packages/flutter/lib/src/material/switch_list_tile.dart - external/github.com/flutter/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 'package:flutter/widgets.dart';

 import 'list_tile.dart';
 import 'switch.dart';
 import 'theme.dart';
 import 'theme_data.dart';

 // Examples can assume:
 // void setState(VoidCallback fn) { }
 // bool _isSelected;

 enum _SwitchListTileType { material, adaptive }

 /// A [ListTile] with a [Switch]. In other words, a switch with a label.
 ///
 /// The entire list tile is interactive: tapping anywhere in the tile toggles
 /// the switch. Tapping and dragging the [Switch] also triggers the [onChanged]
 /// callback.
 ///
 /// To ensure that [onChanged] correctly triggers, the state passed
 /// into [value] must be properly managed. This is typically done by invoking
 /// [State.setState] in [onChanged] to toggle the state value.
 ///
 /// The [value], [onChanged], [activeColor], [activeThumbImage], and
 /// [inactiveThumbImage] properties of this widget are identical to the
 /// similarly-named properties on the [Switch] widget.
 ///
 /// The [title], [subtitle], [isThreeLine], and [dense] properties are like
 /// those of the same name on [ListTile].
 ///
 /// The [selected] property on this widget is similar to the [ListTile.selected]
 /// property, but the color used is that described by [activeColor], if any,
 /// defaulting to the accent color of the current [Theme]. No effort is made to
 /// coordinate the [selected] state and the [value] state; to have the list tile
 /// appear selected when the switch is on, pass the same value to both.
 ///
 /// The switch is shown on the right by default in left-to-right languages (i.e.
 /// in the [ListTile.trailing] slot) which can be changed using [controlAffinity].
 /// The [secondary] widget is placed in the [ListTile.leading] slot.
 ///
 /// To show the [SwitchListTile] as disabled, pass null as the [onChanged]
 /// callback.
 ///
 /// {@tool dartpad --template=stateful_widget_scaffold_center}
 ///
 /// ![SwitchListTile sample](https://flutter.github.io/assets-for-api-docs/assets/material/switch_list_tile.png)
 ///
 /// This widget shows a switch that, when toggled, changes the state of a [bool]
 /// member field called `_lights`.
 ///
 /// ```dart
 /// bool _lights = false;
 ///
 /// @override
 /// Widget build(BuildContext context) {
 ///   return SwitchListTile(
 ///     title: const Text('Lights'),
 ///     value: _lights,
 ///     onChanged: (bool value) { setState(() { _lights = value; }); },
 ///     secondary: const Icon(Icons.lightbulb_outline),
 ///   );
 /// }
 /// ```
 /// {@end-tool}
 ///
 /// ## Semantics in SwitchListTile
 ///
 /// Since the entirety of the SwitchListTile is interactive, it should represent
 /// itself as a single interactive entity.
 ///
 /// To do so, a SwitchListTile widget wraps its children with a [MergeSemantics]
 /// widget. [MergeSemantics] will attempt to merge its descendant [Semantics]
 /// nodes into one node in the semantics tree. Therefore, SwitchListTile will
 /// throw an error if any of its children requires its own [Semantics] node.
 ///
 /// For example, you cannot nest a [RichText] widget as a descendant of
 /// SwitchListTile. [RichText] has an embedded gesture recognizer that
 /// requires its own [Semantics] node, which directly conflicts with
 /// SwitchListTile's desire to merge all its descendants' semantic nodes
 /// into one. Therefore, it may be necessary to create a custom radio tile
 /// widget to accommodate similar use cases.
 ///
 /// {@tool dartpad --template=stateful_widget_scaffold_center}
 ///
 /// ![Switch list tile semantics sample](https://flutter.github.io/assets-for-api-docs/assets/material/switch_list_tile_semantics.png)
 ///
 /// Here is an example of a custom labeled radio widget, called
 /// LinkedLabelRadio, that includes an interactive [RichText] widget that
 /// handles tap gestures.
 ///
 /// ```dart imports
 /// import 'package:flutter/gestures.dart';
 /// ```
 /// ```dart preamble
 /// class LinkedLabelSwitch extends StatelessWidget {
 ///   const LinkedLabelSwitch({
 ///     required this.label,
 ///     required this.padding,
 ///     required this.value,
 ///     required this.onChanged,
 ///   });
 ///
 ///   final String label;
 ///   final EdgeInsets padding;
 ///   final bool value;
 ///   final Function onChanged;
 ///
 ///   @override
 ///   Widget build(BuildContext context) {
 ///     return Padding(
 ///       padding: padding,
 ///       child: Row(
 ///         children: <Widget>[
 ///           Expanded(
 ///             child: RichText(
 ///               text: TextSpan(
 ///                 text: label,
 ///                 style: TextStyle(
 ///                   color: Colors.blueAccent,
 ///                   decoration: TextDecoration.underline,
 ///                 ),
 ///                 recognizer: TapGestureRecognizer()
 ///                   ..onTap = () {
 ///                   print('Label has been tapped.');
 ///                 },
 ///               ),
 ///             ),
 ///           ),
 ///           Switch(
 ///             value: value,
 ///             onChanged: (bool newValue) {
 ///               onChanged(newValue);
 ///             },
 ///           ),
 ///         ],
 ///       ),
 ///     );
 ///   }
 /// }
 /// ```
 /// ```dart
 /// bool _isSelected = false;
 ///
 /// @override
 /// Widget build(BuildContext context) {
 ///   return LinkedLabelSwitch(
 ///     label: 'Linked, tappable label text',
 ///     padding: const EdgeInsets.symmetric(horizontal: 20.0),
 ///     value: _isSelected,
 ///     onChanged: (bool newValue) {
 ///       setState(() {
 ///         _isSelected = newValue;
 ///       });
 ///     },
 ///   );
 /// }
 /// ```
 /// {@end-tool}
 ///
 /// ## SwitchListTile isn't exactly what I want
 ///
 /// If the way SwitchListTile pads and positions its elements isn't quite what
 /// you're looking for, you can create custom labeled switch widgets by
 /// combining [Switch] with other widgets, such as [Text], [Padding] and
 /// [InkWell].
 ///
 /// {@tool dartpad --template=stateful_widget_scaffold_center}
 ///
 /// ![Custom switch list tile sample](https://flutter.github.io/assets-for-api-docs/assets/material/switch_list_tile_custom.png)
 ///
 /// Here is an example of a custom LabeledSwitch widget, but you can easily
 /// make your own configurable widget.
 ///
 /// ```dart preamble
 /// class LabeledSwitch extends StatelessWidget {
 ///   const LabeledSwitch({
 ///     required this.label,
 ///     required this.padding,
 ///     required this.value,
 ///     required this.onChanged,
 ///   });
 ///
 ///   final String label;
 ///   final EdgeInsets padding;
 ///   final bool value;
 ///   final Function onChanged;
 ///
 ///   @override
 ///   Widget build(BuildContext context) {
 ///     return InkWell(
 ///       onTap: () {
 ///         onChanged(!value);
 ///       },
 ///       child: Padding(
 ///         padding: padding,
 ///         child: Row(
 ///           children: <Widget>[
 ///             Expanded(child: Text(label)),
 ///             Switch(
 ///               value: value,
 ///               onChanged: (bool newValue) {
 ///                 onChanged(newValue);
 ///               },
 ///             ),
 ///           ],
 ///         ),
 ///       ),
 ///     );
 ///   }
 /// }
 /// ```
 /// ```dart
 /// bool _isSelected = false;
 ///
 /// @override
 /// Widget build(BuildContext context) {
 ///   return LabeledSwitch(
 ///     label: 'This is the label text',
 ///     padding: const EdgeInsets.symmetric(horizontal: 20.0),
 ///     value: _isSelected,
 ///     onChanged: (bool newValue) {
 ///       setState(() {
 ///         _isSelected = newValue;
 ///       });
 ///     },
 ///   );
 /// }
 /// ```
 /// {@end-tool}
 ///
 /// See also:
 ///
 ///  * [ListTileTheme], which can be used to affect the style of list tiles,
 ///    including switch list tiles.
 ///  * [CheckboxListTile], a similar widget for checkboxes.
 ///  * [RadioListTile], a similar widget for radio buttons.
 ///  * [ListTile] and [Switch], the widgets from which this widget is made.
 class SwitchListTile extends StatelessWidget {
   /// Creates a combination of a list tile and a switch.
   ///
   /// The switch tile itself does not maintain any state. Instead, when the
   /// state of the switch changes, the widget calls the [onChanged] callback.
   /// Most widgets that use a switch will listen for the [onChanged] callback
   /// and rebuild the switch tile with a new [value] to update the visual
   /// appearance of the switch.
   ///
   /// The following arguments are required:
   ///
   /// * [value] determines whether this switch is on or off.
   /// * [onChanged] is called when the user toggles the switch on or off.
   const SwitchListTile({
     Key? key,
     required this.value,
     required this.onChanged,
     this.tileColor,
     this.activeColor,
     this.activeTrackColor,
     this.inactiveThumbColor,
     this.inactiveTrackColor,
     this.activeThumbImage,
     this.inactiveThumbImage,
     this.title,
     this.subtitle,
     this.isThreeLine = false,
     this.dense,
     this.contentPadding,
     this.secondary,
     this.selected = false,
     this.autofocus = false,
     this.controlAffinity = ListTileControlAffinity.platform,
     this.shape,
     this.selectedTileColor,
   }) : _switchListTileType = _SwitchListTileType.material,
        assert(value != null),
        assert(isThreeLine != null),
        assert(!isThreeLine || subtitle != null),
        assert(selected != null),
        assert(autofocus != null),
        super(key: key);

   /// Creates a Material [ListTile] with an adaptive [Switch], following
   /// Material design's
   /// [Cross-platform guidelines](https://material.io/design/platform-guidance/cross-platform-adaptation.html).
   ///
   /// This widget uses [Switch.adaptive] to change the graphics of the switch
   /// component based on the ambient [ThemeData.platform]. On iOS and macOS, a
   /// [CupertinoSwitch] will be used. On other platforms a Material design
   /// [Switch] will be used.
   ///
   /// If a [CupertinoSwitch] is created, the following parameters are
   /// ignored: [activeTrackColor], [inactiveThumbColor], [inactiveTrackColor],
   /// [activeThumbImage], [inactiveThumbImage].
   const SwitchListTile.adaptive({
     Key? key,
     required this.value,
     required this.onChanged,
     this.tileColor,
     this.activeColor,
     this.activeTrackColor,
     this.inactiveThumbColor,
     this.inactiveTrackColor,
     this.activeThumbImage,
     this.inactiveThumbImage,
     this.title,
     this.subtitle,
     this.isThreeLine = false,
     this.dense,
     this.contentPadding,
     this.secondary,
     this.selected = false,
     this.autofocus = false,
     this.controlAffinity = ListTileControlAffinity.platform,
     this.shape,
     this.selectedTileColor,
   }) : _switchListTileType = _SwitchListTileType.adaptive,
        assert(value != null),
        assert(isThreeLine != null),
        assert(!isThreeLine || subtitle != null),
        assert(selected != null),
        assert(autofocus != null),
        super(key: key);

   /// Whether this switch is checked.
   ///
   /// This property must not be null.
   final bool value;

   /// Called when the user toggles the switch on or off.
   ///
   /// The switch passes the new value to the callback but does not actually
   /// change state until the parent widget rebuilds the switch tile with the
   /// new value.
   ///
   /// If null, the switch will be displayed as disabled.
   ///
   /// The callback provided to [onChanged] should update the state of the parent
   /// [StatefulWidget] using the [State.setState] method, so that the parent
   /// gets rebuilt; for example:
   ///
   /// ```dart
   /// SwitchListTile(
   ///   value: _isSelected,
   ///   onChanged: (bool newValue) {
   ///     setState(() {
   ///       _isSelected = newValue;
   ///     });
   ///   },
   ///   title: Text('Selection'),
   /// )
   /// ```
   final ValueChanged<bool>? onChanged;

   /// The color to use when this switch is on.
   ///
   /// Defaults to accent color of the current [Theme].
   final Color? activeColor;

   /// The color to use on the track when this switch is on.
   ///
   /// Defaults to [ThemeData.toggleableActiveColor] with the opacity set at 50%.
   ///
   /// Ignored if created with [SwitchListTile.adaptive].
   final Color? activeTrackColor;

   /// The color to use on the thumb when this switch is off.
   ///
   /// Defaults to the colors described in the Material design specification.
   ///
   /// Ignored if created with [SwitchListTile.adaptive].
   final Color? inactiveThumbColor;

   /// The color to use on the track when this switch is off.
   ///
   /// Defaults to the colors described in the Material design specification.
   ///
   /// Ignored if created with [SwitchListTile.adaptive].
   final Color? inactiveTrackColor;

   /// {@macro flutter.material.ListTile.tileColor}
   final Color? tileColor;

   /// An image to use on the thumb of this switch when the switch is on.
   final ImageProvider? activeThumbImage;

   /// An image to use on the thumb of this switch when the switch is off.
   ///
   /// Ignored if created with [SwitchListTile.adaptive].
   final ImageProvider? inactiveThumbImage;

   /// The primary content of the list tile.
   ///
   /// Typically a [Text] widget.
   final Widget? title;

   /// Additional content displayed below the title.
   ///
   /// Typically a [Text] widget.
   final Widget? subtitle;

   /// A widget to display on the opposite side of the tile from the switch.
   ///
   /// Typically an [Icon] widget.
   final Widget? secondary;

   /// Whether this list tile is intended to display three lines of text.
   ///
   /// If false, the list tile is treated as having one line if the subtitle is
   /// null and treated as having two lines if the subtitle is non-null.
   final bool isThreeLine;

   /// Whether this list tile is part of a vertically dense list.
   ///
   /// If this property is null then its value is based on [ListTileTheme.dense].
   final bool? dense;

   /// The tile's internal padding.
   ///
   /// Insets a [SwitchListTile]'s contents: its [title], [subtitle],
   /// [secondary], and [Switch] widgets.
   ///
   /// If null, [ListTile]'s default of `EdgeInsets.symmetric(horizontal: 16.0)`
   /// is used.
   final EdgeInsetsGeometry? contentPadding;

   /// Whether to render icons and text in the [activeColor].
   ///
   /// No effort is made to automatically coordinate the [selected] state and the
   /// [value] state. To have the list tile appear selected when the switch is
   /// on, pass the same value to both.
   ///
   /// Normally, this property is left to its default value, false.
   final bool selected;

   /// {@macro flutter.widgets.Focus.autofocus}
   final bool autofocus;

   /// If adaptive, creates the switch with [Switch.adaptive].
   final _SwitchListTileType _switchListTileType;

   /// Defines the position of control and [secondary], relative to text.
   ///
   /// By default, the value of `controlAffinity` is [ListTileControlAffinity.platform].
   final ListTileControlAffinity controlAffinity;

   /// {@macro flutter.material.ListTileTheme.shape}
   final ShapeBorder? shape;

   /// If non-null, defines the background color when [SwitchListTile.selected] is true.
   final Color? selectedTileColor;

   @override
   Widget build(BuildContext context) {
     final Widget control;
     switch (_switchListTileType) {
       case _SwitchListTileType.adaptive:
         control = Switch.adaptive(
           value: value,
           onChanged: onChanged,
           activeColor: activeColor,
           activeThumbImage: activeThumbImage,
           inactiveThumbImage: inactiveThumbImage,
           materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
           activeTrackColor: activeTrackColor,
           inactiveTrackColor: inactiveTrackColor,
           inactiveThumbColor: inactiveThumbColor,
           autofocus: autofocus,
         );
         break;

       case _SwitchListTileType.material:
         control = Switch(
           value: value,
           onChanged: onChanged,
           activeColor: activeColor,
           activeThumbImage: activeThumbImage,
           inactiveThumbImage: inactiveThumbImage,
           materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
           activeTrackColor: activeTrackColor,
           inactiveTrackColor: inactiveTrackColor,
           inactiveThumbColor: inactiveThumbColor,
           autofocus: autofocus,
         );
     }

     Widget? leading, trailing;
     switch (controlAffinity) {
       case ListTileControlAffinity.leading:
         leading = control;
         trailing = secondary;
         break;
       case ListTileControlAffinity.trailing:
       case ListTileControlAffinity.platform:
         leading = secondary;
         trailing = control;
         break;
     }

     return MergeSemantics(
       child: ListTileTheme.merge(
         selectedColor: activeColor ?? Theme.of(context).accentColor,
         child: ListTile(
           leading: leading,
           title: title,
           subtitle: subtitle,
           trailing: trailing,
           isThreeLine: isThreeLine,
           dense: dense,
           contentPadding: contentPadding,
           enabled: onChanged != null,
           onTap: onChanged != null ? () { onChanged!(!value); } : null,
           selected: selected,
           selectedTileColor: selectedTileColor,
           autofocus: autofocus,
           shape: shape,
           tileColor: tileColor,
         ),
       ),
     );
   }
 }
	// 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 'package:flutter/widgets.dart';

	import 'list_tile.dart';
	import 'switch.dart';
	import 'theme.dart';
	import 'theme_data.dart';

	// Examples can assume:
	// void setState(VoidCallback fn) { }
	// bool _isSelected;

	enum _SwitchListTileType { material, adaptive }

	/// A [ListTile] with a [Switch]. In other words, a switch with a label.
	///
	/// The entire list tile is interactive: tapping anywhere in the tile toggles
	/// the switch. Tapping and dragging the [Switch] also triggers the [onChanged]
	/// callback.
	///
	/// To ensure that [onChanged] correctly triggers, the state passed
	/// into [value] must be properly managed. This is typically done by invoking
	/// [State.setState] in [onChanged] to toggle the state value.
	///
	/// The [value], [onChanged], [activeColor], [activeThumbImage], and
	/// [inactiveThumbImage] properties of this widget are identical to the
	/// similarly-named properties on the [Switch] widget.
	///
	/// The [title], [subtitle], [isThreeLine], and [dense] properties are like
	/// those of the same name on [ListTile].
	///
	/// The [selected] property on this widget is similar to the [ListTile.selected]
	/// property, but the color used is that described by [activeColor], if any,
	/// defaulting to the accent color of the current [Theme]. No effort is made to
	/// coordinate the [selected] state and the [value] state; to have the list tile
	/// appear selected when the switch is on, pass the same value to both.
	///
	/// The switch is shown on the right by default in left-to-right languages (i.e.
	/// in the [ListTile.trailing] slot) which can be changed using [controlAffinity].
	/// The [secondary] widget is placed in the [ListTile.leading] slot.
	///
	/// To show the [SwitchListTile] as disabled, pass null as the [onChanged]
	/// callback.
	///
	/// {@tool dartpad --template=stateful_widget_scaffold_center}
	///
	/// ![SwitchListTile sample](https://flutter.github.io/assets-for-api-docs/assets/material/switch_list_tile.png)
	///
	/// This widget shows a switch that, when toggled, changes the state of a [bool]
	/// member field called `_lights`.
	///
	/// ```dart
	/// bool _lights = false;
	///
	/// @override
	/// Widget build(BuildContext context) {
	/// return SwitchListTile(
	/// title: const Text('Lights'),
	/// value: _lights,
	/// onChanged: (bool value) { setState(() { _lights = value; }); },
	/// secondary: const Icon(Icons.lightbulb_outline),
	/// );
	/// }
	/// ```
	/// {@end-tool}
	///
	/// ## Semantics in SwitchListTile
	///
	/// Since the entirety of the SwitchListTile is interactive, it should represent
	/// itself as a single interactive entity.
	///
	/// To do so, a SwitchListTile widget wraps its children with a [MergeSemantics]
	/// widget. [MergeSemantics] will attempt to merge its descendant [Semantics]
	/// nodes into one node in the semantics tree. Therefore, SwitchListTile will
	/// throw an error if any of its children requires its own [Semantics] node.
	///
	/// For example, you cannot nest a [RichText] widget as a descendant of
	/// SwitchListTile. [RichText] has an embedded gesture recognizer that
	/// requires its own [Semantics] node, which directly conflicts with
	/// SwitchListTile's desire to merge all its descendants' semantic nodes
	/// into one. Therefore, it may be necessary to create a custom radio tile
	/// widget to accommodate similar use cases.
	///
	/// {@tool dartpad --template=stateful_widget_scaffold_center}
	///
	/// ![Switch list tile semantics sample](https://flutter.github.io/assets-for-api-docs/assets/material/switch_list_tile_semantics.png)
	///
	/// Here is an example of a custom labeled radio widget, called
	/// LinkedLabelRadio, that includes an interactive [RichText] widget that
	/// handles tap gestures.
	///
	/// ```dart imports
	/// import 'package:flutter/gestures.dart';
	/// ```
	/// ```dart preamble
	/// class LinkedLabelSwitch extends StatelessWidget {
	/// const LinkedLabelSwitch({
	/// required this.label,
	/// required this.padding,
	/// required this.value,
	/// required this.onChanged,
	/// });
	///
	/// final String label;
	/// final EdgeInsets padding;
	/// final bool value;
	/// final Function onChanged;
	///
	/// @override
	/// Widget build(BuildContext context) {
	/// return Padding(
	/// padding: padding,
	/// child: Row(
	/// children: <Widget>[
	/// Expanded(
	/// child: RichText(
	/// text: TextSpan(
	/// text: label,
	/// style: TextStyle(
	/// color: Colors.blueAccent,
	/// decoration: TextDecoration.underline,
	/// ),
	/// recognizer: TapGestureRecognizer()
	/// ..onTap = () {
	/// print('Label has been tapped.');
	/// },
	/// ),
	/// ),
	/// ),
	/// Switch(
	/// value: value,
	/// onChanged: (bool newValue) {
	/// onChanged(newValue);
	/// },
	/// ),
	/// ],
	/// ),
	/// );
	/// }
	/// }
	/// ```
	/// ```dart
	/// bool _isSelected = false;
	///
	/// @override
	/// Widget build(BuildContext context) {
	/// return LinkedLabelSwitch(
	/// label: 'Linked, tappable label text',
	/// padding: const EdgeInsets.symmetric(horizontal: 20.0),
	/// value: _isSelected,
	/// onChanged: (bool newValue) {
	/// setState(() {
	/// _isSelected = newValue;
	/// });
	/// },
	/// );
	/// }
	/// ```
	/// {@end-tool}
	///
	/// ## SwitchListTile isn't exactly what I want
	///
	/// If the way SwitchListTile pads and positions its elements isn't quite what
	/// you're looking for, you can create custom labeled switch widgets by
	/// combining [Switch] with other widgets, such as [Text], [Padding] and
	/// [InkWell].
	///
	/// {@tool dartpad --template=stateful_widget_scaffold_center}
	///
	/// ![Custom switch list tile sample](https://flutter.github.io/assets-for-api-docs/assets/material/switch_list_tile_custom.png)
	///
	/// Here is an example of a custom LabeledSwitch widget, but you can easily
	/// make your own configurable widget.
	///
	/// ```dart preamble
	/// class LabeledSwitch extends StatelessWidget {
	/// const LabeledSwitch({
	/// required this.label,
	/// required this.padding,
	/// required this.value,
	/// required this.onChanged,
	/// });
	///
	/// final String label;
	/// final EdgeInsets padding;
	/// final bool value;
	/// final Function onChanged;
	///
	/// @override
	/// Widget build(BuildContext context) {
	/// return InkWell(
	/// onTap: () {
	/// onChanged(!value);
	/// },
	/// child: Padding(
	/// padding: padding,
	/// child: Row(
	/// children: <Widget>[
	/// Expanded(child: Text(label)),
	/// Switch(
	/// value: value,
	/// onChanged: (bool newValue) {
	/// onChanged(newValue);
	/// },
	/// ),
	/// ],
	/// ),
	/// ),
	/// );
	/// }
	/// }
	/// ```
	/// ```dart
	/// bool _isSelected = false;
	///
	/// @override
	/// Widget build(BuildContext context) {
	/// return LabeledSwitch(
	/// label: 'This is the label text',
	/// padding: const EdgeInsets.symmetric(horizontal: 20.0),
	/// value: _isSelected,
	/// onChanged: (bool newValue) {
	/// setState(() {
	/// _isSelected = newValue;
	/// });
	/// },
	/// );
	/// }
	/// ```
	/// {@end-tool}
	///
	/// See also:
	///
	/// * [ListTileTheme], which can be used to affect the style of list tiles,
	/// including switch list tiles.
	/// * [CheckboxListTile], a similar widget for checkboxes.
	/// * [RadioListTile], a similar widget for radio buttons.
	/// * [ListTile] and [Switch], the widgets from which this widget is made.
	class SwitchListTile extends StatelessWidget {
	/// Creates a combination of a list tile and a switch.
	///
	/// The switch tile itself does not maintain any state. Instead, when the
	/// state of the switch changes, the widget calls the [onChanged] callback.
	/// Most widgets that use a switch will listen for the [onChanged] callback
	/// and rebuild the switch tile with a new [value] to update the visual
	/// appearance of the switch.
	///
	/// The following arguments are required:
	///
	/// * [value] determines whether this switch is on or off.
	/// * [onChanged] is called when the user toggles the switch on or off.
	const SwitchListTile({
	Key? key,
	required this.value,
	required this.onChanged,
	this.tileColor,
	this.activeColor,
	this.activeTrackColor,
	this.inactiveThumbColor,
	this.inactiveTrackColor,
	this.activeThumbImage,
	this.inactiveThumbImage,
	this.title,
	this.subtitle,
	this.isThreeLine = false,
	this.dense,
	this.contentPadding,
	this.secondary,
	this.selected = false,
	this.autofocus = false,
	this.controlAffinity = ListTileControlAffinity.platform,
	this.shape,
	this.selectedTileColor,
	}) : _switchListTileType = _SwitchListTileType.material,
	assert(value != null),
	assert(isThreeLine != null),
	assert(!isThreeLine \|\| subtitle != null),
	assert(selected != null),
	assert(autofocus != null),
	super(key: key);

	/// Creates a Material [ListTile] with an adaptive [Switch], following
	/// Material design's
	/// [Cross-platform guidelines](https://material.io/design/platform-guidance/cross-platform-adaptation.html).
	///
	/// This widget uses [Switch.adaptive] to change the graphics of the switch
	/// component based on the ambient [ThemeData.platform]. On iOS and macOS, a
	/// [CupertinoSwitch] will be used. On other platforms a Material design
	/// [Switch] will be used.
	///
	/// If a [CupertinoSwitch] is created, the following parameters are
	/// ignored: [activeTrackColor], [inactiveThumbColor], [inactiveTrackColor],
	/// [activeThumbImage], [inactiveThumbImage].
	const SwitchListTile.adaptive({
	Key? key,
	required this.value,
	required this.onChanged,
	this.tileColor,
	this.activeColor,
	this.activeTrackColor,
	this.inactiveThumbColor,
	this.inactiveTrackColor,
	this.activeThumbImage,
	this.inactiveThumbImage,
	this.title,
	this.subtitle,
	this.isThreeLine = false,
	this.dense,
	this.contentPadding,
	this.secondary,
	this.selected = false,
	this.autofocus = false,
	this.controlAffinity = ListTileControlAffinity.platform,
	this.shape,
	this.selectedTileColor,
	}) : _switchListTileType = _SwitchListTileType.adaptive,
	assert(value != null),
	assert(isThreeLine != null),
	assert(!isThreeLine \|\| subtitle != null),
	assert(selected != null),
	assert(autofocus != null),
	super(key: key);

	/// Whether this switch is checked.
	///
	/// This property must not be null.
	final bool value;

	/// Called when the user toggles the switch on or off.
	///
	/// The switch passes the new value to the callback but does not actually
	/// change state until the parent widget rebuilds the switch tile with the
	/// new value.
	///
	/// If null, the switch will be displayed as disabled.
	///
	/// The callback provided to [onChanged] should update the state of the parent
	/// [StatefulWidget] using the [State.setState] method, so that the parent
	/// gets rebuilt; for example:
	///
	/// ```dart
	/// SwitchListTile(
	/// value: _isSelected,
	/// onChanged: (bool newValue) {
	/// setState(() {
	/// _isSelected = newValue;
	/// });
	/// },
	/// title: Text('Selection'),
	/// )
	/// ```
	final ValueChanged<bool>? onChanged;

	/// The color to use when this switch is on.
	///
	/// Defaults to accent color of the current [Theme].
	final Color? activeColor;

	/// The color to use on the track when this switch is on.
	///
	/// Defaults to [ThemeData.toggleableActiveColor] with the opacity set at 50%.
	///
	/// Ignored if created with [SwitchListTile.adaptive].
	final Color? activeTrackColor;

	/// The color to use on the thumb when this switch is off.
	///
	/// Defaults to the colors described in the Material design specification.
	///
	/// Ignored if created with [SwitchListTile.adaptive].
	final Color? inactiveThumbColor;

	/// The color to use on the track when this switch is off.
	///
	/// Defaults to the colors described in the Material design specification.
	///
	/// Ignored if created with [SwitchListTile.adaptive].
	final Color? inactiveTrackColor;

	/// {@macro flutter.material.ListTile.tileColor}
	final Color? tileColor;

	/// An image to use on the thumb of this switch when the switch is on.
	final ImageProvider? activeThumbImage;

	/// An image to use on the thumb of this switch when the switch is off.
	///
	/// Ignored if created with [SwitchListTile.adaptive].
	final ImageProvider? inactiveThumbImage;

	/// The primary content of the list tile.
	///
	/// Typically a [Text] widget.
	final Widget? title;

	/// Additional content displayed below the title.
	///
	/// Typically a [Text] widget.
	final Widget? subtitle;

	/// A widget to display on the opposite side of the tile from the switch.
	///
	/// Typically an [Icon] widget.
	final Widget? secondary;

	/// Whether this list tile is intended to display three lines of text.
	///
	/// If false, the list tile is treated as having one line if the subtitle is
	/// null and treated as having two lines if the subtitle is non-null.
	final bool isThreeLine;

	/// Whether this list tile is part of a vertically dense list.
	///
	/// If this property is null then its value is based on [ListTileTheme.dense].
	final bool? dense;

	/// The tile's internal padding.
	///
	/// Insets a [SwitchListTile]'s contents: its [title], [subtitle],
	/// [secondary], and [Switch] widgets.
	///
	/// If null, [ListTile]'s default of `EdgeInsets.symmetric(horizontal: 16.0)`
	/// is used.
	final EdgeInsetsGeometry? contentPadding;

	/// Whether to render icons and text in the [activeColor].
	///
	/// No effort is made to automatically coordinate the [selected] state and the
	/// [value] state. To have the list tile appear selected when the switch is
	/// on, pass the same value to both.
	///
	/// Normally, this property is left to its default value, false.
	final bool selected;

	/// {@macro flutter.widgets.Focus.autofocus}
	final bool autofocus;

	/// If adaptive, creates the switch with [Switch.adaptive].
	final _SwitchListTileType _switchListTileType;

	/// Defines the position of control and [secondary], relative to text.
	///
	/// By default, the value of `controlAffinity` is [ListTileControlAffinity.platform].
	final ListTileControlAffinity controlAffinity;

	/// {@macro flutter.material.ListTileTheme.shape}
	final ShapeBorder? shape;

	/// If non-null, defines the background color when [SwitchListTile.selected] is true.
	final Color? selectedTileColor;

	@override
	Widget build(BuildContext context) {
	final Widget control;
	switch (_switchListTileType) {
	case _SwitchListTileType.adaptive:
	control = Switch.adaptive(
	value: value,
	onChanged: onChanged,
	activeColor: activeColor,
	activeThumbImage: activeThumbImage,
	inactiveThumbImage: inactiveThumbImage,
	materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
	activeTrackColor: activeTrackColor,
	inactiveTrackColor: inactiveTrackColor,
	inactiveThumbColor: inactiveThumbColor,
	autofocus: autofocus,
	);
	break;

	case _SwitchListTileType.material:
	control = Switch(
	value: value,
	onChanged: onChanged,
	activeColor: activeColor,
	activeThumbImage: activeThumbImage,
	inactiveThumbImage: inactiveThumbImage,
	materialTapTargetSize: MaterialTapTargetSize.shrinkWrap,
	activeTrackColor: activeTrackColor,
	inactiveTrackColor: inactiveTrackColor,
	inactiveThumbColor: inactiveThumbColor,
	autofocus: autofocus,
	);
	}

	Widget? leading, trailing;
	switch (controlAffinity) {
	case ListTileControlAffinity.leading:
	leading = control;
	trailing = secondary;
	break;
	case ListTileControlAffinity.trailing:
	case ListTileControlAffinity.platform:
	leading = secondary;
	trailing = control;
	break;
	}

	return MergeSemantics(
	child: ListTileTheme.merge(
	selectedColor: activeColor ?? Theme.of(context).accentColor,
	child: ListTile(
	leading: leading,
	title: title,
	subtitle: subtitle,
	trailing: trailing,
	isThreeLine: isThreeLine,
	dense: dense,
	contentPadding: contentPadding,
	enabled: onChanged != null,
	onTap: onChanged != null ? () { onChanged!(!value); } : null,
	selected: selected,
	selectedTileColor: selectedTileColor,
	autofocus: autofocus,
	shape: shape,
	tileColor: tileColor,
	),
	),
	);
	}
	}