packages/flutter/lib/src/material/app.dart - external/github.com/flutter/flutter - Git at Google

 // Copyright 2015 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 'package:flutter/rendering.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/widgets.dart';

 import 'arc.dart';
 import 'colors.dart';
 import 'page.dart';
 import 'theme.dart';

 export 'dart:ui' show Locale;

 const TextStyle _errorTextStyle = const TextStyle(
   color: const Color(0xD0FF0000),
   fontFamily: 'monospace',
   fontSize: 48.0,
   fontWeight: FontWeight.w900,
   decoration: TextDecoration.underline,
   decorationColor: const Color(0xFFFFFF00),
   decorationStyle: TextDecorationStyle.double
 );

 /// An application that uses material design.
 ///
 /// A convenience widget that wraps a number of widgets that are commonly
 /// required for material design applications. It builds upon a [WidgetsApp] by
 /// adding material-design specific functionality, such as [AnimatedTheme] and
 /// [GridPaper].
 ///
 /// The [MaterialApp] configures the top-level [Navigator] to search for routes
 /// in the following order:
 ///
 ///  1. For the `/` route, the [home] property, if non-null, is used.
 ///
 ///  2. Otherwise, the [routes] table is used, if it has an entry for the route.
 ///
 ///  3. Otherwise, [onGenerateRoute] is called, if provided. It should return a
 ///     non-null value for any _valid_ route not handled by [home] and [routes].
 ///
 ///  4. Finally if all else fails [onUnknownRoute] is called.
 ///
 /// At least one of these options must handle the `/` route, since it is used
 /// when an invalid [initialRoute] is specified on startup (e.g. by another
 /// application launching this one with an intent on Android; see
 /// [Window.defaultRouteName]).
 ///
 /// This widget also configures the top-level [Navigator]'s observer to perform
 /// [Hero] animations.
 ///
 /// See also:
 ///
 ///  * [Scaffold], which provides standard app elements like an [AppBar] and a [Drawer].
 ///  * [Navigator], which is used to manage the app's stack of pages.
 ///  * [MaterialPageRoute], which defines an app page that transitions in a material-specific way.
 ///  * [WidgetsApp], which defines the basic app elements but does not depend on the material library.
 class MaterialApp extends StatefulWidget {
   /// Creates a MaterialApp.
   ///
   /// At least one of [home], [routes], or [onGenerateRoute] must be given. If
   /// only [routes] is given, it must include an entry for the
   /// [Navigator.defaultRouteName] (`/`), since that is the route used when the
   /// application is launched with an intent that specifies an otherwise
   /// unsupported route.
   ///
   /// This class creates an instance of [WidgetsApp].
   ///
   /// The boolean arguments, [routes], and [navigatorObservers], must not be null.
   MaterialApp({ // can't be const because the asserts use methods on Map :-(
     Key key,
     this.title,
     this.color,
     this.theme,
     this.home,
     this.routes: const <String, WidgetBuilder>{},
     this.initialRoute,
     this.onGenerateRoute,
     this.onUnknownRoute,
     this.onLocaleChanged,
     this.navigatorObservers: const <NavigatorObserver>[],
     this.debugShowMaterialGrid: false,
     this.showPerformanceOverlay: false,
     this.checkerboardRasterCacheImages: false,
     this.checkerboardOffscreenLayers: false,
     this.showSemanticsDebugger: false,
     this.debugShowCheckedModeBanner: true
   }) : assert(routes != null),
        assert(navigatorObservers != null),
        assert(debugShowMaterialGrid != null),
        assert(showPerformanceOverlay != null),
        assert(checkerboardRasterCacheImages != null),
        assert(checkerboardOffscreenLayers != null),
        assert(showSemanticsDebugger != null),
        assert(debugShowCheckedModeBanner != null),
        assert(
          home == null ||
          !routes.containsKey(Navigator.defaultRouteName),
          'If the home property is specified, the routes table '
          'cannot include an entry for "/", since it would be redundant.'
        ),
        assert(
          home != null ||
          routes.containsKey(Navigator.defaultRouteName) ||
          onGenerateRoute != null ||
          onUnknownRoute != null,
          'Either the home property must be specified, '
          'or the routes table must include an entry for "/", '
          'or there must be on onGenerateRoute callback specified, '
          'or there must be an onUnknownRoute callback specified, '
          'because otherwise there is nothing to fall back on if the '
          'app is started with an intent that specifies an unknown route.'
        ),
        super(key: key);

   /// A one-line description of this app for use in the window manager.
   final String title;

   /// The colors to use for the application's widgets.
   final ThemeData theme;

   /// The widget for the default route of the app ([Navigator.defaultRouteName],
   /// which is `/`).
   ///
   /// This is the route that is displayed first when the application is started
   /// normally, unless [initialRoute] is specified. It's also the route that's
   /// displayed if the [initialRoute] can't be displayed.
   ///
   /// To be able to directly call [Theme.of], [MediaQuery.of],
   /// [LocaleQuery.of], etc, in the code sets the [home] argument in
   /// the constructor, you can use a [Builder] widget to get a
   /// [BuildContext].
   ///
   /// If [home] is specified, then [routes] must not include an entry for `/`,
   /// as [home] takes its place.
   final Widget home;

   /// The primary color to use for the application in the operating system
   /// interface.
   ///
   /// For example, on Android this is the color used for the application in the
   /// application switcher.
   final Color color;

   /// The application's top-level routing table.
   ///
   /// When a named route is pushed with [Navigator.pushNamed], the route name is
   /// looked up in this map. If the name is present, the associated
   /// [WidgetBuilder] is used to construct a [MaterialPageRoute] that performs
   /// an appropriate transition, including [Hero] animations, to the new route.
   ///
   /// If the app only has one page, then you can specify it using [home] instead.
   ///
   /// If [home] is specified, then it implies an entry in this table for the
   /// [Navigator.defaultRouteName] route (`/`), and it is an error to
   /// redundantly provide such a route in the [routes] table.
   ///
   /// If a route is requested that is not specified in this table (or by
   /// [home]), then the [onGenerateRoute] callback is called to build the page
   /// instead.
   final Map<String, WidgetBuilder> routes;

   /// The name of the first route to show.
   ///
   /// Defaults to [Window.defaultRouteName], which may be overridden by the code
   /// that launched the application.
   ///
   /// If the route contains slashes, then it is treated as a "deep link", and
   /// before this route is pushed, the routes leading to this one are pushed
   /// also. For example, if the route was `/a/b/c`, then the app would start
   /// with the three routes `/a`, `/a/b`, and `/a/b/c` loaded, in that order.
   ///
   /// If any part of this process fails to generate routes, then the
   /// [initialRoute] is ignored and [Navigator.defaultRouteName] is used instead
   /// (`/`). This can happen if the app is started with an intent that specifies
   /// a non-existent route.
   ///
   /// See also:
   ///
   ///  * [Navigator.initialRoute], which is used to implement this property.
   ///  * [Navigator.push], for pushing additional routes.
   ///  * [Navigator.pop], for removing a route from the stack.
   final String initialRoute;

   /// The route generator callback used when the app is navigated to a
   /// named route.
   ///
   /// This is used if [routes] does not contain the requested route.
   ///
   /// If this returns null when building the routes to handle the specified
   /// [initialRoute], then all the routes are discarded and
   /// [Navigator.defaultRouteName] is used instead (`/`). See [initialRoute].
   ///
   /// During normal app operation, the [onGenerateRoute] callback will only be
   /// applied to route names pushed by the application, and so should never
   /// return null.
   final RouteFactory onGenerateRoute;

   /// Called when [onGenerateRoute] fails to generate a route, except for the
   /// [initialRoute].
   ///
   /// This callback is typically used for error handling. For example, this
   /// callback might always generate a "not found" page that describes the route
   /// that wasn't found.
   ///
   /// The default implementation pushes a route that displays an ugly error
   /// message.
   final RouteFactory onUnknownRoute;

   /// Callback that is called when the operating system changes the
   /// current locale.
   final LocaleChangedCallback onLocaleChanged;

   /// Turns on a performance overlay.
   ///
   /// See also:
   ///
   ///  * <https://flutter.io/debugging/#performanceoverlay>
   final bool showPerformanceOverlay;

   /// Turns on checkerboarding of raster cache images.
   final bool checkerboardRasterCacheImages;

   /// Turns on checkerboarding of layers rendered to offscreen bitmaps.
   final bool checkerboardOffscreenLayers;

   /// Turns on an overlay that shows the accessibility information
   /// reported by the framework.
   final bool showSemanticsDebugger;

   /// Turns on a little "SLOW MODE" banner in checked mode to indicate
   /// that the app is in checked mode. This is on by default (in
   /// checked mode), to turn it off, set the constructor argument to
   /// false. In release mode this has no effect.
   ///
   /// To get this banner in your application if you're not using
   /// WidgetsApp, include a [CheckedModeBanner] widget in your app.
   ///
   /// This banner is intended to deter people from complaining that your
   /// app is slow when it's in checked mode. In checked mode, Flutter
   /// enables a large number of expensive diagnostics to aid in
   /// development, and so performance in checked mode is not
   /// representative of what will happen in release mode.
   final bool debugShowCheckedModeBanner;

   /// The list of observers for the [Navigator] created for this app.
   final List<NavigatorObserver> navigatorObservers;

   /// Turns on a [GridPaper] overlay that paints a baseline grid
   /// Material apps.
   ///
   /// Only available in checked mode.
   ///
   /// See also:
   ///
   ///  * <https://material.google.com/layout/metrics-keylines.html>
   final bool debugShowMaterialGrid;

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

 class _MaterialScrollBehavior extends ScrollBehavior {
   @override
   TargetPlatform getPlatform(BuildContext context) {
     return Theme.of(context).platform;
   }

   @override
   Widget buildViewportChrome(BuildContext context, Widget child, AxisDirection axisDirection) {
     // When modifying this function, consider modifying the implementation in
     // the base class as well.
     switch (getPlatform(context)) {
       case TargetPlatform.iOS:
         return child;
       case TargetPlatform.android:
       case TargetPlatform.fuchsia:
         return new GlowingOverscrollIndicator(
           child: child,
           axisDirection: axisDirection,
           color: Theme.of(context).accentColor,
         );
     }
     return null;
   }
 }

 class _MaterialAppState extends State<MaterialApp> {
   HeroController _heroController;

   @override
   void initState() {
     super.initState();
     _heroController = new HeroController(createRectTween: _createRectTween);
   }

   RectTween _createRectTween(Rect begin, Rect end) {
     return new MaterialRectArcTween(begin: begin, end: end);
   }

   Route<dynamic> _onGenerateRoute(RouteSettings settings) {
     final String name = settings.name;
     WidgetBuilder builder;
     if (name == Navigator.defaultRouteName && widget.home != null)
       builder = (BuildContext context) => widget.home;
     else
       builder = widget.routes[name];
     if (builder != null) {
       return new MaterialPageRoute<dynamic>(
         builder: builder,
         settings: settings,
       );
     }
     if (widget.onGenerateRoute != null)
       return widget.onGenerateRoute(settings);
     return null;
   }

   Route<dynamic> _onUnknownRoute(RouteSettings settings) {
     assert(() {
       if (widget.onUnknownRoute == null) {
         throw new FlutterError(
           'Could not find a generator for route $settings in the $runtimeType.\n'
           'Generators for routes are searched for in the following order:\n'
           ' 1. For the "/" route, the "home" property, if non-null, is used.\n'
           ' 2. Otherwise, the "routes" table is used, if it has an entry for '
           'the route.\n'
           ' 3. Otherwise, onGenerateRoute is called. It should return a '
           'non-null value for any valid route not handled by "home" and "routes".\n'
           ' 4. Finally if all else fails onUnknownRoute is called.\n'
           'Unfortunately, onUnknownRoute was not set.'
         );
       }
       return true;
     });
     final Route<dynamic> result = widget.onUnknownRoute(settings);
     assert(() {
       if (result == null) {
         throw new FlutterError(
           'The onUnknownRoute callback returned null.\n'
           'When the $runtimeType requested the route $settings from its '
           'onUnknownRoute callback, the callback returned null. Such callbacks '
           'must never return null.'
         );
       }
       return true;
     });
     return result;
   }

   @override
   Widget build(BuildContext context) {
     final ThemeData theme = widget.theme ?? new ThemeData.fallback();
     Widget result = new AnimatedTheme(
       data: theme,
       isMaterialAppTheme: true,
       child: new WidgetsApp(
         key: new GlobalObjectKey(this),
         title: widget.title,
         textStyle: _errorTextStyle,
         // blue is the primary color of the default theme
         color: widget.color ?? theme?.primaryColor ?? Colors.blue,
         navigatorObservers:
             new List<NavigatorObserver>.from(widget.navigatorObservers)
               ..add(_heroController),
         initialRoute: widget.initialRoute,
         onGenerateRoute: _onGenerateRoute,
         onUnknownRoute: _onUnknownRoute,
         onLocaleChanged: widget.onLocaleChanged,
         showPerformanceOverlay: widget.showPerformanceOverlay,
         checkerboardRasterCacheImages: widget.checkerboardRasterCacheImages,
         checkerboardOffscreenLayers: widget.checkerboardOffscreenLayers,
         showSemanticsDebugger: widget.showSemanticsDebugger,
         debugShowCheckedModeBanner: widget.debugShowCheckedModeBanner,
       )
     );

     assert(() {
       if (widget.debugShowMaterialGrid) {
         result = new GridPaper(
           color: const Color(0xE0F9BBE0),
           interval: 8.0,
           divisions: 2,
           subdivisions: 1,
           child: result,
         );
       }
       return true;
     });

     return new ScrollConfiguration(
       behavior: new _MaterialScrollBehavior(),
       child: result,
     );
   }
 }
	// Copyright 2015 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 'package:flutter/rendering.dart';
	import 'package:flutter/foundation.dart';
	import 'package:flutter/widgets.dart';

	import 'arc.dart';
	import 'colors.dart';
	import 'page.dart';
	import 'theme.dart';

	export 'dart:ui' show Locale;

	const TextStyle _errorTextStyle = const TextStyle(
	color: const Color(0xD0FF0000),
	fontFamily: 'monospace',
	fontSize: 48.0,
	fontWeight: FontWeight.w900,
	decoration: TextDecoration.underline,
	decorationColor: const Color(0xFFFFFF00),
	decorationStyle: TextDecorationStyle.double
	);

	/// An application that uses material design.
	///
	/// A convenience widget that wraps a number of widgets that are commonly
	/// required for material design applications. It builds upon a [WidgetsApp] by
	/// adding material-design specific functionality, such as [AnimatedTheme] and
	/// [GridPaper].
	///
	/// The [MaterialApp] configures the top-level [Navigator] to search for routes
	/// in the following order:
	///
	/// 1. For the `/` route, the [home] property, if non-null, is used.
	///
	/// 2. Otherwise, the [routes] table is used, if it has an entry for the route.
	///
	/// 3. Otherwise, [onGenerateRoute] is called, if provided. It should return a
	/// non-null value for any _valid_ route not handled by [home] and [routes].
	///
	/// 4. Finally if all else fails [onUnknownRoute] is called.
	///
	/// At least one of these options must handle the `/` route, since it is used
	/// when an invalid [initialRoute] is specified on startup (e.g. by another
	/// application launching this one with an intent on Android; see
	/// [Window.defaultRouteName]).
	///
	/// This widget also configures the top-level [Navigator]'s observer to perform
	/// [Hero] animations.
	///
	/// See also:
	///
	/// * [Scaffold], which provides standard app elements like an [AppBar] and a [Drawer].
	/// * [Navigator], which is used to manage the app's stack of pages.
	/// * [MaterialPageRoute], which defines an app page that transitions in a material-specific way.
	/// * [WidgetsApp], which defines the basic app elements but does not depend on the material library.
	class MaterialApp extends StatefulWidget {
	/// Creates a MaterialApp.
	///
	/// At least one of [home], [routes], or [onGenerateRoute] must be given. If
	/// only [routes] is given, it must include an entry for the
	/// [Navigator.defaultRouteName] (`/`), since that is the route used when the
	/// application is launched with an intent that specifies an otherwise
	/// unsupported route.
	///
	/// This class creates an instance of [WidgetsApp].
	///
	/// The boolean arguments, [routes], and [navigatorObservers], must not be null.
	MaterialApp({ // can't be const because the asserts use methods on Map :-(
	Key key,
	this.title,
	this.color,
	this.theme,
	this.home,
	this.routes: const <String, WidgetBuilder>{},
	this.initialRoute,
	this.onGenerateRoute,
	this.onUnknownRoute,
	this.onLocaleChanged,
	this.navigatorObservers: const <NavigatorObserver>[],
	this.debugShowMaterialGrid: false,
	this.showPerformanceOverlay: false,
	this.checkerboardRasterCacheImages: false,
	this.checkerboardOffscreenLayers: false,
	this.showSemanticsDebugger: false,
	this.debugShowCheckedModeBanner: true
	}) : assert(routes != null),
	assert(navigatorObservers != null),
	assert(debugShowMaterialGrid != null),
	assert(showPerformanceOverlay != null),
	assert(checkerboardRasterCacheImages != null),
	assert(checkerboardOffscreenLayers != null),
	assert(showSemanticsDebugger != null),
	assert(debugShowCheckedModeBanner != null),
	assert(
	home == null \|\|
	!routes.containsKey(Navigator.defaultRouteName),
	'If the home property is specified, the routes table '
	'cannot include an entry for "/", since it would be redundant.'
	),
	assert(
	home != null \|\|
	routes.containsKey(Navigator.defaultRouteName) \|\|
	onGenerateRoute != null \|\|
	onUnknownRoute != null,
	'Either the home property must be specified, '
	'or the routes table must include an entry for "/", '
	'or there must be on onGenerateRoute callback specified, '
	'or there must be an onUnknownRoute callback specified, '
	'because otherwise there is nothing to fall back on if the '
	'app is started with an intent that specifies an unknown route.'
	),
	super(key: key);

	/// A one-line description of this app for use in the window manager.
	final String title;

	/// The colors to use for the application's widgets.
	final ThemeData theme;

	/// The widget for the default route of the app ([Navigator.defaultRouteName],
	/// which is `/`).
	///
	/// This is the route that is displayed first when the application is started
	/// normally, unless [initialRoute] is specified. It's also the route that's
	/// displayed if the [initialRoute] can't be displayed.
	///
	/// To be able to directly call [Theme.of], [MediaQuery.of],
	/// [LocaleQuery.of], etc, in the code sets the [home] argument in
	/// the constructor, you can use a [Builder] widget to get a
	/// [BuildContext].
	///
	/// If [home] is specified, then [routes] must not include an entry for `/`,
	/// as [home] takes its place.
	final Widget home;

	/// The primary color to use for the application in the operating system
	/// interface.
	///
	/// For example, on Android this is the color used for the application in the
	/// application switcher.
	final Color color;

	/// The application's top-level routing table.
	///
	/// When a named route is pushed with [Navigator.pushNamed], the route name is
	/// looked up in this map. If the name is present, the associated
	/// [WidgetBuilder] is used to construct a [MaterialPageRoute] that performs
	/// an appropriate transition, including [Hero] animations, to the new route.
	///
	/// If the app only has one page, then you can specify it using [home] instead.
	///
	/// If [home] is specified, then it implies an entry in this table for the
	/// [Navigator.defaultRouteName] route (`/`), and it is an error to
	/// redundantly provide such a route in the [routes] table.
	///
	/// If a route is requested that is not specified in this table (or by
	/// [home]), then the [onGenerateRoute] callback is called to build the page
	/// instead.
	final Map<String, WidgetBuilder> routes;

	/// The name of the first route to show.
	///
	/// Defaults to [Window.defaultRouteName], which may be overridden by the code
	/// that launched the application.
	///
	/// If the route contains slashes, then it is treated as a "deep link", and
	/// before this route is pushed, the routes leading to this one are pushed
	/// also. For example, if the route was `/a/b/c`, then the app would start
	/// with the three routes `/a`, `/a/b`, and `/a/b/c` loaded, in that order.
	///
	/// If any part of this process fails to generate routes, then the
	/// [initialRoute] is ignored and [Navigator.defaultRouteName] is used instead
	/// (`/`). This can happen if the app is started with an intent that specifies
	/// a non-existent route.
	///
	/// See also:
	///
	/// * [Navigator.initialRoute], which is used to implement this property.
	/// * [Navigator.push], for pushing additional routes.
	/// * [Navigator.pop], for removing a route from the stack.
	final String initialRoute;

	/// The route generator callback used when the app is navigated to a
	/// named route.
	///
	/// This is used if [routes] does not contain the requested route.
	///
	/// If this returns null when building the routes to handle the specified
	/// [initialRoute], then all the routes are discarded and
	/// [Navigator.defaultRouteName] is used instead (`/`). See [initialRoute].
	///
	/// During normal app operation, the [onGenerateRoute] callback will only be
	/// applied to route names pushed by the application, and so should never
	/// return null.
	final RouteFactory onGenerateRoute;

	/// Called when [onGenerateRoute] fails to generate a route, except for the
	/// [initialRoute].
	///
	/// This callback is typically used for error handling. For example, this
	/// callback might always generate a "not found" page that describes the route
	/// that wasn't found.
	///
	/// The default implementation pushes a route that displays an ugly error
	/// message.
	final RouteFactory onUnknownRoute;

	/// Callback that is called when the operating system changes the
	/// current locale.
	final LocaleChangedCallback onLocaleChanged;

	/// Turns on a performance overlay.
	///
	/// See also:
	///
	/// * <https://flutter.io/debugging/#performanceoverlay>
	final bool showPerformanceOverlay;

	/// Turns on checkerboarding of raster cache images.
	final bool checkerboardRasterCacheImages;

	/// Turns on checkerboarding of layers rendered to offscreen bitmaps.
	final bool checkerboardOffscreenLayers;

	/// Turns on an overlay that shows the accessibility information
	/// reported by the framework.
	final bool showSemanticsDebugger;

	/// Turns on a little "SLOW MODE" banner in checked mode to indicate
	/// that the app is in checked mode. This is on by default (in
	/// checked mode), to turn it off, set the constructor argument to
	/// false. In release mode this has no effect.
	///
	/// To get this banner in your application if you're not using
	/// WidgetsApp, include a [CheckedModeBanner] widget in your app.
	///
	/// This banner is intended to deter people from complaining that your
	/// app is slow when it's in checked mode. In checked mode, Flutter
	/// enables a large number of expensive diagnostics to aid in
	/// development, and so performance in checked mode is not
	/// representative of what will happen in release mode.
	final bool debugShowCheckedModeBanner;

	/// The list of observers for the [Navigator] created for this app.
	final List<NavigatorObserver> navigatorObservers;

	/// Turns on a [GridPaper] overlay that paints a baseline grid
	/// Material apps.
	///
	/// Only available in checked mode.
	///
	/// See also:
	///
	/// * <https://material.google.com/layout/metrics-keylines.html>
	final bool debugShowMaterialGrid;

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

	class _MaterialScrollBehavior extends ScrollBehavior {
	@override
	TargetPlatform getPlatform(BuildContext context) {
	return Theme.of(context).platform;
	}

	@override
	Widget buildViewportChrome(BuildContext context, Widget child, AxisDirection axisDirection) {
	// When modifying this function, consider modifying the implementation in
	// the base class as well.
	switch (getPlatform(context)) {
	case TargetPlatform.iOS:
	return child;
	case TargetPlatform.android:
	case TargetPlatform.fuchsia:
	return new GlowingOverscrollIndicator(
	child: child,
	axisDirection: axisDirection,
	color: Theme.of(context).accentColor,
	);
	}
	return null;
	}
	}

	class _MaterialAppState extends State<MaterialApp> {
	HeroController _heroController;

	@override
	void initState() {
	super.initState();
	_heroController = new HeroController(createRectTween: _createRectTween);
	}

	RectTween _createRectTween(Rect begin, Rect end) {
	return new MaterialRectArcTween(begin: begin, end: end);
	}

	Route<dynamic> _onGenerateRoute(RouteSettings settings) {
	final String name = settings.name;
	WidgetBuilder builder;
	if (name == Navigator.defaultRouteName && widget.home != null)
	builder = (BuildContext context) => widget.home;
	else
	builder = widget.routes[name];
	if (builder != null) {
	return new MaterialPageRoute<dynamic>(
	builder: builder,
	settings: settings,
	);
	}
	if (widget.onGenerateRoute != null)
	return widget.onGenerateRoute(settings);
	return null;
	}

	Route<dynamic> _onUnknownRoute(RouteSettings settings) {
	assert(() {
	if (widget.onUnknownRoute == null) {
	throw new FlutterError(
	'Could not find a generator for route $settings in the $runtimeType.\n'
	'Generators for routes are searched for in the following order:\n'
	' 1. For the "/" route, the "home" property, if non-null, is used.\n'
	' 2. Otherwise, the "routes" table is used, if it has an entry for '
	'the route.\n'
	' 3. Otherwise, onGenerateRoute is called. It should return a '
	'non-null value for any valid route not handled by "home" and "routes".\n'
	' 4. Finally if all else fails onUnknownRoute is called.\n'
	'Unfortunately, onUnknownRoute was not set.'
	);
	}
	return true;
	});
	final Route<dynamic> result = widget.onUnknownRoute(settings);
	assert(() {
	if (result == null) {
	throw new FlutterError(
	'The onUnknownRoute callback returned null.\n'
	'When the $runtimeType requested the route $settings from its '
	'onUnknownRoute callback, the callback returned null. Such callbacks '
	'must never return null.'
	);
	}
	return true;
	});
	return result;
	}

	@override
	Widget build(BuildContext context) {
	final ThemeData theme = widget.theme ?? new ThemeData.fallback();
	Widget result = new AnimatedTheme(
	data: theme,
	isMaterialAppTheme: true,
	child: new WidgetsApp(
	key: new GlobalObjectKey(this),
	title: widget.title,
	textStyle: _errorTextStyle,
	// blue is the primary color of the default theme
	color: widget.color ?? theme?.primaryColor ?? Colors.blue,
	navigatorObservers:
	new List<NavigatorObserver>.from(widget.navigatorObservers)
	..add(_heroController),
	initialRoute: widget.initialRoute,
	onGenerateRoute: _onGenerateRoute,
	onUnknownRoute: _onUnknownRoute,
	onLocaleChanged: widget.onLocaleChanged,
	showPerformanceOverlay: widget.showPerformanceOverlay,
	checkerboardRasterCacheImages: widget.checkerboardRasterCacheImages,
	checkerboardOffscreenLayers: widget.checkerboardOffscreenLayers,
	showSemanticsDebugger: widget.showSemanticsDebugger,
	debugShowCheckedModeBanner: widget.debugShowCheckedModeBanner,
	)
	);

	assert(() {
	if (widget.debugShowMaterialGrid) {
	result = new GridPaper(
	color: const Color(0xE0F9BBE0),
	interval: 8.0,
	divisions: 2,
	subdivisions: 1,
	child: result,
	);
	}
	return true;
	});

	return new ScrollConfiguration(
	behavior: new _MaterialScrollBehavior(),
	child: result,
	);
	}
	}