packages/flutter/lib/src/services/system_chrome.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:ui';

 import 'package:flutter/foundation.dart';

 import 'system_channels.dart';

 export 'dart:ui' show Brightness;

 /// Specifies a particular device orientation.
 ///
 /// To determine which values correspond to which orientations, first position
 /// the device in its default orientation (this is the orientation that the
 /// system first uses for its boot logo, or the orientation in which the
 /// hardware logos or markings are upright, or the orientation in which the
 /// cameras are at the top). If this is a portrait orientation, then this is
 /// [portraitUp]. Otherwise, it's [landscapeLeft]. As you rotate the device by
 /// 90 degrees in a counter-clockwise direction around the axis that pierces the
 /// screen, you step through each value in this enum in the order given.
 ///
 /// For a device with a landscape default orientation, the orientation obtained
 /// by rotating the device 90 degrees clockwise from its default orientation is
 /// [portraitUp].
 ///
 /// Used by [SystemChrome.setPreferredOrientations].
 enum DeviceOrientation {
   /// If the device shows its boot logo in portrait, then the boot logo is shown
   /// in [portraitUp]. Otherwise, the device shows its boot logo in landscape
   /// and this orientation is obtained by rotating the device 90 degrees
   /// clockwise from its boot orientation.
   portraitUp,

   /// The orientation that is 90 degrees clockwise from [portraitUp].
   ///
   /// If the device shows its boot logo in landscape, then the boot logo is
   /// shown in [landscapeLeft].
   landscapeLeft,

   /// The orientation that is 180 degrees from [portraitUp].
   portraitDown,

   /// The orientation that is 90 degrees counterclockwise from [portraitUp].
   landscapeRight,
 }

 /// Specifies a description of the application that is pertinent to the
 /// embedder's application switcher (also known as "recent tasks") user
 /// interface.
 ///
 /// Used by [SystemChrome.setApplicationSwitcherDescription].
 @immutable
 class ApplicationSwitcherDescription {
   /// Creates an ApplicationSwitcherDescription.
   const ApplicationSwitcherDescription({ this.label, this.primaryColor });

   /// A label and description of the current state of the application.
   final String label;

   /// The application's primary color.
   ///
   /// This may influence the color that the operating system uses to represent
   /// the application.
   final int primaryColor;
 }

 /// Specifies a system overlay at a particular location.
 ///
 /// Used by [SystemChrome.setEnabledSystemUIOverlays].
 enum SystemUiOverlay {
   /// The status bar provided by the embedder on the top of the application
   /// surface, if any.
   top,

   /// The status bar provided by the embedder on the bottom of the application
   /// surface, if any.
   bottom,
 }

 /// Specifies a preference for the style of the system overlays.
 ///
 /// Used by [SystemChrome.setSystemUIOverlayStyle].
 @immutable
 class SystemUiOverlayStyle {
   /// Creates a new [SystemUiOverlayStyle].
   const SystemUiOverlayStyle({
     this.systemNavigationBarColor,
     this.systemNavigationBarDividerColor,
     this.systemNavigationBarIconBrightness,
     this.statusBarColor,
     this.statusBarBrightness,
     this.statusBarIconBrightness,
   });

   /// The color of the system bottom navigation bar.
   ///
   /// Only honored in Android versions O and greater.
   final Color systemNavigationBarColor;

   /// The color of the divider between the system's bottom navigation bar and the app's content.
   ///
   /// Only honored in Android versions P and greater.
   final Color systemNavigationBarDividerColor;

   /// The brightness of the system navigation bar icons.
   ///
   /// Only honored in Android versions O and greater.
   final Brightness systemNavigationBarIconBrightness;

   /// The color of top status bar.
   ///
   /// Only honored in Android version M and greater.
   final Color statusBarColor;

   /// The brightness of top status bar.
   ///
   /// Only honored in iOS.
   final Brightness statusBarBrightness;

   /// The brightness of the top status bar icons.
   ///
   /// Only honored in Android version M and greater.
   final Brightness statusBarIconBrightness;

   /// System overlays should be drawn with a light color. Intended for
   /// applications with a dark background.
   static const SystemUiOverlayStyle light = SystemUiOverlayStyle(
     systemNavigationBarColor: Color(0xFF000000),
     systemNavigationBarDividerColor: null,
     statusBarColor: null,
     systemNavigationBarIconBrightness: Brightness.light,
     statusBarIconBrightness: Brightness.light,
     statusBarBrightness: Brightness.dark,
   );

   /// System overlays should be drawn with a dark color. Intended for
   /// applications with a light background.
   static const SystemUiOverlayStyle dark = SystemUiOverlayStyle(
     systemNavigationBarColor: Color(0xFF000000),
     systemNavigationBarDividerColor: null,
     statusBarColor: null,
     systemNavigationBarIconBrightness: Brightness.light,
     statusBarIconBrightness: Brightness.dark,
     statusBarBrightness: Brightness.light,
   );

   /// Convert this event to a map for serialization.
   Map<String, dynamic> _toMap() {
     return <String, dynamic>{
       'systemNavigationBarColor': systemNavigationBarColor?.value,
       'systemNavigationBarDividerColor': systemNavigationBarDividerColor?.value,
       'statusBarColor': statusBarColor?.value,
       'statusBarBrightness': statusBarBrightness?.toString(),
       'statusBarIconBrightness': statusBarIconBrightness?.toString(),
       'systemNavigationBarIconBrightness': systemNavigationBarIconBrightness?.toString(),
     };
   }

   @override
   String toString() => _toMap().toString();

   /// Creates a copy of this theme with the given fields replaced with new values.
   SystemUiOverlayStyle copyWith({
     Color systemNavigationBarColor,
     Color systemNavigationBarDividerColor,
     Color statusBarColor,
     Brightness statusBarBrightness,
     Brightness statusBarIconBrightness,
     Brightness systemNavigationBarIconBrightness,
   }) {
     return SystemUiOverlayStyle(
       systemNavigationBarColor: systemNavigationBarColor ?? this.systemNavigationBarColor,
       systemNavigationBarDividerColor: systemNavigationBarDividerColor ?? this.systemNavigationBarDividerColor,
       statusBarColor: statusBarColor ?? this.statusBarColor,
       statusBarIconBrightness: statusBarIconBrightness ?? this.statusBarIconBrightness,
       statusBarBrightness: statusBarBrightness ?? this.statusBarBrightness,
       systemNavigationBarIconBrightness: systemNavigationBarIconBrightness ?? this.systemNavigationBarIconBrightness,
     );
   }

   @override
   int get hashCode {
     return hashValues(
       systemNavigationBarColor,
       systemNavigationBarDividerColor,
       statusBarColor,
       statusBarBrightness,
       statusBarIconBrightness,
       systemNavigationBarIconBrightness,
     );
   }

   @override
   bool operator ==(Object other) {
     if (other.runtimeType != runtimeType)
       return false;
     return other is SystemUiOverlayStyle
         && other.systemNavigationBarColor == systemNavigationBarColor
         && other.systemNavigationBarDividerColor == systemNavigationBarDividerColor
         && other.statusBarColor == statusBarColor
         && other.statusBarIconBrightness == statusBarIconBrightness
         && other.statusBarBrightness == statusBarBrightness
         && other.systemNavigationBarIconBrightness == systemNavigationBarIconBrightness;
   }
 }

 List<String> _stringify(List<dynamic> list) => <String>[
   for (final dynamic item in list) item.toString(),
 ];

 /// Controls specific aspects of the operating system's graphical interface and
 /// how it interacts with the application.
 class SystemChrome {
   // This class is not meant to be instatiated or extended; this constructor
   // prevents instantiation and extension.
   // ignore: unused_element
   SystemChrome._();

   /// Specifies the set of orientations the application interface can
   /// be displayed in.
   ///
   /// The `orientation` argument is a list of [DeviceOrientation] enum values.
   /// The empty list causes the application to defer to the operating system
   /// default.
   ///
   /// ## Limitations
   ///
   /// This setting will only be respected on iPad if multitasking is disabled.
   ///
   /// You can decide to opt out of multitasking on iPad, then
   /// setPreferredOrientations will work but your app will not
   /// support Slide Over and Split View multitasking anymore.
   ///
   /// Should you decide to opt out of multitasking you can do this by
   /// setting "Requires full screen" to true in the Xcode Deployment Info.
   static Future<void> setPreferredOrientations(List<DeviceOrientation> orientations) async {
     await SystemChannels.platform.invokeMethod<void>(
       'SystemChrome.setPreferredOrientations',
       _stringify(orientations),
     );
   }

   /// Specifies the description of the current state of the application as it
   /// pertains to the application switcher (also known as "recent tasks").
   ///
   /// Any part of the description that is unsupported on the current platform
   /// will be ignored.
   static Future<void> setApplicationSwitcherDescription(ApplicationSwitcherDescription description) async {
     await SystemChannels.platform.invokeMethod<void>(
       'SystemChrome.setApplicationSwitcherDescription',
       <String, dynamic>{
         'label': description.label,
         'primaryColor': description.primaryColor,
       },
     );
   }

   /// Specifies the set of system overlays to have visible when the application
   /// is running.
   ///
   /// The `overlays` argument is a list of [SystemUiOverlay] enum values
   /// denoting the overlays to show.
   ///
   /// If a particular overlay is unsupported on the platform, enabling or
   /// disabling that overlay will be ignored.
   ///
   /// The settings here can be overridden by the platform when System UI becomes
   /// necessary for functionality.
   ///
   /// For example, on Android, when the keyboard becomes visible, it will enable the
   /// navigation bar and status bar system UI overlays. When the keyboard is closed,
   /// Android will not restore the previous UI visibility settings, and the UI
   /// visibility cannot be changed until 1 second after the keyboard is closed to
   /// prevent malware locking users from navigation buttons.
   ///
   /// To regain "fullscreen" after text entry, the UI overlays should be set again
   /// after a delay of 1 second. This can be achieved through [restoreSystemUIOverlays]
   /// or calling this again. Otherwise, the original UI overlay settings will be
   /// automatically restored only when the application loses and regains focus.
   static Future<void> setEnabledSystemUIOverlays(List<SystemUiOverlay> overlays) async {
     await SystemChannels.platform.invokeMethod<void>(
       'SystemChrome.setEnabledSystemUIOverlays',
       _stringify(overlays),
     );
   }

   /// Restores the system overlays to the last settings provided via
   /// [setEnabledSystemUIOverlays]. May be used when the platform force enables/disables
   /// UI elements.
   ///
   /// For example, when the Android keyboard disables hidden status and navigation bars,
   /// this can be called to re-disable the bars when the keyboard is closed.
   ///
   /// On Android, the system UI cannot be changed until 1 second after the previous
   /// change. This is to prevent malware from permanently hiding navigation buttons.
   static Future<void> restoreSystemUIOverlays() async {
     await SystemChannels.platform.invokeMethod<void>(
       'SystemChrome.restoreSystemUIOverlays',
       null,
     );
   }

   /// Specifies the style to use for the system overlays that are visible (if
   /// any).
   ///
   /// This method will schedule the embedder update to be run in a microtask.
   /// Any subsequent calls to this method during the current event loop will
   /// overwrite the pending value, such that only the last specified value takes
   /// effect.
   ///
   /// Call this API in code whose lifecycle matches that of the desired
   /// system UI styles. For instance, to change the system UI style on a new
   /// page, consider calling when pushing/popping a new [PageRoute].
   ///
   /// However, the [AppBar] widget automatically sets the system overlay style
   /// based on its [AppBar.brightness], so configure that instead of calling
   /// this method directly. Likewise, do the same for [CupertinoNavigationBar]
   /// via [CupertinoNavigationBar.backgroundColor].
   ///
   /// If a particular style is not supported on the platform, selecting it will
   /// have no effect.
   ///
   /// {@tool snippet}
   /// ```dart
   /// @override
   /// Widget build(BuildContext context) {
   ///   SystemChrome.setSystemUIOverlayStyle(SystemUiOverlayStyle.dark);
   ///   return Placeholder();
   /// }
   /// ```
   /// {@end-tool}
   ///
   /// For more complex control of the system overlay styles, consider using
   /// an [AnnotatedRegion] widget instead of calling [setSystemUiOverlayStyle]
   /// directly. This widget places a value directly into the layer tree where
   /// it can be hit-tested by the framework. On every frame, the framework will
   /// hit-test and select the annotated region it finds under the status and
   /// navigation bar and synthesize them into a single style. This can be used
   /// to configure the system styles when an app bar is not used.
   ///
   /// {@tool sample --template=stateful_widget_material}
   /// The following example creates a widget that changes the status bar color
   /// to a random value on Android.
   ///
   /// ```dart imports
   /// import 'package:flutter/services.dart';
   /// import 'dart:math' as math;
   /// ```
   ///
   /// ```dart
   /// final _random = math.Random();
   /// SystemUiOverlayStyle _currentStyle = SystemUiOverlayStyle.light;
   ///
   /// void _changeColor() {
   ///   final color = Color.fromRGBO(
   ///     _random.nextInt(255),
   ///     _random.nextInt(255),
   ///     _random.nextInt(255),
   ///     1.0,
   ///   );
   ///   setState(() {
   ///     _currentStyle = SystemUiOverlayStyle.dark.copyWith(
   ///       statusBarColor: color,
   ///     );
   ///   });
   /// }
   ///
   /// @override
   /// Widget build(BuildContext context) {
   ///   return AnnotatedRegion(
   ///     value: _currentStyle,
   ///     child: Center(
   ///       child: RaisedButton(
   ///         child: const Text('Change Color'),
   ///         onPressed: _changeColor,
   ///        ),
   ///      ),
   ///    );
   ///  }
   /// ```
   /// {@end-tool}
   ///
   /// See also:
   ///
   ///  * [AnnotatedRegion], the widget used to place data into the layer tree.
   static void setSystemUIOverlayStyle(SystemUiOverlayStyle style) {
     assert(style != null);
     if (_pendingStyle != null) {
       // The microtask has already been queued; just update the pending value.
       _pendingStyle = style;
       return;
     }
     if (style == _latestStyle) {
       // Trivial success: no microtask has been queued and the given style is
       // already in effect, so no need to queue a microtask.
       return;
     }
     _pendingStyle = style;
     scheduleMicrotask(() {
       assert(_pendingStyle != null);
       if (_pendingStyle != _latestStyle) {
         SystemChannels.platform.invokeMethod<void>(
           'SystemChrome.setSystemUIOverlayStyle',
           _pendingStyle._toMap(),
         );
         _latestStyle = _pendingStyle;
       }
       _pendingStyle = null;
     });
   }

   static SystemUiOverlayStyle _pendingStyle;

   /// The last style that was set using [SystemChrome.setSystemUIOverlayStyle].
   @visibleForTesting
   static SystemUiOverlayStyle get latestStyle => _latestStyle;
   static SystemUiOverlayStyle _latestStyle;
 }
	// 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:ui';

	import 'package:flutter/foundation.dart';

	import 'system_channels.dart';

	export 'dart:ui' show Brightness;

	/// Specifies a particular device orientation.
	///
	/// To determine which values correspond to which orientations, first position
	/// the device in its default orientation (this is the orientation that the
	/// system first uses for its boot logo, or the orientation in which the
	/// hardware logos or markings are upright, or the orientation in which the
	/// cameras are at the top). If this is a portrait orientation, then this is
	/// [portraitUp]. Otherwise, it's [landscapeLeft]. As you rotate the device by
	/// 90 degrees in a counter-clockwise direction around the axis that pierces the
	/// screen, you step through each value in this enum in the order given.
	///
	/// For a device with a landscape default orientation, the orientation obtained
	/// by rotating the device 90 degrees clockwise from its default orientation is
	/// [portraitUp].
	///
	/// Used by [SystemChrome.setPreferredOrientations].
	enum DeviceOrientation {
	/// If the device shows its boot logo in portrait, then the boot logo is shown
	/// in [portraitUp]. Otherwise, the device shows its boot logo in landscape
	/// and this orientation is obtained by rotating the device 90 degrees
	/// clockwise from its boot orientation.
	portraitUp,

	/// The orientation that is 90 degrees clockwise from [portraitUp].
	///
	/// If the device shows its boot logo in landscape, then the boot logo is
	/// shown in [landscapeLeft].
	landscapeLeft,

	/// The orientation that is 180 degrees from [portraitUp].
	portraitDown,

	/// The orientation that is 90 degrees counterclockwise from [portraitUp].
	landscapeRight,
	}

	/// Specifies a description of the application that is pertinent to the
	/// embedder's application switcher (also known as "recent tasks") user
	/// interface.
	///
	/// Used by [SystemChrome.setApplicationSwitcherDescription].
	@immutable
	class ApplicationSwitcherDescription {
	/// Creates an ApplicationSwitcherDescription.
	const ApplicationSwitcherDescription({ this.label, this.primaryColor });

	/// A label and description of the current state of the application.
	final String label;

	/// The application's primary color.
	///
	/// This may influence the color that the operating system uses to represent
	/// the application.
	final int primaryColor;
	}

	/// Specifies a system overlay at a particular location.
	///
	/// Used by [SystemChrome.setEnabledSystemUIOverlays].
	enum SystemUiOverlay {
	/// The status bar provided by the embedder on the top of the application
	/// surface, if any.
	top,

	/// The status bar provided by the embedder on the bottom of the application
	/// surface, if any.
	bottom,
	}

	/// Specifies a preference for the style of the system overlays.
	///
	/// Used by [SystemChrome.setSystemUIOverlayStyle].
	@immutable
	class SystemUiOverlayStyle {
	/// Creates a new [SystemUiOverlayStyle].
	const SystemUiOverlayStyle({
	this.systemNavigationBarColor,
	this.systemNavigationBarDividerColor,
	this.systemNavigationBarIconBrightness,
	this.statusBarColor,
	this.statusBarBrightness,
	this.statusBarIconBrightness,
	});

	/// The color of the system bottom navigation bar.
	///
	/// Only honored in Android versions O and greater.
	final Color systemNavigationBarColor;

	/// The color of the divider between the system's bottom navigation bar and the app's content.
	///
	/// Only honored in Android versions P and greater.
	final Color systemNavigationBarDividerColor;

	/// The brightness of the system navigation bar icons.
	///
	/// Only honored in Android versions O and greater.
	final Brightness systemNavigationBarIconBrightness;

	/// The color of top status bar.
	///
	/// Only honored in Android version M and greater.
	final Color statusBarColor;

	/// The brightness of top status bar.
	///
	/// Only honored in iOS.
	final Brightness statusBarBrightness;

	/// The brightness of the top status bar icons.
	///
	/// Only honored in Android version M and greater.
	final Brightness statusBarIconBrightness;

	/// System overlays should be drawn with a light color. Intended for
	/// applications with a dark background.
	static const SystemUiOverlayStyle light = SystemUiOverlayStyle(
	systemNavigationBarColor: Color(0xFF000000),
	systemNavigationBarDividerColor: null,
	statusBarColor: null,
	systemNavigationBarIconBrightness: Brightness.light,
	statusBarIconBrightness: Brightness.light,
	statusBarBrightness: Brightness.dark,
	);

	/// System overlays should be drawn with a dark color. Intended for
	/// applications with a light background.
	static const SystemUiOverlayStyle dark = SystemUiOverlayStyle(
	systemNavigationBarColor: Color(0xFF000000),
	systemNavigationBarDividerColor: null,
	statusBarColor: null,
	systemNavigationBarIconBrightness: Brightness.light,
	statusBarIconBrightness: Brightness.dark,
	statusBarBrightness: Brightness.light,
	);

	/// Convert this event to a map for serialization.
	Map<String, dynamic> _toMap() {
	return <String, dynamic>{
	'systemNavigationBarColor': systemNavigationBarColor?.value,
	'systemNavigationBarDividerColor': systemNavigationBarDividerColor?.value,
	'statusBarColor': statusBarColor?.value,
	'statusBarBrightness': statusBarBrightness?.toString(),
	'statusBarIconBrightness': statusBarIconBrightness?.toString(),
	'systemNavigationBarIconBrightness': systemNavigationBarIconBrightness?.toString(),
	};
	}

	@override
	String toString() => _toMap().toString();

	/// Creates a copy of this theme with the given fields replaced with new values.
	SystemUiOverlayStyle copyWith({
	Color systemNavigationBarColor,
	Color systemNavigationBarDividerColor,
	Color statusBarColor,
	Brightness statusBarBrightness,
	Brightness statusBarIconBrightness,
	Brightness systemNavigationBarIconBrightness,
	}) {
	return SystemUiOverlayStyle(
	systemNavigationBarColor: systemNavigationBarColor ?? this.systemNavigationBarColor,
	systemNavigationBarDividerColor: systemNavigationBarDividerColor ?? this.systemNavigationBarDividerColor,
	statusBarColor: statusBarColor ?? this.statusBarColor,
	statusBarIconBrightness: statusBarIconBrightness ?? this.statusBarIconBrightness,
	statusBarBrightness: statusBarBrightness ?? this.statusBarBrightness,
	systemNavigationBarIconBrightness: systemNavigationBarIconBrightness ?? this.systemNavigationBarIconBrightness,
	);
	}

	@override
	int get hashCode {
	return hashValues(
	systemNavigationBarColor,
	systemNavigationBarDividerColor,
	statusBarColor,
	statusBarBrightness,
	statusBarIconBrightness,
	systemNavigationBarIconBrightness,
	);
	}

	@override
	bool operator ==(Object other) {
	if (other.runtimeType != runtimeType)
	return false;
	return other is SystemUiOverlayStyle
	&& other.systemNavigationBarColor == systemNavigationBarColor
	&& other.systemNavigationBarDividerColor == systemNavigationBarDividerColor
	&& other.statusBarColor == statusBarColor
	&& other.statusBarIconBrightness == statusBarIconBrightness
	&& other.statusBarBrightness == statusBarBrightness
	&& other.systemNavigationBarIconBrightness == systemNavigationBarIconBrightness;
	}
	}

	List<String> _stringify(List<dynamic> list) => <String>[
	for (final dynamic item in list) item.toString(),
	];

	/// Controls specific aspects of the operating system's graphical interface and
	/// how it interacts with the application.
	class SystemChrome {
	// This class is not meant to be instatiated or extended; this constructor
	// prevents instantiation and extension.
	// ignore: unused_element
	SystemChrome._();

	/// Specifies the set of orientations the application interface can
	/// be displayed in.
	///
	/// The `orientation` argument is a list of [DeviceOrientation] enum values.
	/// The empty list causes the application to defer to the operating system
	/// default.
	///
	/// ## Limitations
	///
	/// This setting will only be respected on iPad if multitasking is disabled.
	///
	/// You can decide to opt out of multitasking on iPad, then
	/// setPreferredOrientations will work but your app will not
	/// support Slide Over and Split View multitasking anymore.
	///
	/// Should you decide to opt out of multitasking you can do this by
	/// setting "Requires full screen" to true in the Xcode Deployment Info.
	static Future<void> setPreferredOrientations(List<DeviceOrientation> orientations) async {
	await SystemChannels.platform.invokeMethod<void>(
	'SystemChrome.setPreferredOrientations',
	_stringify(orientations),
	);
	}

	/// Specifies the description of the current state of the application as it
	/// pertains to the application switcher (also known as "recent tasks").
	///
	/// Any part of the description that is unsupported on the current platform
	/// will be ignored.
	static Future<void> setApplicationSwitcherDescription(ApplicationSwitcherDescription description) async {
	await SystemChannels.platform.invokeMethod<void>(
	'SystemChrome.setApplicationSwitcherDescription',
	<String, dynamic>{
	'label': description.label,
	'primaryColor': description.primaryColor,
	},
	);
	}

	/// Specifies the set of system overlays to have visible when the application
	/// is running.
	///
	/// The `overlays` argument is a list of [SystemUiOverlay] enum values
	/// denoting the overlays to show.
	///
	/// If a particular overlay is unsupported on the platform, enabling or
	/// disabling that overlay will be ignored.
	///
	/// The settings here can be overridden by the platform when System UI becomes
	/// necessary for functionality.
	///
	/// For example, on Android, when the keyboard becomes visible, it will enable the
	/// navigation bar and status bar system UI overlays. When the keyboard is closed,
	/// Android will not restore the previous UI visibility settings, and the UI
	/// visibility cannot be changed until 1 second after the keyboard is closed to
	/// prevent malware locking users from navigation buttons.
	///
	/// To regain "fullscreen" after text entry, the UI overlays should be set again
	/// after a delay of 1 second. This can be achieved through [restoreSystemUIOverlays]
	/// or calling this again. Otherwise, the original UI overlay settings will be
	/// automatically restored only when the application loses and regains focus.
	static Future<void> setEnabledSystemUIOverlays(List<SystemUiOverlay> overlays) async {
	await SystemChannels.platform.invokeMethod<void>(
	'SystemChrome.setEnabledSystemUIOverlays',
	_stringify(overlays),
	);
	}

	/// Restores the system overlays to the last settings provided via
	/// [setEnabledSystemUIOverlays]. May be used when the platform force enables/disables
	/// UI elements.
	///
	/// For example, when the Android keyboard disables hidden status and navigation bars,
	/// this can be called to re-disable the bars when the keyboard is closed.
	///
	/// On Android, the system UI cannot be changed until 1 second after the previous
	/// change. This is to prevent malware from permanently hiding navigation buttons.
	static Future<void> restoreSystemUIOverlays() async {
	await SystemChannels.platform.invokeMethod<void>(
	'SystemChrome.restoreSystemUIOverlays',
	null,
	);
	}

	/// Specifies the style to use for the system overlays that are visible (if
	/// any).
	///
	/// This method will schedule the embedder update to be run in a microtask.
	/// Any subsequent calls to this method during the current event loop will
	/// overwrite the pending value, such that only the last specified value takes
	/// effect.
	///
	/// Call this API in code whose lifecycle matches that of the desired
	/// system UI styles. For instance, to change the system UI style on a new
	/// page, consider calling when pushing/popping a new [PageRoute].
	///
	/// However, the [AppBar] widget automatically sets the system overlay style
	/// based on its [AppBar.brightness], so configure that instead of calling
	/// this method directly. Likewise, do the same for [CupertinoNavigationBar]
	/// via [CupertinoNavigationBar.backgroundColor].
	///
	/// If a particular style is not supported on the platform, selecting it will
	/// have no effect.
	///
	/// {@tool snippet}
	/// ```dart
	/// @override
	/// Widget build(BuildContext context) {
	/// SystemChrome.setSystemUIOverlayStyle(SystemUiOverlayStyle.dark);
	/// return Placeholder();
	/// }
	/// ```
	/// {@end-tool}
	///
	/// For more complex control of the system overlay styles, consider using
	/// an [AnnotatedRegion] widget instead of calling [setSystemUiOverlayStyle]
	/// directly. This widget places a value directly into the layer tree where
	/// it can be hit-tested by the framework. On every frame, the framework will
	/// hit-test and select the annotated region it finds under the status and
	/// navigation bar and synthesize them into a single style. This can be used
	/// to configure the system styles when an app bar is not used.
	///
	/// {@tool sample --template=stateful_widget_material}
	/// The following example creates a widget that changes the status bar color
	/// to a random value on Android.
	///
	/// ```dart imports
	/// import 'package:flutter/services.dart';
	/// import 'dart:math' as math;
	/// ```
	///
	/// ```dart
	/// final _random = math.Random();
	/// SystemUiOverlayStyle _currentStyle = SystemUiOverlayStyle.light;
	///
	/// void _changeColor() {
	/// final color = Color.fromRGBO(
	/// _random.nextInt(255),
	/// _random.nextInt(255),
	/// _random.nextInt(255),
	/// 1.0,
	/// );
	/// setState(() {
	/// _currentStyle = SystemUiOverlayStyle.dark.copyWith(
	/// statusBarColor: color,
	/// );
	/// });
	/// }
	///
	/// @override
	/// Widget build(BuildContext context) {
	/// return AnnotatedRegion(
	/// value: _currentStyle,
	/// child: Center(
	/// child: RaisedButton(
	/// child: const Text('Change Color'),
	/// onPressed: _changeColor,
	/// ),
	/// ),
	/// );
	/// }
	/// ```
	/// {@end-tool}
	///
	/// See also:
	///
	/// * [AnnotatedRegion], the widget used to place data into the layer tree.
	static void setSystemUIOverlayStyle(SystemUiOverlayStyle style) {
	assert(style != null);
	if (_pendingStyle != null) {
	// The microtask has already been queued; just update the pending value.
	_pendingStyle = style;
	return;
	}
	if (style == _latestStyle) {
	// Trivial success: no microtask has been queued and the given style is
	// already in effect, so no need to queue a microtask.
	return;
	}
	_pendingStyle = style;
	scheduleMicrotask(() {
	assert(_pendingStyle != null);
	if (_pendingStyle != _latestStyle) {
	SystemChannels.platform.invokeMethod<void>(
	'SystemChrome.setSystemUIOverlayStyle',
	_pendingStyle._toMap(),
	);
	_latestStyle = _pendingStyle;
	}
	_pendingStyle = null;
	});
	}

	static SystemUiOverlayStyle _pendingStyle;

	/// The last style that was set using [SystemChrome.setSystemUIOverlayStyle].
	@visibleForTesting
	static SystemUiOverlayStyle get latestStyle => _latestStyle;
	static SystemUiOverlayStyle _latestStyle;
	}