
   ///
   /// The arguments are all optional. The application name, if omitted, will be
   /// derived from the nearest [Title] widget. The version, icon, and legalese
   /// values default to the empty string.
   const AboutDialog({
     Key key,
     this.applicationName,
     this.applicationVersion,
     this.applicationIcon,
     this.applicationLegalese,
     this.children,
   }) : super(key: key);

   /// The name of the application.
   ///
   /// Defaults to the value of [Title.title], if a [Title] widget can be found.
   /// Otherwise, defaults to [Platform.resolvedExecutable].
   final String applicationName;

   /// The version of this build of the application.
   ///
   /// This string is shown under the application name.
   ///
   /// Defaults to the empty string.
   final String applicationVersion;

   /// The icon to show next to the application name.
   ///
   /// By default no icon is shown.
   ///
   /// Typically this will be an [ImageIcon] widget. It should honor the
   /// [IconTheme]'s [IconThemeData.size].
   final Widget applicationIcon;

   /// A string to show in small print.
   ///
   /// Typically this is a copyright notice.
   ///
   /// Defaults to the empty string.
   final String applicationLegalese;

   /// Widgets to add to the dialog box after the name, version, and legalese.
   ///
   /// This could include a link to a Web site, some descriptive text, credits,
   /// or other information to show in the about box.
   ///
   /// Defaults to nothing.
   final List<Widget> children;

   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterialLocalizations(context));
     final String name = applicationName ?? _defaultApplicationName(context);
     final String version = applicationVersion ?? _defaultApplicationVersion(context);
     final Widget icon = applicationIcon ?? _defaultApplicationIcon(context);
     return AlertDialog(
       content: ListBody(
         children: <Widget>[
           Row(
             crossAxisAlignment: CrossAxisAlignment.start,
             children: <Widget>[
               if (icon != null) IconTheme(data: Theme.of(context).iconTheme, child: icon),
               Expanded(
                 child: Padding(
                   padding: const EdgeInsets.symmetric(horizontal: 24.0),
                   child: ListBody(
                     children: <Widget>[
                       Text(name, style: Theme.of(context).textTheme.headline5),
                       Text(version, style: Theme.of(context).textTheme.bodyText2),
                       Container(height: 18.0),
                       Text(applicationLegalese ?? '', style: Theme.of(context).textTheme.caption),
                     ],
                   ),
                 ),
               ),
             ],
           ),
           ...?children,
         ],
       ),
       actions: <Widget>[
         FlatButton(
           child: Text(MaterialLocalizations.of(context).viewLicensesButtonLabel),
           onPressed: () {
             showLicensePage(
               context: context,
               applicationName: applicationName,
               applicationVersion: applicationVersion,
               applicationIcon: applicationIcon,
               applicationLegalese: applicationLegalese,
             );
           },
         ),
         FlatButton(
           child: Text(MaterialLocalizations.of(context).closeButtonLabel),
           onPressed: () {
             Navigator.pop(context);
           },
         ),
       ],
       scrollable: true,
     );
   }
 }

 /// A page that shows licenses for software used by the application.
 ///
 /// To show a [LicensePage], use [showLicensePage].
 ///
 /// The [AboutDialog] shown by [showAboutDialog] and [AboutListTile] includes
 /// a button that calls [showLicensePage].
 ///
 /// The licenses shown on the [LicensePage] are those returned by the
 /// [LicenseRegistry] API, which can be used to add more licenses to the list.
 class LicensePage extends StatefulWidget {
   /// Creates a page that shows licenses for software used by the application.
   ///
   /// The arguments are all optional. The application name, if omitted, will be
   /// derived from the nearest [Title] widget. The version and legalese values
   /// default to the empty string.
   ///
   /// The licenses shown on the [LicensePage] are those returned by the
   /// [LicenseRegistry] API, which can be used to add more licenses to the list.
   const LicensePage({
     Key key,
     this.applicationName,
     this.applicationVersion,
     this.applicationIcon,
     this.applicationLegalese,
   }) : super(key: key);

   /// The name of the application.
   ///
   /// Defaults to the value of [Title.title], if a [Title] widget can be found.
   /// Otherwise, defaults to [Platform.resolvedExecutable].
   final String applicationName;

   /// The version of this build of the application.
   ///
   /// This string is shown under the application name.
   ///
   /// Defaults to the empty string.
   final String applicationVersion;

   /// The icon to show below the application name.
   ///
   /// By default no icon is shown.
   ///
   /// Typically this will be an [ImageIcon] widget. It should honor the
   /// [IconTheme]'s [IconThemeData.size].
   final Widget applicationIcon;

   /// A string to show in small print.
   ///
   /// Typically this is a copyright notice.
   ///
   /// Defaults to the empty string.
   final String applicationLegalese;

   @override
   _LicensePageState createState() => _LicensePageState();
 }

 class _LicensePageState extends State<LicensePage> {
   @override
   void initState() {
     super.initState();
     _initLicenses();
   }

   final List<Widget> _licenses = <Widget>[];
   bool _loaded = false;

   Future<void> _initLicenses() async {
     int debugFlowId = -1;
     assert(() {
       final Flow flow = Flow.begin();
       Timeline.timeSync('_initLicenses()', () { }, flow: flow);
       debugFlowId = flow.id;
       return true;
     }());
     await for (final LicenseEntry license in LicenseRegistry.licenses) {
       if (!mounted) {
         return;
       }
       assert(() {
         Timeline.timeSync('_initLicenses()', () { }, flow: Flow.step(debugFlowId));
         return true;
       }());
       final List<LicenseParagraph> paragraphs =
         await SchedulerBinding.instance.scheduleTask<List<LicenseParagraph>>(
           license.paragraphs.toList,
           Priority.animation,
           debugLabel: 'License',
         );
       if (!mounted) {
         return;
       }
       setState(() {
         _licenses.add(const Padding(
           padding: EdgeInsets.symmetric(vertical: 18.0),
           child: Text(
             '🍀‬', // That's U+1F340. Could also use U+2766 (❦) if U+1F340 doesn't work everywhere.
             textAlign: TextAlign.center,
           ),
         ));
         _licenses.add(Container(
           decoration: const BoxDecoration(
             border: Border(bottom: BorderSide(width: 0.0))
           ),
           child: Text(
             license.packages.join(', '),
             style: const TextStyle(fontWeight: FontWeight.bold),
             textAlign: TextAlign.center,
           ),
         ));
         for (final LicenseParagraph paragraph in paragraphs) {
           if (paragraph.indent == LicenseParagraph.centeredIndent) {
             _licenses.add(Padding(
               padding: const EdgeInsets.only(top: 16.0),
               child: Text(
                 paragraph.text,
                 style: const TextStyle(fontWeight: FontWeight.bold),
                 textAlign: TextAlign.center,
               ),
             ));
           } else {
             assert(paragraph.indent >= 0);
             _licenses.add(Padding(
               padding: EdgeInsetsDirectional.only(top: 8.0, start: 16.0 * paragraph.indent),
               child: Text(paragraph.text),
             ));
           }
         }
       });
     }
     setState(() {
       _loaded = true;
     });
     assert(() {
       Timeline.timeSync('Build scheduled', () { }, flow: Flow.end(debugFlowId));
       return true;
     }());
   }

   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterialLocalizations(context));
     final String name = widget.applicationName ?? _defaultApplicationName(context);
     final String version = widget.applicationVersion ?? _defaultApplicationVersion(context);
     final Widget icon = widget.applicationIcon ?? _defaultApplicationIcon(context);
     final MaterialLocalizations localizations = MaterialLocalizations.of(context);
     return Scaffold(
       appBar: AppBar(
         title: Text(localizations.licensesPageTitle),
       ),
       // All of the licenses page text is English. We don't want localized text
       // or text direction.
       body: Localizations.override(
         locale: const Locale('en', 'US'),
         context: context,
         child: DefaultTextStyle(
           style: Theme.of(context).textTheme.caption,
           child: SafeArea(
             bottom: false,
             child: Scrollbar(
               child: ListView(
                 padding: const EdgeInsets.symmetric(horizontal: 8.0, vertical: 12.0),
                 children: <Widget>[
                   Text(name, style: Theme.of(context).textTheme.headline5, textAlign: TextAlign.center),
                   if (icon != null) IconTheme(data: Theme.of(context).iconTheme, child: icon),
                   Text(version, style: Theme.of(context).textTheme.bodyText2, textAlign: TextAlign.center),
                   Container(height: 18.0),
                   Text(widget.applicationLegalese ?? '', style: Theme.of(context).textTheme.caption, textAlign: TextAlign.center),
                   Container(height: 18.0),
                   Text('Powered by Flutter', style: Theme.of(context).textTheme.bodyText2, textAlign: TextAlign.center),
                   Container(height: 24.0),
                   ..._licenses,
                   if (!_loaded)
                     const Padding(
                       padding: EdgeInsets.symmetric(vertical: 24.0),
                       child: Center(
                         child: CircularProgressIndicator(),
                       ),
                     ),
                 ],
               ),
             ),
           ),
         ),
       ),
     );
   }
 }

 String _defaultApplicationName(BuildContext context) {
   // This doesn't handle the case of the application's title dynamically
   // changing. In theory, we should make Title expose the current application
   // title using an InheritedWidget, and so forth. However, in practice, if
   // someone really wants their application title to change dynamically, they
   // can provide an explicit applicationName to the widgets defined in this
   // file, instead of relying on the default.
   final Title ancestorTitle = context.findAncestorWidgetOfExactType<Title>();
   return ancestorTitle?.title ?? Platform.resolvedExecutable.split(Platform.pathSeparator).last;
 }

 String _defaultApplicationVersion(BuildContext context) {
   // TODO(ianh): Get this from the embedder somehow.
   return '';
 }

 Widget _defaultApplicationIcon(BuildContext context) {
   // TODO(ianh): Get this from the embedder somehow.
   return null;
 }
	// 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 'dart:async';
	import 'dart:developer' show Timeline, Flow;
	import 'dart:io' show Platform;

	import 'package:flutter/foundation.dart';
	import 'package:flutter/scheduler.dart';
	import 'package:flutter/widgets.dart' hide Flow;

	import 'app_bar.dart';
	import 'debug.dart';
	import 'dialog.dart';
	import 'flat_button.dart';
	import 'list_tile.dart';
	import 'material_localizations.dart';
	import 'page.dart';
	import 'progress_indicator.dart';
	import 'scaffold.dart';
	import 'scrollbar.dart';
	import 'theme.dart';

	/// A [ListTile] that shows an about box.
	///
	/// This widget is often added to an app's [Drawer]. When tapped it shows
	/// an about box dialog with [showAboutDialog].
	///
	/// The about box will include a button that shows licenses for software used by
	/// the application. The licenses shown are those returned by the
	/// [LicenseRegistry] API, which can be used to add more licenses to the list.
	///
	/// If your application does not have a [Drawer], you should provide an
	/// affordance to call [showAboutDialog] or (at least) [showLicensePage].
	/// {@tool dartpad --template=stateless_widget_material}
	///
	/// This sample shows two ways to open [AboutDialog]. The first one
	/// uses an [AboutListTile], and the second uses the [showAboutDialog] function.
	///
	/// ```dart
	///
	/// Widget build(BuildContext context) {
	/// final TextStyle textStyle = Theme.of(context).textTheme.bodyText2;
	/// final List<Widget> aboutBoxChildren = <Widget>[
	/// SizedBox(height: 24),
	/// RichText(
	/// text: TextSpan(
	/// children: <TextSpan>[
	/// TextSpan(
	/// style: textStyle,
	/// text: 'Flutter is Google’s UI toolkit for building beautiful, '
	/// 'natively compiled applications for mobile, web, and desktop '
	/// 'from a single codebase. Learn more about Flutter at '
	/// ),
	/// TextSpan(
	/// style: textStyle.copyWith(color: Theme.of(context).accentColor),
	/// text: 'https://flutter.dev'
	/// ),
	/// TextSpan(
	/// style: textStyle,
	/// text: '.'
	/// ),
	/// ],
	/// ),
	/// ),
	/// ];
	///
	/// return Scaffold(
	/// appBar: AppBar(
	/// title: Text('Show About Example'),
	/// ),
	/// drawer: Drawer(
	/// child: SingleChildScrollView(
	/// child: SafeArea(
	/// child: AboutListTile(
	/// icon: Icon(Icons.info),
	/// applicationIcon: FlutterLogo(),
	/// applicationName: 'Show About Example',
	/// applicationVersion: 'August 2019',
	/// applicationLegalese: '© 2014 The Flutter Authors',
	/// aboutBoxChildren: aboutBoxChildren,
	/// ),
	/// ),
	/// ),
	/// ),
	/// body: Center(
	/// child: RaisedButton(
	/// child: Text('Show About Example'),
	/// onPressed: () {
	/// showAboutDialog(
	/// context: context,
	/// applicationIcon: FlutterLogo(),
	/// applicationName: 'Show About Example',
	/// applicationVersion: 'August 2019',
	/// applicationLegalese: '© 2014 The Flutter Authors',
	/// children: aboutBoxChildren,
	/// );
	/// },
	/// ),
	/// ),
	/// );
	///}
	/// ```
	/// {@end-tool}
	///
	class AboutListTile extends StatelessWidget {
	/// Creates a list tile for showing an about box.
	///
	/// The arguments are all optional. The application name, if omitted, will be
	/// derived from the nearest [Title] widget. The version, icon, and legalese
	/// values default to the empty string.
	const AboutListTile({
	Key key,
	this.icon,
	this.child,
	this.applicationName,
	this.applicationVersion,
	this.applicationIcon,
	this.applicationLegalese,
	this.aboutBoxChildren,
	this.dense,
	}) : super(key: key);

	/// The icon to show for this drawer item.
	///
	/// By default no icon is shown.
	///
	/// This is not necessarily the same as the image shown in the dialog box
	/// itself; which is controlled by the [applicationIcon] property.
	final Widget icon;

	/// The label to show on this drawer item.
	///
	/// Defaults to a text widget that says "About Foo" where "Foo" is the
	/// application name specified by [applicationName].
	final Widget child;

	/// The name of the application.
	///
	/// This string is used in the default label for this drawer item (see
	/// [child]) and as the caption of the [AboutDialog] that is shown.
	///
	/// Defaults to the value of [Title.title], if a [Title] widget can be found.
	/// Otherwise, defaults to [Platform.resolvedExecutable].
	final String applicationName;

	/// The version of this build of the application.
	///
	/// This string is shown under the application name in the [AboutDialog].
	///
	/// Defaults to the empty string.
	final String applicationVersion;

	/// The icon to show next to the application name in the [AboutDialog].
	///
	/// By default no icon is shown.
	///
	/// Typically this will be an [ImageIcon] widget. It should honor the
	/// [IconTheme]'s [IconThemeData.size].
	///
	/// This is not necessarily the same as the icon shown on the drawer item
	/// itself, which is controlled by the [icon] property.
	final Widget applicationIcon;

	/// A string to show in small print in the [AboutDialog].
	///
	/// Typically this is a copyright notice.
	///
	/// Defaults to the empty string.
	final String applicationLegalese;

	/// Widgets to add to the [AboutDialog] after the name, version, and legalese.
	///
	/// This could include a link to a Web site, some descriptive text, credits,
	/// or other information to show in the about box.
	///
	/// Defaults to nothing.
	final List<Widget> aboutBoxChildren;

	/// Whether this list tile is part of a vertically dense list.
	///
	/// If this property is null, then its value is based on [ListTileTheme.dense].
	///
	/// Dense list tiles default to a smaller height.
	final bool dense;

	@override
	Widget build(BuildContext context) {
	assert(debugCheckHasMaterial(context));
	assert(debugCheckHasMaterialLocalizations(context));
	return ListTile(
	leading: icon,
	title: child ?? Text(MaterialLocalizations.of(context).aboutListTileTitle(
	applicationName ?? _defaultApplicationName(context),
	)),
	dense: dense,
	onTap: () {
	showAboutDialog(
	context: context,
	applicationName: applicationName,
	applicationVersion: applicationVersion,
	applicationIcon: applicationIcon,
	applicationLegalese: applicationLegalese,
	children: aboutBoxChildren,
	);
	},
	);
	}
	}

	/// Displays an [AboutDialog], which describes the application and provides a
	/// button to show licenses for software used by the application.
	///
	/// The arguments correspond to the properties on [AboutDialog].
	///
	/// If the application has a [Drawer], consider using [AboutListTile] instead
	/// of calling this directly.
	///
	/// If you do not need an about box in your application, you should at least
	/// provide an affordance to call [showLicensePage].
	///
	/// The licenses shown on the [LicensePage] are those returned by the
	/// [LicenseRegistry] API, which can be used to add more licenses to the list.
	///
	/// The [context], [useRootNavigator] and [routeSettings] arguments are passed to
	/// [showDialog], the documentation for which discusses how it is used.
	void showAboutDialog({
	@required BuildContext context,
	String applicationName,
	String applicationVersion,
	Widget applicationIcon,
	String applicationLegalese,
	List<Widget> children,
	bool useRootNavigator = true,
	RouteSettings routeSettings,
	}) {
	assert(context != null);
	assert(useRootNavigator != null);
	showDialog<void>(
	context: context,
	useRootNavigator: useRootNavigator,
	builder: (BuildContext context) {
	return AboutDialog(
	applicationName: applicationName,
	applicationVersion: applicationVersion,
	applicationIcon: applicationIcon,
	applicationLegalese: applicationLegalese,
	children: children,
	);
	},
	routeSettings: routeSettings,
	);
	}

	/// Displays a [LicensePage], which shows licenses for software used by the
	/// application.
	///
	/// The application arguments correspond to the properties on [LicensePage].
	///
	/// The `context` argument is used to look up the [Navigator] for the page.
	///
	/// The `useRootNavigator` argument is used to determine whether to push the
	/// page to the [Navigator] furthest from or nearest to the given `context`. It
	/// is `false` by default.
	///
	/// If the application has a [Drawer], consider using [AboutListTile] instead
	/// of calling this directly.
	///
	/// The [AboutDialog] shown by [showAboutDialog] includes a button that calls
	/// [showLicensePage].
	///
	/// The licenses shown on the [LicensePage] are those returned by the
	/// [LicenseRegistry] API, which can be used to add more licenses to the list.
	void showLicensePage({
	@required BuildContext context,
	String applicationName,
	String applicationVersion,
	Widget applicationIcon,
	String applicationLegalese,
	bool useRootNavigator = false,
	}) {
	assert(context != null);
	assert(useRootNavigator != null);
	Navigator.of(context, rootNavigator: useRootNavigator).push(MaterialPageRoute<void>(
	builder: (BuildContext context) => LicensePage(
	applicationName: applicationName,
	applicationVersion: applicationVersion,
	applicationIcon: applicationIcon,
	applicationLegalese: applicationLegalese,
	),
	));
	}

	/// An about box. This is a dialog box with the application's icon, name,
	/// version number, and copyright, plus a button to show licenses for software
	/// used by the application.
	///
	/// To show an [AboutDialog], use [showAboutDialog].
	///
	/// If the application has a [Drawer], the [AboutListTile] widget can make the
	/// process of showing an about dialog simpler.
	///
	/// The [AboutDialog] shown by [showAboutDialog] includes a button that calls
	/// [showLicensePage].
	///
	/// The licenses shown on the [LicensePage] are those returned by the
	/// [LicenseRegistry] API, which can be used to add more licenses to the list.
	class AboutDialog extends StatelessWidget {
	/// Creates an about box.
	///
	/// The arguments are all optional. The application name, if omitted, will be
	/// derived from the nearest [Title] widget. The version, icon, and legalese
	/// values default to the empty string.
	const AboutDialog({
	Key key,
	this.applicationName,
	this.applicationVersion,
	this.applicationIcon,
	this.applicationLegalese,
	this.children,
	}) : super(key: key);

	/// The name of the application.
	///
	/// Defaults to the value of [Title.title], if a [Title] widget can be found.
	/// Otherwise, defaults to [Platform.resolvedExecutable].
	final String applicationName;

	/// The version of this build of the application.
	///
	/// This string is shown under the application name.
	///
	/// Defaults to the empty string.
	final String applicationVersion;

	/// The icon to show next to the application name.
	///
	/// By default no icon is shown.
	///
	/// Typically this will be an [ImageIcon] widget. It should honor the
	/// [IconTheme]'s [IconThemeData.size].
	final Widget applicationIcon;

	/// A string to show in small print.
	///
	/// Typically this is a copyright notice.
	///
	/// Defaults to the empty string.
	final String applicationLegalese;

	/// Widgets to add to the dialog box after the name, version, and legalese.
	///
	/// This could include a link to a Web site, some descriptive text, credits,
	/// or other information to show in the about box.
	///
	/// Defaults to nothing.
	final List<Widget> children;

	@override
	Widget build(BuildContext context) {
	assert(debugCheckHasMaterialLocalizations(context));
	final String name = applicationName ?? _defaultApplicationName(context);
	final String version = applicationVersion ?? _defaultApplicationVersion(context);
	final Widget icon = applicationIcon ?? _defaultApplicationIcon(context);
	return AlertDialog(
	content: ListBody(
	children: <Widget>[
	Row(
	crossAxisAlignment: CrossAxisAlignment.start,
	children: <Widget>[
	if (icon != null) IconTheme(data: Theme.of(context).iconTheme, child: icon),
	Expanded(
	child: Padding(
	padding: const EdgeInsets.symmetric(horizontal: 24.0),
	child: ListBody(
	children: <Widget>[
	Text(name, style: Theme.of(context).textTheme.headline5),
	Text(version, style: Theme.of(context).textTheme.bodyText2),
	Container(height: 18.0),
	Text(applicationLegalese ?? '', style: Theme.of(context).textTheme.caption),
	],
	),
	),
	),
	],
	),
	...?children,
	],
	),
	actions: <Widget>[
	FlatButton(
	child: Text(MaterialLocalizations.of(context).viewLicensesButtonLabel),
	onPressed: () {
	showLicensePage(
	context: context,
	applicationName: applicationName,
	applicationVersion: applicationVersion,
	applicationIcon: applicationIcon,
	applicationLegalese: applicationLegalese,
	);
	},
	),
	FlatButton(
	child: Text(MaterialLocalizations.of(context).closeButtonLabel),
	onPressed: () {
	Navigator.pop(context);
	},
	),
	],
	scrollable: true,
	);
	}
	}

	/// A page that shows licenses for software used by the application.
	///
	/// To show a [LicensePage], use [showLicensePage].
	///
	/// The [AboutDialog] shown by [showAboutDialog] and [AboutListTile] includes
	/// a button that calls [showLicensePage].
	///
	/// The licenses shown on the [LicensePage] are those returned by the
	/// [LicenseRegistry] API, which can be used to add more licenses to the list.
	class LicensePage extends StatefulWidget {
	/// Creates a page that shows licenses for software used by the application.
	///
	/// The arguments are all optional. The application name, if omitted, will be
	/// derived from the nearest [Title] widget. The version and legalese values
	/// default to the empty string.
	///
	/// The licenses shown on the [LicensePage] are those returned by the
	/// [LicenseRegistry] API, which can be used to add more licenses to the list.
	const LicensePage({
	Key key,
	this.applicationName,
	this.applicationVersion,
	this.applicationIcon,
	this.applicationLegalese,
	}) : super(key: key);

	/// The name of the application.
	///
	/// Defaults to the value of [Title.title], if a [Title] widget can be found.
	/// Otherwise, defaults to [Platform.resolvedExecutable].
	final String applicationName;

	/// The version of this build of the application.
	///
	/// This string is shown under the application name.
	///
	/// Defaults to the empty string.
	final String applicationVersion;

	/// The icon to show below the application name.
	///
	/// By default no icon is shown.
	///
	/// Typically this will be an [ImageIcon] widget. It should honor the
	/// [IconTheme]'s [IconThemeData.size].
	final Widget applicationIcon;

	/// A string to show in small print.
	///
	/// Typically this is a copyright notice.
	///
	/// Defaults to the empty string.
	final String applicationLegalese;

	@override
	_LicensePageState createState() => _LicensePageState();
	}

	class _LicensePageState extends State<LicensePage> {
	@override
	void initState() {
	super.initState();
	_initLicenses();
	}

	final List<Widget> _licenses = <Widget>[];
	bool _loaded = false;

	Future<void> _initLicenses() async {
	int debugFlowId = -1;
	assert(() {
	final Flow flow = Flow.begin();
	Timeline.timeSync('_initLicenses()', () { }, flow: flow);
	debugFlowId = flow.id;
	return true;
	}());
	await for (final LicenseEntry license in LicenseRegistry.licenses) {
	if (!mounted) {
	return;
	}
	assert(() {
	Timeline.timeSync('_initLicenses()', () { }, flow: Flow.step(debugFlowId));
	return true;
	}());
	final List<LicenseParagraph> paragraphs =
	await SchedulerBinding.instance.scheduleTask<List<LicenseParagraph>>(
	license.paragraphs.toList,
	Priority.animation,
	debugLabel: 'License',
	);
	if (!mounted) {
	return;
	}
	setState(() {
	_licenses.add(const Padding(
	padding: EdgeInsets.symmetric(vertical: 18.0),
	child: Text(
	'🍀‬', // That's U+1F340. Could also use U+2766 (❦) if U+1F340 doesn't work everywhere.
	textAlign: TextAlign.center,
	),
	));
	_licenses.add(Container(
	decoration: const BoxDecoration(
	border: Border(bottom: BorderSide(width: 0.0))
	),
	child: Text(
	license.packages.join(', '),
	style: const TextStyle(fontWeight: FontWeight.bold),
	textAlign: TextAlign.center,
	),
	));
	for (final LicenseParagraph paragraph in paragraphs) {
	if (paragraph.indent == LicenseParagraph.centeredIndent) {
	_licenses.add(Padding(
	padding: const EdgeInsets.only(top: 16.0),
	child: Text(
	paragraph.text,
	style: const TextStyle(fontWeight: FontWeight.bold),
	textAlign: TextAlign.center,
	),
	));
	} else {
	assert(paragraph.indent >= 0);
	_licenses.add(Padding(
	padding: EdgeInsetsDirectional.only(top: 8.0, start: 16.0 * paragraph.indent),
	child: Text(paragraph.text),
	));
	}
	}
	});
	}
	setState(() {
	_loaded = true;
	});
	assert(() {
	Timeline.timeSync('Build scheduled', () { }, flow: Flow.end(debugFlowId));
	return true;
	}());
	}

	@override
	Widget build(BuildContext context) {
	assert(debugCheckHasMaterialLocalizations(context));
	final String name = widget.applicationName ?? _defaultApplicationName(context);
	final String version = widget.applicationVersion ?? _defaultApplicationVersion(context);
	final Widget icon = widget.applicationIcon ?? _defaultApplicationIcon(context);
	final MaterialLocalizations localizations = MaterialLocalizations.of(context);
	return Scaffold(
	appBar: AppBar(
	title: Text(localizations.licensesPageTitle),
	),
	// All of the licenses page text is English. We don't want localized text
	// or text direction.
	body: Localizations.override(
	locale: const Locale('en', 'US'),
	context: context,
	child: DefaultTextStyle(
	style: Theme.of(context).textTheme.caption,
	child: SafeArea(
	bottom: false,
	child: Scrollbar(
	child: ListView(
	padding: const EdgeInsets.symmetric(horizontal: 8.0, vertical: 12.0),
	children: <Widget>[
	Text(name, style: Theme.of(context).textTheme.headline5, textAlign: TextAlign.center),
	if (icon != null) IconTheme(data: Theme.of(context).iconTheme, child: icon),
	Text(version, style: Theme.of(context).textTheme.bodyText2, textAlign: TextAlign.center),
	Container(height: 18.0),
	Text(widget.applicationLegalese ?? '', style: Theme.of(context).textTheme.caption, textAlign: TextAlign.center),
	Container(height: 18.0),
	Text('Powered by Flutter', style: Theme.of(context).textTheme.bodyText2, textAlign: TextAlign.center),
	Container(height: 24.0),
	..._licenses,
	if (!_loaded)
	const Padding(
	padding: EdgeInsets.symmetric(vertical: 24.0),
	child: Center(
	child: CircularProgressIndicator(),
	),
	),
	],
	),
	),
	),
	),
	),
	);
	}
	}

	String _defaultApplicationName(BuildContext context) {
	// This doesn't handle the case of the application's title dynamically
	// changing. In theory, we should make Title expose the current application
	// title using an InheritedWidget, and so forth. However, in practice, if
	// someone really wants their application title to change dynamically, they
	// can provide an explicit applicationName to the widgets defined in this
	// file, instead of relying on the default.
	final Title ancestorTitle = context.findAncestorWidgetOfExactType<Title>();
	return ancestorTitle?.title ?? Platform.resolvedExecutable.split(Platform.pathSeparator).last;
	}

	String _defaultApplicationVersion(BuildContext context) {
	// TODO(ianh): Get this from the embedder somehow.
	return '';
	}

	Widget _defaultApplicationIcon(BuildContext context) {
	// TODO(ianh): Get this from the embedder somehow.
	return null;
	}