gradient_slider 1.3.1

Slider and range slider with gradient tracks, image thumbs, a buffer track and full track styling.

Slider and range slider with gradient tracks, image thumbs, a buffer track and full track styling.

Features

• Works with both Slider and RangeSlider
• Custom thumb image, from an asset or any ImageProvider
• Default Material thumb, or no thumb at all
• Active and inactive track gradients
• Gradient anchored to the track, or compressed into the active portion
• Secondary (buffer) track for download and playback progress
• Track border width and color
• Track corner radius, from fully rounded to square
• Configurable active track height
• Fades correctly when the slider is disabled
• Keeps any inherited SliderTheme settings

Usage

 GradientSlider(
  thumbAsset: 'assets/vert_thumb.png',
  thumbHeight: 30,
  thumbWidth: 30,
  trackBorder: 1,
  trackBorderColor: Colors.black,
  activeTrackGradient: const LinearGradient(colors: [Colors.pink, Colors.blue]),
  inactiveTrackGradient:
      LinearGradient(colors: [Colors.grey.shade300, Colors.grey.shade800]),
  slider: Slider(value: 0.5, onChanged: (value) {}
  ),
)

Thumb modes

Image thumb — pass thumbAsset:

GradientSlider(
  thumbAsset: 'assets/vert_thumb.png',
  thumbHeight: 30,
  thumbWidth: 30,
  slider: Slider(value: 0.5, onChanged: (value) {}),
)

Any ImageProvider works too — network, file, memory, or a package: asset — via thumbImage, which takes precedence over thumbAsset:

GradientSlider(
  thumbImage: const NetworkImage('https://example.com/thumb.png'),
  thumbHeight: 30,
  thumbWidth: 30,
  slider: Slider(value: 0.5, onChanged: (value) {}),
)

Default Material thumb — just omit thumbAsset:

GradientSlider(
  activeTrackGradient: const LinearGradient(colors: [Colors.pink, Colors.blue]),
  slider: Slider(value: 0.5, onChanged: (value) {}),
)

No thumb — set showThumb: false. The track still responds to drags:

GradientSlider(
  showThumb: false,
  activeTrackGradient: const LinearGradient(colors: [Colors.pink, Colors.blue]),
  slider: Slider(value: 0.5, onChanged: (value) {}),
)

thumbHeight and thumbWidth only apply to the image thumb.

Note: a showThumb: false slider is slightly wider than one with a thumb. Flutter derives the track's horizontal padding from the thumb and overlay size, so hiding both collapses that padding to zero. If you stack a no-thumb slider next to normal ones and need them to line up, wrap it in Padding to compensate.

Gradient mapping

By default the gradient is anchored to the whole track, so the filled portion shows only the slice it covers — a thumb near the start reveals just the first colours. Set gradientSpansTrack: false to fit the entire ramp into the active portion instead:

GradientSlider(
  gradientSpansTrack: false,
  activeTrackGradient: const LinearGradient(colors: [Colors.pink, Colors.blue]),
  slider: Slider(value: 0.3, onChanged: (value) {}),
)

This matters most for a RangeSlider, where the span between the thumbs can be narrow: anchored, it shows only a sliver of the gradient; compressed, the full ramp fits between the thumbs wherever they sit.

Track shape

The track is fully rounded by default. trackRadius overrides that — 0 gives square corners, and anything larger than half the track height is clamped:

GradientSlider(
  trackHeight: 20,
  trackRadius: 4,
  activeTrackGradient: const LinearGradient(colors: [Colors.pink, Colors.blue]),
  slider: Slider(value: 0.5, onChanged: (value) {}),
)

Active track height

Material draws a Slider's active side 2px taller than its inactive side, but draws a RangeSlider uniformly. additionalActiveTrackHeight overrides both — set 0 for a flat track, or set it explicitly to make the two widgets match:

GradientSlider(
  trackHeight: 10,
  additionalActiveTrackHeight: 0,
  activeTrackGradient: const LinearGradient(colors: [Colors.pink, Colors.blue]),
  slider: Slider(value: 0.5, onChanged: (value) {}),
)

Secondary (buffer) track

Slider.secondaryTrackValue now renders — the buffer is drawn between the thumb and that value, as in a download or playback progress bar. It uses SliderThemeData.secondaryActiveTrackColor unless you pass secondaryTrackGradient:

GradientSlider(
  activeTrackGradient: const LinearGradient(colors: [Colors.pink, Colors.blue]),
  secondaryTrackGradient:
      const LinearGradient(colors: [Colors.white24, Colors.white38]),
  slider: Slider(
    value: 0.3,
    secondaryTrackValue: 0.7,
    onChanged: (value) {},
  ),
)

As in Material, the buffer only appears when the secondary value is ahead of the thumb. RangeSlider has no secondary track, so this applies to Slider only.

Styling the default thumb

Set the thumb color on the Slider you pass to slider::

GradientSlider(
  slider: Slider(
    value: 0.5,
    thumbColor: Colors.white,
    onChanged: (value) {},
  ),
)

Range slider

Pass a RangeSlider as slider: — same widget, no extra setup. The gradient fills the span between the two thumbs:

GradientSlider(
  trackHeight: 10,
  activeTrackGradient: const LinearGradient(colors: [Colors.pink, Colors.blue]),
  inactiveTrackGradient:
      LinearGradient(colors: [Colors.grey.shade300, Colors.grey.shade800]),
  slider: RangeSlider(
    values: rangeValues,
    min: 0,
    max: 10,
    onChanged: (v) => setState(() => rangeValues = v),
  ),
)

thumbAsset, trackBorder and the disabled fade all work exactly as they do for a single-thumb slider. Use rangeThumbShape for a fully custom thumb, the counterpart of thumbShape.

Two differences worth knowing:

• showThumb: false applies to Slider only. A range slider always keeps its thumbs, since without them there is no cue as to which end you are dragging.
• additionalActiveTrackHeight defaults to 0 here and 2 for a Slider, matching Material. Set it explicitly and both honour it.

Theming

GradientSlider merges onto the inherited SliderTheme rather than replacing it, so anything it doesn't set itself — tick marks, value indicator, overlay color, and so on — can still be configured from a SliderTheme (or ThemeData.sliderTheme) above it:

SliderTheme(
  data: const SliderThemeData(
    activeTickMarkColor: Colors.white,
    showValueIndicator: ShowValueIndicator.always,
  ),
  child: GradientSlider(
    activeTrackGradient: const LinearGradient(colors: [Colors.pink, Colors.blue]),
    slider: Slider(value: 0.5, divisions: 5, label: '50%', onChanged: (value) {}),
  ),
)

Type	Properties
String?	thumbAsset
ImageProvider?	thumbImage
double	thumbHeight
double	thumbWidth
bool	showThumb
SliderComponentShape	thumbShape
RangeSliderThumbShape	rangeThumbShape
SliderComponentShape	overlayShape
Widget	slider
Gradient	activeTrackGradient
Gradient	inactiveTrackGradient
Color	inactiveTrackColor
double	trackHeight
double	trackBorder
Color	trackBorderColor
bool	gradientSpansTrack
double?	trackRadius
double?	additionalActiveTrackHeight
Gradient?	secondaryTrackGradient