How to change CupertinoSwitch inactive state color in Flutter

Issue

my question is, how I can change inactive color of CupertinoSwitch in Flutter, with normal Switch it’s fairly easy, because we have property for that, but on CupertinoSwitch (iOS) we do not have these properties.

EDIT:

Here is custom class for now, to achieve that.

import 'dart:ui';

import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/gestures.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/services.dart';

class MyCupertinoSwitch extends StatefulWidget {
  /// Creates an iOS-style switch.
  ///
  /// The [value] parameter must not be null.
  /// The [dragStartBehavior] parameter defaults to [DragStartBehavior.start] and must not be null.
  const MyCupertinoSwitch({
    Key key,
    @required this.value,
    @required this.onChanged,
    this.activeColor,
    this.trackColor,
    this.dragStartBehavior = DragStartBehavior.start,
  })  : assert(value != null),
        assert(dragStartBehavior != null),
        super(key: key);

  /// Whether this switch is on or off.
  ///
  /// Must not be null.
  final bool value;

  /// Called when the user toggles with 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 with the new
  /// value.
  ///
  /// If null, the switch will be displayed as disabled, which has a reduced opacity.
  ///
  /// 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
  /// CupertinoSwitch(
  ///   value: _giveVerse,
  ///   onChanged: (bool newValue) {
  ///     setState(() {
  ///       _giveVerse = newValue;
  ///     });
  ///   },
  /// )
  /// ```
  final ValueChanged<bool> onChanged;

  /// The color to use when this switch is on.
  ///
  /// Defaults to [CupertinoColors.activeGreen] when null and ignores the
  /// [CupertinoTheme] in accordance to native iOS behavior.
  final Color activeColor;

  /// The color to use when this switch is off.
  ///
  /// Defaults to [CupertinoColors.lightBackgroundGray] when null and ignores the
  /// [CupertinoTheme] in accordance to native iOS behavior.
  final Color trackColor;

  /// {@template flutter.cupertino.switch.dragStartBehavior}
  /// Determines the way that drag start behavior is handled.
  ///
  /// If set to [DragStartBehavior.start], the drag behavior used to move the
  /// switch from on to off will begin upon the detection of a drag gesture. If
  /// set to [DragStartBehavior.down] it will begin when a down event is first
  /// detected.
  ///
  /// In general, setting this to [DragStartBehavior.start] will make drag
  /// animation smoother and setting it to [DragStartBehavior.down] will make
  /// drag behavior feel slightly more reactive.
  ///
  /// By default, the drag start behavior is [DragStartBehavior.start].
  ///
  /// See also:
  ///
  ///  * [DragGestureRecognizer.dragStartBehavior], which gives an example for
  ///    the different behaviors.
  ///
  /// {@endtemplate}
  final DragStartBehavior dragStartBehavior;

  @override
  _MyCupertinoSwitchState createState() => _MyCupertinoSwitchState();

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    super.debugFillProperties(properties);
    properties.add(FlagProperty('value',
        value: value, ifTrue: 'on', ifFalse: 'off', showName: true));
    properties.add(ObjectFlagProperty<ValueChanged<bool>>(
        'onChanged', onChanged,
        ifNull: 'disabled'));
  }
}

class _MyCupertinoSwitchState extends State<MyCupertinoSwitch>
    with TickerProviderStateMixin {
  @override
  Widget build(BuildContext context) {
    return Opacity(
      opacity:
          widget.onChanged == null ? _kCupertinoSwitchDisabledOpacity : 1.0,
      child: _CupertinoSwitchRenderObjectWidget(
        value: widget.value,
        activeColor: widget.activeColor ?? CupertinoColors.activeGreen,
        trackColor: widget.trackColor ?? CupertinoColors.lightBackgroundGray,
        onChanged: widget.onChanged,
        vsync: this,
        dragStartBehavior: widget.dragStartBehavior,
      ),
    );
  }
}

class _CupertinoSwitchRenderObjectWidget extends LeafRenderObjectWidget {
  const _CupertinoSwitchRenderObjectWidget({
    Key key,
    this.value,
    this.activeColor,
    this.trackColor,
    this.onChanged,
    this.vsync,
    this.dragStartBehavior = DragStartBehavior.start,
  }) : super(key: key);

  final bool value;
  final Color activeColor;
  final Color trackColor;
  final ValueChanged<bool> onChanged;
  final TickerProvider vsync;
  final DragStartBehavior dragStartBehavior;

  @override
  _RenderCupertinoSwitch createRenderObject(BuildContext context) {
    return _RenderCupertinoSwitch(
      value: value,
      activeColor: activeColor,
      trackColor: trackColor,
      onChanged: onChanged,
      textDirection: Directionality.of(context),
      vsync: vsync,
      dragStartBehavior: dragStartBehavior,
    );
  }

  @override
  void updateRenderObject(
      BuildContext context, _RenderCupertinoSwitch renderObject) {
    renderObject
      ..value = value
      ..activeColor = activeColor
      ..trackColor = trackColor
      ..onChanged = onChanged
      ..textDirection = Directionality.of(context)
      ..vsync = vsync
      ..dragStartBehavior = dragStartBehavior;
  }
}

const double _kTrackWidth = 51.0;
const double _kTrackHeight = 31.0;
const double _kTrackRadius = _kTrackHeight / 2.0;
const double _kTrackInnerStart = _kTrackHeight / 2.0;
const double _kTrackInnerEnd = _kTrackWidth - _kTrackInnerStart;
const double _kTrackInnerLength = _kTrackInnerEnd - _kTrackInnerStart;
const double _kSwitchWidth = 59.0;
const double _kSwitchHeight = 39.0;
// Opacity of a disabled switch, as eye-balled from iOS Simulator on Mac.
const double _kCupertinoSwitchDisabledOpacity = 0.5;

const Duration _kReactionDuration = Duration(milliseconds: 300);
const Duration _kToggleDuration = Duration(milliseconds: 200);

class _RenderCupertinoSwitch extends RenderConstrainedBox {
  _RenderCupertinoSwitch({
    @required bool value,
    @required Color activeColor,
    @required Color trackColor,
    ValueChanged<bool> onChanged,
    @required TextDirection textDirection,
    @required TickerProvider vsync,
    DragStartBehavior dragStartBehavior = DragStartBehavior.start,
  })  : assert(value != null),
        assert(activeColor != null),
        assert(vsync != null),
        _value = value,
        _activeColor = activeColor,
        _trackColor = trackColor,
        _onChanged = onChanged,
        _textDirection = textDirection,
        _vsync = vsync,
        super(
            additionalConstraints: const BoxConstraints.tightFor(
                width: _kSwitchWidth, height: _kSwitchHeight)) {
    _tap = TapGestureRecognizer()
      ..onTapDown = _handleTapDown
      ..onTap = _handleTap
      ..onTapUp = _handleTapUp
      ..onTapCancel = _handleTapCancel;
    _drag = HorizontalDragGestureRecognizer()
      ..onStart = _handleDragStart
      ..onUpdate = _handleDragUpdate
      ..onEnd = _handleDragEnd
      ..dragStartBehavior = dragStartBehavior;
    _positionController = AnimationController(
      duration: _kToggleDuration,
      value: value ? 1.0 : 0.0,
      vsync: vsync,
    );
    _position = CurvedAnimation(
      parent: _positionController,
      curve: Curves.linear,
    )
      ..addListener(markNeedsPaint)
      ..addStatusListener(_handlePositionStateChanged);
    _reactionController = AnimationController(
      duration: _kReactionDuration,
      vsync: vsync,
    );
    _reaction = CurvedAnimation(
      parent: _reactionController,
      curve: Curves.ease,
    )..addListener(markNeedsPaint);
  }

  AnimationController _positionController;
  CurvedAnimation _position;

  AnimationController _reactionController;
  Animation<double> _reaction;

  bool get value => _value;
  bool _value;

  set value(bool value) {
    assert(value != null);
    if (value == _value) return;
    _value = value;
    markNeedsSemanticsUpdate();
    _position
      ..curve = Curves.ease
      ..reverseCurve = Curves.ease.flipped;
    if (value)
      _positionController.forward();
    else
      _positionController.reverse();
  }

  TickerProvider get vsync => _vsync;
  TickerProvider _vsync;

  set vsync(TickerProvider value) {
    assert(value != null);
    if (value == _vsync) return;
    _vsync = value;
    _positionController.resync(vsync);
    _reactionController.resync(vsync);
  }

  Color get activeColor => _activeColor;

  Color get trackColor => _trackColor;
  Color _activeColor;
  Color _trackColor;

  set activeColor(Color value) {
    assert(value != null);
    if (value == _activeColor) return;
    _activeColor = value;
    markNeedsPaint();
  }

  set trackColor(Color value) {
    assert(value != null);
    if (value == _trackColor) return;
    _trackColor = value;
    markNeedsPaint();
  }

  ValueChanged<bool> get onChanged => _onChanged;
  ValueChanged<bool> _onChanged;

  set onChanged(ValueChanged<bool> value) {
    if (value == _onChanged) return;
    final bool wasInteractive = isInteractive;
    _onChanged = value;
    if (wasInteractive != isInteractive) {
      markNeedsPaint();
      markNeedsSemanticsUpdate();
    }
  }

  TextDirection get textDirection => _textDirection;
  TextDirection _textDirection;

  set textDirection(TextDirection value) {
    assert(value != null);
    if (_textDirection == value) return;
    _textDirection = value;
    markNeedsPaint();
  }

  DragStartBehavior get dragStartBehavior => _drag.dragStartBehavior;

  set dragStartBehavior(DragStartBehavior value) {
    assert(value != null);
    if (_drag.dragStartBehavior == value) return;
    _drag.dragStartBehavior = value;
  }

  bool get isInteractive => onChanged != null;

  TapGestureRecognizer _tap;
  HorizontalDragGestureRecognizer _drag;

  @override
  void attach(PipelineOwner owner) {
    super.attach(owner);
    if (value)
      _positionController.forward();
    else
      _positionController.reverse();
    if (isInteractive) {
      switch (_reactionController.status) {
        case AnimationStatus.forward:
          _reactionController.forward();
          break;
        case AnimationStatus.reverse:
          _reactionController.reverse();
          break;
        case AnimationStatus.dismissed:
        case AnimationStatus.completed:
          // nothing to do
          break;
      }
    }
  }

  @override
  void detach() {
    _positionController.stop();
    _reactionController.stop();
    super.detach();
  }

  void _handlePositionStateChanged(AnimationStatus status) {
    if (isInteractive) {
      if (status == AnimationStatus.completed && !_value)
        onChanged(true);
      else if (status == AnimationStatus.dismissed && _value) onChanged(false);
    }
  }

  void _handleTapDown(TapDownDetails details) {
    if (isInteractive) _reactionController.forward();
  }

  void _handleTap() {
    if (isInteractive) {
      onChanged(!_value);
      _emitVibration();
    }
  }

  void _handleTapUp(TapUpDetails details) {
    if (isInteractive) _reactionController.reverse();
  }

  void _handleTapCancel() {
    if (isInteractive) _reactionController.reverse();
  }

  void _handleDragStart(DragStartDetails details) {
    if (isInteractive) {
      _reactionController.forward();
      _emitVibration();
    }
  }

  void _handleDragUpdate(DragUpdateDetails details) {
    if (isInteractive) {
      _position
        ..curve = null
        ..reverseCurve = null;
      final double delta = details.primaryDelta / _kTrackInnerLength;
      switch (textDirection) {
        case TextDirection.rtl:
          _positionController.value -= delta;
          break;
        case TextDirection.ltr:
          _positionController.value += delta;
          break;
      }
    }
  }

  void _handleDragEnd(DragEndDetails details) {
    if (_position.value >= 0.5)
      _positionController.forward();
    else
      _positionController.reverse();
    _reactionController.reverse();
  }

  void _emitVibration() {
    switch (defaultTargetPlatform) {
      case TargetPlatform.iOS:
        HapticFeedback.lightImpact();
        break;
      case TargetPlatform.fuchsia:
      case TargetPlatform.android:
        break;
    }
  }

  @override
  bool hitTestSelf(Offset position) => true;

  @override
  void handleEvent(PointerEvent event, BoxHitTestEntry entry) {
    assert(debugHandleEvent(event, entry));
    if (event is PointerDownEvent && isInteractive) {
      _drag.addPointer(event);
      _tap.addPointer(event);
    }
  }

  @override
  void describeSemanticsConfiguration(SemanticsConfiguration config) {
    super.describeSemanticsConfiguration(config);

    if (isInteractive) config.onTap = _handleTap;

    config.isEnabled = isInteractive;
    config.isToggled = _value;
  }

  final CupertinoThumbPainter _thumbPainter = CupertinoThumbPainter();

  @override
  void paint(PaintingContext context, Offset offset) {
    final Canvas canvas = context.canvas;

    final double currentValue = _position.value;
    final double currentReactionValue = _reaction.value;

    double visualPosition;
    switch (textDirection) {
      case TextDirection.rtl:
        visualPosition = 1.0 - currentValue;
        break;
      case TextDirection.ltr:
        visualPosition = currentValue;
        break;
    }

    final Paint paint = Paint()
      ..color = Color.lerp(trackColor, activeColor, currentValue);

    final Rect trackRect = Rect.fromLTWH(
      offset.dx + (size.width - _kTrackWidth) / 2.0,
      offset.dy + (size.height - _kTrackHeight) / 2.0,
      _kTrackWidth,
      _kTrackHeight,
    );
    final RRect trackRRect = RRect.fromRectAndRadius(
        trackRect, const Radius.circular(_kTrackRadius));
    canvas.drawRRect(trackRRect, paint);

    final double currentThumbExtension =
        CupertinoThumbPainter.extension * currentReactionValue;
    final double thumbLeft = lerpDouble(
      trackRect.left + _kTrackInnerStart - CupertinoThumbPainter.radius,
      trackRect.left +
          _kTrackInnerEnd -
          CupertinoThumbPainter.radius -
          currentThumbExtension,
      visualPosition,
    );
    final double thumbRight = lerpDouble(
      trackRect.left +
          _kTrackInnerStart +
          CupertinoThumbPainter.radius +
          currentThumbExtension,
      trackRect.left + _kTrackInnerEnd + CupertinoThumbPainter.radius,
      visualPosition,
    );
    final double thumbCenterY = offset.dy + size.height / 2.0;
    final Rect thumbBounds = Rect.fromLTRB(
      thumbLeft,
      thumbCenterY - CupertinoThumbPainter.radius,
      thumbRight,
      thumbCenterY + CupertinoThumbPainter.radius,
    );

    context
        .pushClipRRect(needsCompositing, Offset.zero, thumbBounds, trackRRect,
            (PaintingContext innerContext, Offset offset) {
      _thumbPainter.paint(innerContext.canvas, thumbBounds);
    });
  }

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder description) {
    super.debugFillProperties(description);
    description.add(FlagProperty('value',
        value: value, ifTrue: 'checked', ifFalse: 'unchecked', showName: true));
    description.add(FlagProperty('isInteractive',
        value: isInteractive,
        ifTrue: 'enabled',
        ifFalse: 'disabled',
        showName: true,
        defaultValue: true));
  }
}

Let’s see the response from flutter dev team on issue raised below.

Solution

EDIT: support has been added to the flutter’s codebase:

see https://github.com/flutter/flutter/pull/45074/files


you can’t, unfortunately. it is hard coded in switch.dart

you can do some hacky stuff with ShaderMask :


  bool value = false;

  @override
  Widget build(BuildContext context) {
    final Color activeColor = Color.fromARGB(255, 52, 199, 89);

    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
          child: Theme(
        data: ThemeData(),
        child: ShaderMask(
          child: CupertinoSwitch(
            activeColor: activeColor,
            value: value,
            onChanged: (v) => setState(() => value = v),
          ),
          shaderCallback: (r) {
            return LinearGradient(
              colors: value
                  ? [activeColor, activeColor]
                  : [Colors.red, Colors.red],
            ).createShader(r);
          },
        ),
      )),
    );
  }

or use this custom class ( i added a trackColor which is the inactive color ):


import 'dart:ui' show lerpDouble;

import 'package:flutter/cupertino.dart';
import 'package:flutter/foundation.dart';
import 'package:flutter/gestures.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/widgets.dart';
import 'package:flutter/services.dart';

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

/// An iOS-style switch.
///
/// Used to toggle the on/off state of a single setting.
///
/// The switch 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 with a new [value] to update the visual appearance of the switch.
///
/// {@tool sample}
///
/// This sample shows how to use a [CupertinoSwitch] in a [ListTile]. The
/// [MergeSemantics] is used to turn the entire [ListTile] into a single item
/// for accessibility tools.
///
/// ```dart
/// MergeSemantics(
///   child: ListTile(
///     title: Text('Lights'),
///     trailing: CupertinoSwitch(
///       value: _lights,
///       onChanged: (bool value) { setState(() { _lights = value; }); },
///     ),
///     onTap: () { setState(() { _lights = !_lights; }); },
///   ),
/// )
/// ```
/// {@end-tool}
///
/// See also:
///
///  * [Switch], the material design equivalent.
///  * <https://developer.apple.com/ios/human-interface-guidelines/controls/switches/>
class CupertinoSwitch extends StatefulWidget {
  /// Creates an iOS-style switch.
  ///
  /// The [value] parameter must not be null.
  /// The [dragStartBehavior] parameter defaults to [DragStartBehavior.start] and must not be null.
  const CupertinoSwitch({
    Key key,
    @required this.value,
    @required this.onChanged,
    this.activeColor,
    this.trackColor,
    this.dragStartBehavior = DragStartBehavior.start,
  }) : assert(value != null),
        assert(dragStartBehavior != null),
        super(key: key);

  /// Whether this switch is on or off.
  ///
  /// Must not be null.
  final bool value;

  /// Called when the user toggles with 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 with the new
  /// value.
  ///
  /// If null, the switch will be displayed as disabled, which has a reduced opacity.
  ///
  /// 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
  /// CupertinoSwitch(
  ///   value: _giveVerse,
  ///   onChanged: (bool newValue) {
  ///     setState(() {
  ///       _giveVerse = newValue;
  ///     });
  ///   },
  /// )
  /// ```
  final ValueChanged<bool> onChanged;

  /// The color to use when this switch is on.
  ///
  /// Defaults to [CupertinoColors.systemGreen] when null and ignores
  /// the [CupertinoTheme] in accordance to native iOS behavior.
  final Color activeColor;

  final Color trackColor;

  /// {@template flutter.cupertino.switch.dragStartBehavior}
  /// Determines the way that drag start behavior is handled.
  ///
  /// If set to [DragStartBehavior.start], the drag behavior used to move the
  /// switch from on to off will begin upon the detection of a drag gesture. If
  /// set to [DragStartBehavior.down] it will begin when a down event is first
  /// detected.
  ///
  /// In general, setting this to [DragStartBehavior.start] will make drag
  /// animation smoother and setting it to [DragStartBehavior.down] will make
  /// drag behavior feel slightly more reactive.
  ///
  /// By default, the drag start behavior is [DragStartBehavior.start].
  ///
  /// See also:
  ///
  ///  * [DragGestureRecognizer.dragStartBehavior], which gives an example for
  ///    the different behaviors.
  ///
  /// {@endtemplate}
  final DragStartBehavior dragStartBehavior;

  @override
  _CupertinoSwitchState createState() => _CupertinoSwitchState();

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder properties) {
    super.debugFillProperties(properties);
    properties.add(FlagProperty('value', value: value, ifTrue: 'on', ifFalse: 'off', showName: true));
    properties.add(ObjectFlagProperty<ValueChanged<bool>>('onChanged', onChanged, ifNull: 'disabled'));
  }
}

class _CupertinoSwitchState extends State<CupertinoSwitch> with TickerProviderStateMixin {
  @override
  Widget build(BuildContext context) {
    return Opacity(
      opacity: widget.onChanged == null ? _kCupertinoSwitchDisabledOpacity : 1.0,
      child: _CupertinoSwitchRenderObjectWidget(
        value: widget.value,
        activeColor: CupertinoDynamicColor.resolve(
          widget.activeColor ?? CupertinoColors.systemGreen,
          context,
        ),
        trackColor: widget.trackColor,
        onChanged: widget.onChanged,
        vsync: this,
        dragStartBehavior: widget.dragStartBehavior,
      ),
    );
  }
}

class _CupertinoSwitchRenderObjectWidget extends LeafRenderObjectWidget {
  const _CupertinoSwitchRenderObjectWidget({
    Key key,
    this.value,
    this.activeColor,
    this.onChanged,
    this.vsync,
    this.trackColor,
    this.dragStartBehavior = DragStartBehavior.start,
  }) : super(key: key);

  final bool value;
  final Color activeColor;
  final Color trackColor;
  final ValueChanged<bool> onChanged;
  final TickerProvider vsync;
  final DragStartBehavior dragStartBehavior;

  @override
  _RenderCupertinoSwitch createRenderObject(BuildContext context) {
    return _RenderCupertinoSwitch(
      value: value,
      activeColor: activeColor,
      trackColor: trackColor ?? CupertinoDynamicColor.resolve(CupertinoColors.secondarySystemFill, context),
      onChanged: onChanged,
      textDirection: Directionality.of(context),
      vsync: vsync,
      dragStartBehavior: dragStartBehavior,
    );
  }

  @override
  void updateRenderObject(BuildContext context, _RenderCupertinoSwitch renderObject) {
    renderObject
      ..value = value
      ..activeColor = activeColor
      ..trackColor = trackColor ?? CupertinoDynamicColor.resolve(CupertinoColors.secondarySystemFill, context)
      ..onChanged = onChanged
      ..textDirection = Directionality.of(context)
      ..vsync = vsync
      ..dragStartBehavior = dragStartBehavior;
  }
}

const double _kTrackWidth = 51.0;
const double _kTrackHeight = 31.0;
const double _kTrackRadius = _kTrackHeight / 2.0;
const double _kTrackInnerStart = _kTrackHeight / 2.0;
const double _kTrackInnerEnd = _kTrackWidth - _kTrackInnerStart;
const double _kTrackInnerLength = _kTrackInnerEnd - _kTrackInnerStart;
const double _kSwitchWidth = 59.0;
const double _kSwitchHeight = 39.0;
// Opacity of a disabled switch, as eye-balled from iOS Simulator on Mac.
const double _kCupertinoSwitchDisabledOpacity = 0.5;

const Duration _kReactionDuration = Duration(milliseconds: 300);
const Duration _kToggleDuration = Duration(milliseconds: 200);

class _RenderCupertinoSwitch extends RenderConstrainedBox {
  _RenderCupertinoSwitch({
    @required bool value,
    @required Color activeColor,
    @required Color trackColor,
    ValueChanged<bool> onChanged,
    @required TextDirection textDirection,
    @required TickerProvider vsync,
    DragStartBehavior dragStartBehavior = DragStartBehavior.start,
  }) : assert(value != null),
        assert(activeColor != null),
        assert(vsync != null),
        _value = value,
        _activeColor = activeColor,
        _trackColor = trackColor,
        _onChanged = onChanged,
        _textDirection = textDirection,
        _vsync = vsync,
        super(additionalConstraints: const BoxConstraints.tightFor(width: _kSwitchWidth, height: _kSwitchHeight)) {
    _tap = TapGestureRecognizer()
      ..onTapDown = _handleTapDown
      ..onTap = _handleTap
      ..onTapUp = _handleTapUp
      ..onTapCancel = _handleTapCancel;
    _drag = HorizontalDragGestureRecognizer()
      ..onStart = _handleDragStart
      ..onUpdate = _handleDragUpdate
      ..onEnd = _handleDragEnd
      ..dragStartBehavior = dragStartBehavior;
    _positionController = AnimationController(
      duration: _kToggleDuration,
      value: value ? 1.0 : 0.0,
      vsync: vsync,
    );
    _position = CurvedAnimation(
      parent: _positionController,
      curve: Curves.linear,
    )..addListener(markNeedsPaint)
      ..addStatusListener(_handlePositionStateChanged);
    _reactionController = AnimationController(
      duration: _kReactionDuration,
      vsync: vsync,
    );
    _reaction = CurvedAnimation(
      parent: _reactionController,
      curve: Curves.ease,
    )..addListener(markNeedsPaint);
  }

  AnimationController _positionController;
  CurvedAnimation _position;

  AnimationController _reactionController;
  Animation<double> _reaction;

  bool get value => _value;
  bool _value;
  set value(bool value) {
    assert(value != null);
    if (value == _value)
      return;
    _value = value;
    markNeedsSemanticsUpdate();
    _position
      ..curve = Curves.ease
      ..reverseCurve = Curves.ease.flipped;
    if (value)
      _positionController.forward();
    else
      _positionController.reverse();
  }

  TickerProvider get vsync => _vsync;
  TickerProvider _vsync;
  set vsync(TickerProvider value) {
    assert(value != null);
    if (value == _vsync)
      return;
    _vsync = value;
    _positionController.resync(vsync);
    _reactionController.resync(vsync);
  }

  Color get activeColor => _activeColor;
  Color _activeColor;
  set activeColor(Color value) {
    assert(value != null);
    if (value == _activeColor)
      return;
    _activeColor = value;
    markNeedsPaint();
  }

  Color get trackColor => _trackColor;
  Color _trackColor;
  set trackColor(Color value) {
    assert(value != null);
    if (value == _trackColor)
      return;
    _trackColor = value;
    markNeedsPaint();
  }

  ValueChanged<bool> get onChanged => _onChanged;
  ValueChanged<bool> _onChanged;
  set onChanged(ValueChanged<bool> value) {
    if (value == _onChanged)
      return;
    final bool wasInteractive = isInteractive;
    _onChanged = value;
    if (wasInteractive != isInteractive) {
      markNeedsPaint();
      markNeedsSemanticsUpdate();
    }
  }

  TextDirection get textDirection => _textDirection;
  TextDirection _textDirection;
  set textDirection(TextDirection value) {
    assert(value != null);
    if (_textDirection == value)
      return;
    _textDirection = value;
    markNeedsPaint();
  }

  DragStartBehavior get dragStartBehavior => _drag.dragStartBehavior;
  set dragStartBehavior(DragStartBehavior value) {
    assert(value != null);
    if (_drag.dragStartBehavior == value)
      return;
    _drag.dragStartBehavior = value;
  }

  bool get isInteractive => onChanged != null;

  TapGestureRecognizer _tap;
  HorizontalDragGestureRecognizer _drag;

  @override
  void attach(PipelineOwner owner) {
    super.attach(owner);
    if (value)
      _positionController.forward();
    else
      _positionController.reverse();
    if (isInteractive) {
      switch (_reactionController.status) {
        case AnimationStatus.forward:
          _reactionController.forward();
          break;
        case AnimationStatus.reverse:
          _reactionController.reverse();
          break;
        case AnimationStatus.dismissed:
        case AnimationStatus.completed:
        // nothing to do
          break;
      }
    }
  }

  @override
  void detach() {
    _positionController.stop();
    _reactionController.stop();
    super.detach();
  }

  void _handlePositionStateChanged(AnimationStatus status) {
    if (isInteractive) {
      if (status == AnimationStatus.completed && !_value)
        onChanged(true);
      else if (status == AnimationStatus.dismissed && _value)
        onChanged(false);
    }
  }

  void _handleTapDown(TapDownDetails details) {
    if (isInteractive)
      _reactionController.forward();
  }

  void _handleTap() {
    if (isInteractive) {
      onChanged(!_value);
      _emitVibration();
    }
  }

  void _handleTapUp(TapUpDetails details) {
    if (isInteractive)
      _reactionController.reverse();
  }

  void _handleTapCancel() {
    if (isInteractive)
      _reactionController.reverse();
  }

  void _handleDragStart(DragStartDetails details) {
    if (isInteractive) {
      _reactionController.forward();
      _emitVibration();
    }
  }

  void _handleDragUpdate(DragUpdateDetails details) {
    if (isInteractive) {
      _position
        ..curve = null
        ..reverseCurve = null;
      final double delta = details.primaryDelta / _kTrackInnerLength;
      switch (textDirection) {
        case TextDirection.rtl:
          _positionController.value -= delta;
          break;
        case TextDirection.ltr:
          _positionController.value += delta;
          break;
      }
    }
  }

  void _handleDragEnd(DragEndDetails details) {
    if (_position.value >= 0.5)
      _positionController.forward();
    else
      _positionController.reverse();
    _reactionController.reverse();
  }

  void _emitVibration() {
    switch (defaultTargetPlatform) {
      case TargetPlatform.iOS:
        HapticFeedback.lightImpact();
        break;
      case TargetPlatform.fuchsia:
      case TargetPlatform.android:
        break;
    }
  }

  @override
  bool hitTestSelf(Offset position) => true;

  @override
  void handleEvent(PointerEvent event, BoxHitTestEntry entry) {
    assert(debugHandleEvent(event, entry));
    if (event is PointerDownEvent && isInteractive) {
      _drag.addPointer(event);
      _tap.addPointer(event);
    }
  }

  @override
  void describeSemanticsConfiguration(SemanticsConfiguration config) {
    super.describeSemanticsConfiguration(config);

    if (isInteractive)
      config.onTap = _handleTap;

    config.isEnabled = isInteractive;
    config.isToggled = _value;
  }

  @override
  void paint(PaintingContext context, Offset offset) {
    final Canvas canvas = context.canvas;

    final double currentValue = _position.value;
    final double currentReactionValue = _reaction.value;

    double visualPosition;
    switch (textDirection) {
      case TextDirection.rtl:
        visualPosition = 1.0 - currentValue;
        break;
      case TextDirection.ltr:
        visualPosition = currentValue;
        break;
    }

    final Paint paint = Paint()
      ..color = Color.lerp(trackColor, activeColor, currentValue);

    final Rect trackRect = Rect.fromLTWH(
      offset.dx + (size.width - _kTrackWidth) / 2.0,
      offset.dy + (size.height - _kTrackHeight) / 2.0,
      _kTrackWidth,
      _kTrackHeight,
    );
    final RRect trackRRect = RRect.fromRectAndRadius(trackRect, const Radius.circular(_kTrackRadius));
    canvas.drawRRect(trackRRect, paint);

    final double currentThumbExtension = CupertinoThumbPainter.extension * currentReactionValue;
    final double thumbLeft = lerpDouble(
      trackRect.left + _kTrackInnerStart - CupertinoThumbPainter.radius,
      trackRect.left + _kTrackInnerEnd - CupertinoThumbPainter.radius - currentThumbExtension,
      visualPosition,
    );
    final double thumbRight = lerpDouble(
      trackRect.left + _kTrackInnerStart + CupertinoThumbPainter.radius + currentThumbExtension,
      trackRect.left + _kTrackInnerEnd + CupertinoThumbPainter.radius,
      visualPosition,
    );
    final double thumbCenterY = offset.dy + size.height / 2.0;
    final Rect thumbBounds = Rect.fromLTRB(
      thumbLeft,
      thumbCenterY - CupertinoThumbPainter.radius,
      thumbRight,
      thumbCenterY + CupertinoThumbPainter.radius,
    );

    context.pushClipRRect(needsCompositing, Offset.zero, thumbBounds, trackRRect, (PaintingContext innerContext, Offset offset) {
      const CupertinoThumbPainter.switchThumb().paint(innerContext.canvas, thumbBounds);
    });
  }

  @override
  void debugFillProperties(DiagnosticPropertiesBuilder description) {
    super.debugFillProperties(description);
    description.add(FlagProperty('value', value: value, ifTrue: 'checked', ifFalse: 'unchecked', showName: true));
    description.add(FlagProperty('isInteractive', value: isInteractive, ifTrue: 'enabled', ifFalse: 'disabled', showName: true, defaultValue: true));
  }
}

but i don’t recommend neither of them.
I recommend you open an issue in flutter repo https://github.com/flutter/flutter/issues and explain your problem there.

Answered By – Sahandevs

Answer Checked By – Terry (FlutterFixes Volunteer)

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