Shapes in Flutter Slider (SfSlider)

27 Jul 202518 minutes to read

This section helps to learn about how to customize the shapes of the slider elements.

Track shape

You can change the size and shape of the track using the trackShape property in the SfSlider.

• getPreferredSize() - Returns the size based on the values passed to it.
• paint() - Used to change the track shape.

NOTE

• You must use the thumbCenter and currentValue parameters of paint override method for customizing slider track.
• You must use the startThumbCenter, endThumbCenter, and currentValues parameters of paint override method for customizing range slider and range selector track.

DART

double _value = 5.0;

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: Center(
        child: SfSliderTheme(
          data: SfSliderThemeData(
            activeTrackHeight: 10,
            inactiveTrackHeight: 10,
          ),
          child: SfSlider(
            min: 0.0,
            max: 10.0,
            value: _value,
            trackShape: _SfTrackShape(),
            onChanged: (dynamic newValue) {
              setState(() {
                _value = newValue;
              });
            },
          ),
        ),
      ),
   );
}

class _SfTrackShape extends SfTrackShape {
  @override
  void paint(PaintingContext context, Offset offset, Offset? thumbCenter,
      Offset? startThumbCenter, Offset? endThumbCenter,
      {required RenderBox parentBox,
      required SfSliderThemeData themeData,
      SfRangeValues? currentValues,
      dynamic currentValue,
      required Animation<double> enableAnimation,
      required Paint? inactivePaint,
      required Paint? activePaint,
      required TextDirection textDirection}) {
    Paint paint = Paint()
      ..color = themeData.activeTrackColor!
      ..style = PaintingStyle.stroke
      ..strokeWidth = 1;
    super.paint(context, offset, thumbCenter, startThumbCenter, endThumbCenter,
        parentBox: parentBox,
        themeData: themeData,
        enableAnimation: enableAnimation,
        inactivePaint: inactivePaint,
        activePaint: paint,
        textDirection: textDirection);
  }
}

Thumb shape

You can change the size and shape of the thumb using the thumbShape property in the SfSlider.

• getPreferredSize() - Returns the size based on the values passed to it.
• paint() - Used to change the thumb shape.

NOTE

• You must use the currentValue parameter of paint override method for customizing slider thumb.
• You must use the currentValues parameter of paint override method for customizing range slider and range selector thumbs.

DART

double _value = 4.0;

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: Center(
        child: SfSliderTheme(
          data: SfSliderThemeData(overlayRadius: 0),
          child: SfSlider(
            min: 2.0,
            max: 10.0,
            value: _value,
            thumbShape: _SfThumbShape(),
            onChanged: (dynamic newValue) {
              setState(() {
                _value = newValue;
              });
            },
          ),
        ),
      ),
   );
}

class _SfThumbShape extends SfThumbShape {
  @override
  void paint(PaintingContext context, Offset center,
      {required RenderBox parentBox,
      required RenderBox? child,
      required SfSliderThemeData themeData,
      SfRangeValues? currentValues,
      dynamic currentValue,
      required Paint? paint,
      required Animation<double> enableAnimation,
      required TextDirection textDirection,
      required SfThumb? thumb}) {
      final Path path = Path();

      path.moveTo(center.dx, center.dy);
      path.lineTo(center.dx + 10, center.dy - 15);
      path.lineTo(center.dx - 10, center.dy - 15);
      path.close();
      context.canvas.drawPath(
          path,
          Paint()
            ..color = themeData.activeTrackColor!
            ..style = PaintingStyle.fill
            ..strokeWidth = 2);
  }
}

Divider shape

You can change the size and shape of the divider using the dividerShape property in the SfSlider.

• getPreferredSize() - Returns the size based on the values passed to it.
• paint() - Used to change the divider shape.

NOTE

• You must use the thumbCenter and currentValue parameters of paint override method for customizing slider divider.
• You must use the startThumbCenter, endThumbCenter, and currentValues parameters of paint override method for customizing range slider and range selector divider.

DART

double _value = 6.0;

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfSlider(
        min: 2.0,
        max: 10.0,
        value: _value,
        interval: 1,
        showDividers: true,
        dividerShape: _DividerShape(),
        onChanged: (dynamic newValue) {
          setState(() {
            _value = newValue;
          });
        },
      ),
   );
}

class _DividerShape extends SfDividerShape {
  @override
  void paint(PaintingContext context, Offset center, Offset? thumbCenter,
      Offset? startThumbCenter, Offset? endThumbCenter,
      {required RenderBox parentBox,
      required SfSliderThemeData themeData,
      SfRangeValues? currentValues,
      dynamic currentValue,
      required Paint? paint,
      required Animation<double> enableAnimation,
      required TextDirection textDirection}) {
    bool isActive;

    switch (textDirection) {
      case TextDirection.ltr:
        isActive = center.dx <= thumbCenter!.dx;
        break;
      case TextDirection.rtl:
        isActive = center.dx >= thumbCenter!.dx;
        break;
    }

    context.canvas.drawRect(
        Rect.fromCenter(center: center, width: 5.0, height: 10.0),
        Paint()
          ..isAntiAlias = true
          ..style = PaintingStyle.fill
          ..color = isActive ? themeData.activeTrackColor! : Colors.white);
  }
}

Major and minor ticks shapes

You can change the size and shape of the major and minor ticks using the tickShape and minorTickShape properties in the SfSlider.

• getPreferredSize() - Returns the size based on the values passed to it.
• paint() - Used to change the ticks shape.

NOTE

• You must use the thumbCenter and currentValue parameters of paint override method for customizing slider ticks.
• You must use the startThumbCenter, endThumbCenter, and currentValues parameters of paint override method for customizing range slider and range selector ticks.

DART

double _value = 5.0;

@override
Widget build(BuildContext context) {
  return Scaffold(
     body: SfSlider(
        min: 0.0,
        max: 10.0,
        value: _value,
        interval: 1,
        showTicks: true,
        minorTicksPerInterval: 3,
        tickShape: _SfTickShape(),
        minorTickShape: _SfMinorTickShape(),
        onChanged: (dynamic newValue) {
          setState(() {
            _value = newValue;
          });
        },
      ),
   );
}

class _SfTickShape extends SfTickShape {
  @override
  void paint(PaintingContext context, Offset offset, Offset? thumbCenter,
      Offset? startThumbCenter, Offset? endThumbCenter,
      {required RenderBox parentBox,
      required SfSliderThemeData themeData,
      SfRangeValues? currentValues,
      dynamic currentValue,
      required Animation<double> enableAnimation,
      required TextDirection textDirection}) {
    final Size tickSize = getPreferredSize(themeData);
    final bool isTickRightOfThumb = offset.dx > thumbCenter!.dx;
    final Color begin = isTickRightOfThumb
        ? themeData.disabledInactiveTickColor
        : themeData.disabledActiveTickColor;
    final Color end = isTickRightOfThumb
        ? themeData.inactiveTickColor
        : themeData.activeTickColor;
    final Paint paint = Paint()
      ..isAntiAlias = true
      ..strokeWidth = tickSize.width
      ..color = ColorTween(begin: begin, end: end).evaluate(enableAnimation)!;

    context.canvas.drawLine(
        Offset(
            offset.dx,
            offset.dy -
                2 -
                math.max(themeData.activeTrackHeight,
                    themeData.inactiveTrackHeight)),
        Offset(
            offset.dx,
            offset.dy -
                2 -
                math.max(themeData.activeTrackHeight,
                    themeData.inactiveTrackHeight) -
                tickSize.height),
        paint);
  }
}

class _SfMinorTickShape extends SfTickShape {
  @override
  void paint(PaintingContext context, Offset offset, Offset? thumbCenter,
      Offset? startThumbCenter, Offset? endThumbCenter,
      {required RenderBox parentBox,
      required SfSliderThemeData themeData,
      SfRangeValues? currentValues,
      dynamic currentValue,
      required Animation<double> enableAnimation,
      required TextDirection textDirection}) {
    final Size minorTickSize = getPreferredSize(themeData);
    final bool isMinorTickRightOfThumb = offset.dx > thumbCenter!.dx;

    final Color begin = isMinorTickRightOfThumb
        ? themeData.disabledInactiveMinorTickColor
        : themeData.disabledActiveMinorTickColor;
    final Color end = isMinorTickRightOfThumb
        ? themeData.inactiveMinorTickColor
        : themeData.activeMinorTickColor;
    final Paint paint = Paint()
      ..isAntiAlias = true
      ..strokeWidth = minorTickSize.width
      ..color = ColorTween(begin: begin, end: end).evaluate(enableAnimation)!;

    context.canvas.drawLine(
        Offset(
            offset.dx,
            offset.dy -
                2 -
                math.max(themeData.activeTrackHeight,
                    themeData.inactiveTrackHeight)),
        Offset(
            offset.dx,
            offset.dy -
                2 -
                math.max(themeData.activeTrackHeight,
                    themeData.inactiveTrackHeight) -
                minorTickSize.height),
        paint);
  }
}