switch_list_tile.dart

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

import 'list_tile.dart';
import 'list_tile_theme.dart';
import 'material_state.dart';
import 'switch.dart';
import 'switch_theme.dart';
import 'theme.dart';
import 'theme_data.dart';

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

enum _SwitchListTileType { material, adaptive }

/// A [ListTile] with a [Switch]. In other words, a switch with a label.
///
/// {@youtube 560 315 https://www.youtube.com/watch?v=0igIjvtEWNU}
///
/// 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. This tile's [activeColor] is used for the selected item's text color, or
/// the theme's [SwitchThemeData.overlayColor] if [activeColor] is null.
///
/// This widget does not coordinate the [selected] state and the
/// [value]; to have the list tile appear selected when the
/// switch button is on, use the same value for 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.
///
/// This widget requires a [Material] widget ancestor in the tree to paint
/// itself on, which is typically provided by the app's [Scaffold].
/// The [tileColor], and [selectedTileColor] are not painted by the
/// [SwitchListTile] itself but by the [Material] widget ancestor. In this
/// case, one can wrap a [Material] widget around the [SwitchListTile], e.g.:
///
/// {@tool snippet}
/// ```dart
/// ColoredBox(
///   color: Colors.green,
///   child: Material(
///     child: SwitchListTile(
///       tileColor: Colors.red,
///       title: const Text('SwitchListTile with red background'),
///       value: true,
///       onChanged:(bool? value) { },
///     ),
///   ),
/// )
/// ```
/// {@end-tool}
///
/// ## Performance considerations when wrapping [SwitchListTile] with [Material]
///
/// Wrapping a large number of [SwitchListTile]s individually with [Material]s
/// is expensive. Consider only wrapping the [SwitchListTile]s that require it
/// or include a common [Material] ancestor where possible.
///
/// To show the [SwitchListTile] as disabled, pass null as the [onChanged]
/// callback.
///
/// {@tool dartpad}
/// ![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`.
///
/// ** See code in examples/api/lib/material/switch_list_tile/switch_list_tile.0.dart **
/// {@end-tool}
///
/// {@tool dartpad}
/// This sample demonstrates how [SwitchListTile] positions the switch widget
/// relative to the text in different configurations.
///
/// ** See code in examples/api/lib/material/switch_list_tile/switch_list_tile.1.dart **
/// {@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}
/// ![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.
///
/// ** See code in examples/api/lib/material/switch_list_tile/custom_labeled_switch.0.dart **
/// {@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}
/// ![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.
///
/// ** See code in examples/api/lib/material/switch_list_tile/custom_labeled_switch.1.dart **
/// {@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({
    super.key,
    required this.value,
    required this.onChanged,
    this.activeColor,
    this.activeTrackColor,
    this.inactiveThumbColor,
    this.inactiveTrackColor,
    this.activeThumbImage,
    this.onActiveThumbImageError,
    this.inactiveThumbImage,
    this.onInactiveThumbImageError,
    this.thumbColor,
    this.trackColor,
    this.trackOutlineColor,
    this.thumbIcon,
    this.materialTapTargetSize,
    this.dragStartBehavior = DragStartBehavior.start,
    this.mouseCursor,
    this.overlayColor,
    this.splashRadius,
    this.focusNode,
    this.onFocusChange,
    this.autofocus = false,
    this.tileColor,
    this.title,
    this.subtitle,
    this.isThreeLine = false,
    this.dense,
    this.contentPadding,
    this.secondary,
    this.selected = false,
    this.controlAffinity = ListTileControlAffinity.platform,
    this.shape,
    this.selectedTileColor,
    this.visualDensity,
    this.enableFeedback,
    this.hoverColor,
  }) : _switchListTileType = _SwitchListTileType.material,
       applyCupertinoTheme = false,
       assert(activeThumbImage != null || onActiveThumbImageError == null),
       assert(inactiveThumbImage != null || onInactiveThumbImageError == null),
       assert(!isThreeLine || subtitle != null);

  /// 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({
    super.key,
    required this.value,
    required this.onChanged,
    this.activeColor,
    this.activeTrackColor,
    this.inactiveThumbColor,
    this.inactiveTrackColor,
    this.activeThumbImage,
    this.onActiveThumbImageError,
    this.inactiveThumbImage,
    this.onInactiveThumbImageError,
    this.thumbColor,
    this.trackColor,
    this.trackOutlineColor,
    this.thumbIcon,
    this.materialTapTargetSize,
    this.dragStartBehavior = DragStartBehavior.start,
    this.mouseCursor,
    this.overlayColor,
    this.splashRadius,
    this.focusNode,
    this.onFocusChange,
    this.autofocus = false,
    this.applyCupertinoTheme,
    this.tileColor,
    this.title,
    this.subtitle,
    this.isThreeLine = false,
    this.dense,
    this.contentPadding,
    this.secondary,
    this.selected = false,
    this.controlAffinity = ListTileControlAffinity.platform,
    this.shape,
    this.selectedTileColor,
    this.visualDensity,
    this.enableFeedback,
    this.hoverColor,
  }) : _switchListTileType = _SwitchListTileType.adaptive,
       assert(!isThreeLine || subtitle != null),
       assert(activeThumbImage != null || onActiveThumbImageError == null),
       assert(inactiveThumbImage != null || onInactiveThumbImageError == null);

  /// 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:
  ///
  /// {@tool snippet}
  /// ```dart
  /// SwitchListTile(
  ///   value: _isSelected,
  ///   onChanged: (bool newValue) {
  ///     setState(() {
  ///       _isSelected = newValue;
  ///     });
  ///   },
  ///   title: const Text('Selection'),
  /// )
  /// ```
  /// {@end-tool}
  final ValueChanged<bool>? onChanged;

  /// {@macro flutter.material.switch.activeColor}
  ///
  /// Defaults to [ColorScheme.secondary] of the current [Theme].
  final Color? activeColor;

  /// {@macro flutter.material.switch.activeTrackColor}
  ///
  /// Defaults to [ThemeData.toggleableActiveColor] with the opacity set at 50%.
  ///
  /// Ignored if created with [SwitchListTile.adaptive].
  final Color? activeTrackColor;

  /// {@macro flutter.material.switch.inactiveThumbColor}
  ///
  /// Defaults to the colors described in the Material design specification.
  ///
  /// Ignored if created with [SwitchListTile.adaptive].
  final Color? inactiveThumbColor;

  /// {@macro flutter.material.switch.inactiveTrackColor}
  ///
  /// Defaults to the colors described in the Material design specification.
  ///
  /// Ignored if created with [SwitchListTile.adaptive].
  final Color? inactiveTrackColor;

  /// {@macro flutter.material.switch.activeThumbImage}
  final ImageProvider? activeThumbImage;

  /// {@macro flutter.material.switch.onActiveThumbImageError}
  final ImageErrorListener? onActiveThumbImageError;

  /// {@macro flutter.material.switch.inactiveThumbImage}
  ///
  /// Ignored if created with [SwitchListTile.adaptive].
  final ImageProvider? inactiveThumbImage;

  /// {@macro flutter.material.switch.onInactiveThumbImageError}
  final ImageErrorListener? onInactiveThumbImageError;

  /// The color of this switch's thumb.
  ///
  /// Resolved in the following states:
  ///  * [MaterialState.selected].
  ///  * [MaterialState.hovered].
  ///  * [MaterialState.disabled].
  ///
  /// If null, then the value of [activeColor] is used in the selected state
  /// and [inactiveThumbColor] in the default state. If that is also null, then
  /// the value of [SwitchThemeData.thumbColor] is used. If that is also null,
  /// The default value is used.
  final MaterialStateProperty<Color?>? thumbColor;

  /// The color of this switch's track.
  ///
  /// Resolved in the following states:
  ///  * [MaterialState.selected].
  ///  * [MaterialState.hovered].
  ///  * [MaterialState.disabled].
  ///
  /// If null, then the value of [activeTrackColor] is used in the selected
  /// state and [inactiveTrackColor] in the default state. If that is also null,
  /// then the value of [SwitchThemeData.trackColor] is used. If that is also
  /// null, then the default value is used.
  final MaterialStateProperty<Color?>? trackColor;

  /// {@macro flutter.material.switch.trackOutlineColor}
  ///
  /// The [ListTile] will be focused when this [SwitchListTile] requests focus,
  /// so the focused outline color of the switch will be ignored.
  ///
  /// In Material 3, the outline color defaults to transparent in the selected
  /// state and [ColorScheme.outline] in the unselected state. In Material 2,
  /// the [Switch] track has no outline.
  final MaterialStateProperty<Color?>? trackOutlineColor;

  /// The icon to use on the thumb of this switch
  ///
  /// Resolved in the following states:
  ///  * [MaterialState.selected].
  ///  * [MaterialState.hovered].
  ///  * [MaterialState.disabled].
  ///
  /// If null, then the value of [SwitchThemeData.thumbIcon] is used. If this is
  /// also null, then the [Switch] does not have any icons on the thumb.
  final MaterialStateProperty<Icon?>? thumbIcon;

  /// {@macro flutter.material.switch.materialTapTargetSize}
  ///
  /// defaults to [MaterialTapTargetSize.shrinkWrap].
  final MaterialTapTargetSize? materialTapTargetSize;

  /// {@macro flutter.cupertino.CupertinoSwitch.dragStartBehavior}
  final DragStartBehavior dragStartBehavior;

  /// The cursor for a mouse pointer when it enters or is hovering over the
  /// widget.
  ///
  /// If [mouseCursor] is a [MaterialStateProperty<MouseCursor>],
  /// [MaterialStateProperty.resolve] is used for the following [MaterialState]s:
  ///
  ///  * [MaterialState.selected].
  ///  * [MaterialState.hovered].
  ///  * [MaterialState.disabled].
  ///
  /// If null, then the value of [SwitchThemeData.mouseCursor] is used. If that
  /// is also null, then [MaterialStateMouseCursor.clickable] is used.
  final MouseCursor? mouseCursor;

  /// The color for the switch's [Material].
  ///
  /// Resolves in the following states:
  ///  * [MaterialState.pressed].
  ///  * [MaterialState.selected].
  ///  * [MaterialState.hovered].
  ///
  /// If null, then the value of [activeColor] with alpha [kRadialReactionAlpha]
  /// and [hoverColor] is used in the pressed and hovered state. If that is also
  /// null, the value of [SwitchThemeData.overlayColor] is used. If that is
  /// also null, then the default value is used in the pressed and hovered state.
  final MaterialStateProperty<Color?>? overlayColor;

  /// {@macro flutter.material.switch.splashRadius}
  ///
  /// If null, then the value of [SwitchThemeData.splashRadius] is used. If that
  /// is also null, then [kRadialReactionRadius] is used.
  final double? splashRadius;

  /// {@macro flutter.widgets.Focus.focusNode}
  final FocusNode? focusNode;

  /// {@macro flutter.material.inkwell.onFocusChange}
  final ValueChanged<bool>? onFocusChange;

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

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

  /// 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 [ListTileThemeData.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;

  /// 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.ListTile.shape}
  final ShapeBorder? shape;

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

  /// Defines how compact the list tile's layout will be.
  ///
  /// {@macro flutter.material.themedata.visualDensity}
  final VisualDensity? visualDensity;

  /// {@macro flutter.material.ListTile.enableFeedback}
  ///
  /// See also:
  ///
  ///  * [Feedback] for providing platform-specific feedback to certain actions.
  final bool? enableFeedback;

  /// The color for the tile's [Material] when a pointer is hovering over it.
  final Color? hoverColor;

  /// {@macro flutter.cupertino.CupertinoSwitch.applyTheme}
  final bool? applyCupertinoTheme;

  @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 ?? MaterialTapTargetSize.shrinkWrap,
          activeTrackColor: activeTrackColor,
          inactiveTrackColor: inactiveTrackColor,
          inactiveThumbColor: inactiveThumbColor,
          autofocus: autofocus,
          onFocusChange: onFocusChange,
          onActiveThumbImageError: onActiveThumbImageError,
          onInactiveThumbImageError: onInactiveThumbImageError,
          thumbColor: thumbColor,
          trackColor: trackColor,
          trackOutlineColor: trackOutlineColor,
          thumbIcon: thumbIcon,
          applyCupertinoTheme: applyCupertinoTheme,
          dragStartBehavior: dragStartBehavior,
          mouseCursor: mouseCursor,
          splashRadius: splashRadius,
          overlayColor: overlayColor,
        );

      case _SwitchListTileType.material:
        control = Switch(
          value: value,
          onChanged: onChanged,
          activeColor: activeColor,
          activeThumbImage: activeThumbImage,
          inactiveThumbImage: inactiveThumbImage,
          materialTapTargetSize: materialTapTargetSize ?? MaterialTapTargetSize.shrinkWrap,
          activeTrackColor: activeTrackColor,
          inactiveTrackColor: inactiveTrackColor,
          inactiveThumbColor: inactiveThumbColor,
          autofocus: autofocus,
          onFocusChange: onFocusChange,
          onActiveThumbImageError: onActiveThumbImageError,
          onInactiveThumbImageError: onInactiveThumbImageError,
          thumbColor: thumbColor,
          trackColor: trackColor,
          trackOutlineColor: trackOutlineColor,
          thumbIcon: thumbIcon,
          dragStartBehavior: dragStartBehavior,
          mouseCursor: mouseCursor,
          splashRadius: splashRadius,
          overlayColor: overlayColor,
        );
    }

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

    final ThemeData theme = Theme.of(context);
    final SwitchThemeData switchTheme = SwitchTheme.of(context);
    final Set<MaterialState> states = <MaterialState>{
      if (selected) MaterialState.selected,
    };
    final Color effectiveActiveColor = activeColor
      ?? switchTheme.thumbColor?.resolve(states)
      ?? theme.colorScheme.secondary;
    return MergeSemantics(
      child: ListTile(
        selectedColor: effectiveActiveColor,
        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,
        visualDensity: visualDensity,
        focusNode: focusNode,
        onFocusChange: onFocusChange,
        enableFeedback: enableFeedback,
        hoverColor: hoverColor,
      ),
    );
  }
}