1. protected
ExtentScrollBehavior createScrollBehavior()

Use the value returned by ScrollConfiguration.createScrollBehavior. If this widget doesn't have a ScrollConfiguration ancestor, or its createScrollBehavior callback is null, then return a new instance of OverscrollWhenScrollableBehavior.

Source

@protected
ExtentScrollBehavior createScrollBehavior() {
  return ScrollConfiguration.of(context)?.createScrollBehavior();
}