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

 // Copyright 2016 The Chromium 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:io' show Platform;

 import 'package:flutter/widgets.dart';
 import 'package:flutter/foundation.dart';

 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].
 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: const Icon(null),
     this.child,
     this.applicationName,
     this.applicationVersion,
     this.applicationIcon,
     this.applicationLegalese,
     this.aboutBoxChildren
   }) : 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;

   @override
   Widget build(BuildContext context) {
     assert(debugCheckHasMaterial(context));
     return new ListTile(
       leading: icon,
       title: child ??
         new Text(MaterialLocalizations.of(context).aboutListTileTitle(applicationName ?? _defaultApplicationName(context))),
       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` argument is 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
 }) {
   showDialog<Null>(
     context: context,
     child: new AboutDialog(
       applicationName: applicationName,
       applicationVersion: applicationVersion,
       applicationIcon: applicationIcon,
       applicationLegalese: applicationLegalese,
       children: children
     )
   );
 }

 /// Displays a [LicensePage], which shows licenses for software used by the
 /// application.
 ///
 /// The arguments correspond to the properties on [LicensePage].
 ///
 /// 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
 }) {
   // TODO(ianh): remove pop once https://github.com/flutter/flutter/issues/4667 is fixed
   Navigator.pop(context);
   Navigator.push(context, new MaterialPageRoute<Null>(
     builder: (BuildContext context) => new LicensePage(
       applicationName: applicationName,
       applicationVersion: applicationVersion,
       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) {
     final String name = applicationName ?? _defaultApplicationName(context);
     final String version = applicationVersion ?? _defaultApplicationVersion(context);
     final Widget icon = applicationIcon ?? _defaultApplicationIcon(context);
     List<Widget> body = <Widget>[];
     if (icon != null)
       body.add(new IconTheme(data: const IconThemeData(size: 48.0), child: icon));
     body.add(new Expanded(
       child: new Padding(
         padding: const EdgeInsets.symmetric(horizontal: 24.0),
         child: new ListBody(
           children: <Widget>[
             new Text(name, style: Theme.of(context).textTheme.headline),
             new Text(version, style: Theme.of(context).textTheme.body1),
             new Container(height: 18.0),
             new Text(applicationLegalese ?? '', style: Theme.of(context).textTheme.caption)
           ]
         )
       )
     ));
     body = <Widget>[
       new Row(
         crossAxisAlignment: CrossAxisAlignment.start,
         children: body
       ),
     ];
     if (children != null)
       body.addAll(children);
     return new AlertDialog(
       content: new SingleChildScrollView(
         child: new ListBody(children: body),
       ),
       actions: <Widget>[
         new FlatButton(
           child: new Text(MaterialLocalizations.of(context).viewLicensesButtonLabel),
           onPressed: () {
             showLicensePage(
               context: context,
               applicationName: applicationName,
               applicationVersion: applicationVersion,
               applicationIcon: applicationIcon,
               applicationLegalese: applicationLegalese
             );
           }
         ),
         new FlatButton(
           child: new Text(MaterialLocalizations.of(context).closeButtonLabel),
           onPressed: () {
             Navigator.pop(context);
           }
         ),
       ]
     );
   }
 }

 /// 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.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;

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

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

 class _LicensePageState extends State<LicensePage> {

   @override
   void initState() {
     super.initState();
     _initLicenses();
   }

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

   Future<Null> _initLicenses() async {
     await for (LicenseEntry license in LicenseRegistry.licenses) {
       if (!mounted)
         return;
       setState(() {
         _licenses.add(const Padding(
           padding: const EdgeInsets.symmetric(vertical: 18.0),
           child: const Text(
             '🍀‬', // That's U+1F340. Could also use U+2766 (❦) if U+1F340 doesn't work everywhere.
             textAlign: TextAlign.center
           )
         ));
         _licenses.add(new Container(
           decoration: const BoxDecoration(
             border: const Border(bottom: const BorderSide(width: 0.0))
           ),
           child: new Text(
             license.packages.join(', '),
             style: const TextStyle(fontWeight: FontWeight.bold),
             textAlign: TextAlign.center
           )
         ));
         for (LicenseParagraph paragraph in license.paragraphs) {
           if (paragraph.indent == LicenseParagraph.centeredIndent) {
             _licenses.add(new Padding(
               padding: const EdgeInsets.only(top: 16.0),
               child: new Text(
                 paragraph.text,
                 style: const TextStyle(fontWeight: FontWeight.bold),
                 textAlign: TextAlign.center
               )
             ));
           } else {
             assert(paragraph.indent >= 0);
             _licenses.add(new Padding(
               padding: new EdgeInsetsDirectional.only(top: 8.0, start: 16.0 * paragraph.indent),
               child: new Text(paragraph.text)
             ));
           }
         }
       });
     }
     setState(() {
       _loaded = true;
     });
   }

   @override
   Widget build(BuildContext context) {
     final String name = widget.applicationName ?? _defaultApplicationName(context);
     final String version = widget.applicationVersion ?? _defaultApplicationVersion(context);
     final MaterialLocalizations localizations = MaterialLocalizations.of(context);
     final List<Widget> contents = <Widget>[
       new Text(name, style: Theme.of(context).textTheme.headline, textAlign: TextAlign.center),
       new Text(version, style: Theme.of(context).textTheme.body1, textAlign: TextAlign.center),
       new Container(height: 18.0),
       new Text(widget.applicationLegalese ?? '', style: Theme.of(context).textTheme.caption, textAlign: TextAlign.center),
       new Container(height: 18.0),
       new Text('Powered by Flutter', style: Theme.of(context).textTheme.body1, textAlign: TextAlign.center),
       new Container(height: 24.0),
     ];
     contents.addAll(_licenses);
     if (!_loaded) {
       contents.add(const Padding(
         padding: const EdgeInsets.symmetric(vertical: 24.0),
         child: const Center(
           child: const CircularProgressIndicator()
         )
       ));
     }
     return new Scaffold(
       appBar: new AppBar(
         title: new Text(localizations.licensesPageTitle),
       ),
       // All of the licenses page text is English. We don't want localized text
       // or text direction.
       body: new Localizations.override(
         locale: const Locale('en', 'US'),
         context: context,
         child: new DefaultTextStyle(
           style: Theme.of(context).textTheme.caption,
           child: new Scrollbar(
             child: new ListView(
               padding: const EdgeInsets.symmetric(horizontal: 8.0, vertical: 12.0),
               shrinkWrap: true,
               children: contents,
             ),
           ),
         ),
       ),
     );
   }
 }

 String _defaultApplicationName(BuildContext context) {
   final Title ancestorTitle = context.ancestorWidgetOfExactType(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 2016 The Chromium 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:io' show Platform;

	import 'package:flutter/widgets.dart';
	import 'package:flutter/foundation.dart';

	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].
	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: const Icon(null),
	this.child,
	this.applicationName,
	this.applicationVersion,
	this.applicationIcon,
	this.applicationLegalese,
	this.aboutBoxChildren
	}) : 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;

	@override
	Widget build(BuildContext context) {
	assert(debugCheckHasMaterial(context));
	return new ListTile(
	leading: icon,
	title: child ??
	new Text(MaterialLocalizations.of(context).aboutListTileTitle(applicationName ?? _defaultApplicationName(context))),
	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` argument is 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
	}) {
	showDialog<Null>(
	context: context,
	child: new AboutDialog(
	applicationName: applicationName,
	applicationVersion: applicationVersion,
	applicationIcon: applicationIcon,
	applicationLegalese: applicationLegalese,
	children: children
	)
	);
	}

	/// Displays a [LicensePage], which shows licenses for software used by the
	/// application.
	///
	/// The arguments correspond to the properties on [LicensePage].
	///
	/// 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
	}) {
	// TODO(ianh): remove pop once https://github.com/flutter/flutter/issues/4667 is fixed
	Navigator.pop(context);
	Navigator.push(context, new MaterialPageRoute<Null>(
	builder: (BuildContext context) => new LicensePage(
	applicationName: applicationName,
	applicationVersion: applicationVersion,
	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) {
	final String name = applicationName ?? _defaultApplicationName(context);
	final String version = applicationVersion ?? _defaultApplicationVersion(context);
	final Widget icon = applicationIcon ?? _defaultApplicationIcon(context);
	List<Widget> body = <Widget>[];
	if (icon != null)
	body.add(new IconTheme(data: const IconThemeData(size: 48.0), child: icon));
	body.add(new Expanded(
	child: new Padding(
	padding: const EdgeInsets.symmetric(horizontal: 24.0),
	child: new ListBody(
	children: <Widget>[
	new Text(name, style: Theme.of(context).textTheme.headline),
	new Text(version, style: Theme.of(context).textTheme.body1),
	new Container(height: 18.0),
	new Text(applicationLegalese ?? '', style: Theme.of(context).textTheme.caption)
	]
	)
	)
	));
	body = <Widget>[
	new Row(
	crossAxisAlignment: CrossAxisAlignment.start,
	children: body
	),
	];
	if (children != null)
	body.addAll(children);
	return new AlertDialog(
	content: new SingleChildScrollView(
	child: new ListBody(children: body),
	),
	actions: <Widget>[
	new FlatButton(
	child: new Text(MaterialLocalizations.of(context).viewLicensesButtonLabel),
	onPressed: () {
	showLicensePage(
	context: context,
	applicationName: applicationName,
	applicationVersion: applicationVersion,
	applicationIcon: applicationIcon,
	applicationLegalese: applicationLegalese
	);
	}
	),
	new FlatButton(
	child: new Text(MaterialLocalizations.of(context).closeButtonLabel),
	onPressed: () {
	Navigator.pop(context);
	}
	),
	]
	);
	}
	}

	/// 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.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;

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

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

	class _LicensePageState extends State<LicensePage> {

	@override
	void initState() {
	super.initState();
	_initLicenses();
	}

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

	Future<Null> _initLicenses() async {
	await for (LicenseEntry license in LicenseRegistry.licenses) {
	if (!mounted)
	return;
	setState(() {
	_licenses.add(const Padding(
	padding: const EdgeInsets.symmetric(vertical: 18.0),
	child: const Text(
	'🍀‬', // That's U+1F340. Could also use U+2766 (❦) if U+1F340 doesn't work everywhere.
	textAlign: TextAlign.center
	)
	));
	_licenses.add(new Container(
	decoration: const BoxDecoration(
	border: const Border(bottom: const BorderSide(width: 0.0))
	),
	child: new Text(
	license.packages.join(', '),
	style: const TextStyle(fontWeight: FontWeight.bold),
	textAlign: TextAlign.center
	)
	));
	for (LicenseParagraph paragraph in license.paragraphs) {
	if (paragraph.indent == LicenseParagraph.centeredIndent) {
	_licenses.add(new Padding(
	padding: const EdgeInsets.only(top: 16.0),
	child: new Text(
	paragraph.text,
	style: const TextStyle(fontWeight: FontWeight.bold),
	textAlign: TextAlign.center
	)
	));
	} else {
	assert(paragraph.indent >= 0);
	_licenses.add(new Padding(
	padding: new EdgeInsetsDirectional.only(top: 8.0, start: 16.0 * paragraph.indent),
	child: new Text(paragraph.text)
	));
	}
	}
	});
	}
	setState(() {
	_loaded = true;
	});
	}

	@override
	Widget build(BuildContext context) {
	final String name = widget.applicationName ?? _defaultApplicationName(context);
	final String version = widget.applicationVersion ?? _defaultApplicationVersion(context);
	final MaterialLocalizations localizations = MaterialLocalizations.of(context);
	final List<Widget> contents = <Widget>[
	new Text(name, style: Theme.of(context).textTheme.headline, textAlign: TextAlign.center),
	new Text(version, style: Theme.of(context).textTheme.body1, textAlign: TextAlign.center),
	new Container(height: 18.0),
	new Text(widget.applicationLegalese ?? '', style: Theme.of(context).textTheme.caption, textAlign: TextAlign.center),
	new Container(height: 18.0),
	new Text('Powered by Flutter', style: Theme.of(context).textTheme.body1, textAlign: TextAlign.center),
	new Container(height: 24.0),
	];
	contents.addAll(_licenses);
	if (!_loaded) {
	contents.add(const Padding(
	padding: const EdgeInsets.symmetric(vertical: 24.0),
	child: const Center(
	child: const CircularProgressIndicator()
	)
	));
	}
	return new Scaffold(
	appBar: new AppBar(
	title: new Text(localizations.licensesPageTitle),
	),
	// All of the licenses page text is English. We don't want localized text
	// or text direction.
	body: new Localizations.override(
	locale: const Locale('en', 'US'),
	context: context,
	child: new DefaultTextStyle(
	style: Theme.of(context).textTheme.caption,
	child: new Scrollbar(
	child: new ListView(
	padding: const EdgeInsets.symmetric(horizontal: 8.0, vertical: 12.0),
	shrinkWrap: true,
	children: contents,
	),
	),
	),
	),
	);
	}
	}

	String _defaultApplicationName(BuildContext context) {
	final Title ancestorTitle = context.ancestorWidgetOfExactType(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;
	}