Flings the timeline with an optional force (defaults to a critically damped spring within lowerBound and upperBound) and initial velocity. If velocity is positive, the animation will complete, otherwise it will dismiss.
Source
Future<Null> fling({ double velocity: 1.0, Force force }) {
force ??= kDefaultSpringForce.copyWith(left: lowerBound, right: upperBound);
_direction = velocity < 0.0 ? _AnimationDirection.reverse : _AnimationDirection.forward;
return animateWith(force.release(value, velocity));
}