Scrollbar.list constructor

Scrollbar.list({ Key? key, required ListController controller, required Widget child, int thickness = 1, Axis scrollDirection = Axis.vertical, CellStyle trackStyle = const CellStyle(dim: true), CellStyle thumbStyle = CellStyle.none, bool showWhenFits = true, })

Scrollbar for a ListView, including partial visibility within oversized items. Unmeasured items count equally, so geometry is approximate for mixed sizes. Dragging to either endpoint reaches the actual content edge.

Implementation

Scrollbar.list({
  super.key,

  /// The controller of the list in [child]; give that list the same
  /// controller. The thumb follows [ListController.scrollFraction] and
  /// [ListController.visibleFraction], and a click or drag on the bar calls
  /// [ListController.jumpToFraction], which scrolls without moving the
  /// list's cursor.
  required ListController controller,
  required this.child,
  this.thickness = 1,
  this.scrollDirection = Axis.vertical,
  this.trackStyle = const CellStyle(dim: true),
  this.thumbStyle = CellStyle.none,
  this.showWhenFits = true,
}) : _metrics = (() {
       // Fixed precision keeps the bar independent of whether the viewport
       // spans many short items or part of one oversized item.
       const units = 1000000;
       final visible = (controller.visibleFraction * units).round();
       return (
         units,
         visible,
         (controller.scrollFraction * (units - visible)).round(),
       );
     }),
     _scrollTo = controller.jumpToFraction;