The relative position of the zero scroll offset.
For example, if anchor is 0.5 and the AxisDirection determined by scrollDirection and reverse is AxisDirection.down or AxisDirection.up, then the zero scroll offset is vertically centered within the viewport. If the anchor is 1.0, and the axis direction is AxisDirection.right, then the zero scroll offset is on the left edge of the viewport.
Most scroll views by default are ordered GrowthDirection.forward. Changing the default values of ScrollView.anchor, ScrollView.center, or both, can configure a scroll view for GrowthDirection.reverse.
This sample shows a CustomScrollView, with Radio buttons in the AppBar.bottom that change the AxisDirection to illustrate different configurations. The CustomScrollView.anchor and CustomScrollView.center properties are also set to have the 0 scroll offset positioned in the middle of the viewport, with GrowthDirection.forward and GrowthDirection.reverse illustrated on either side. The sliver that shares the CustomScrollView.center key is positioned at the CustomScrollView.anchor.link
To create a local project with this code sample, run:
flutter create --sample=scroll_view.ScrollView.anchor.1 mysample
final double anchor;