goBallistic method

@override void goBallistic(double velocity)

Start a physics-driven simulation that settles the pixels position, starting at a particular velocity.

This method defers to ScrollPhysics.createBallisticSimulation, which typically provides a bounce simulation when the current position is out of bounds and a friction simulation when the position is in bounds but has a non-zero velocity.

The velocity should be in logical pixels per second.

Implementation

@override
void goBallistic(double velocity) {
  // A velocity is consumed by nested scroll.
  velocity = velocity - _fling(velocity);

  // Fixed an issue for #3:
  // https://github.com/MTtankkeo/flutter_appbar/issues/3
  if (velocity.abs() == 0 && activity is DragScrollActivity) {
    isNestedScrolling = false;
  }

  // Fixed an issue for #6
  // https://github.com/MTtankkeo/flutter_appbar/issues/6
  if (activity is IdleScrollActivity) {
    isNestedScrolling = false;
  }

  // When infinite scrolling is already possible, there is no need to replace
  // the [BallisticScrollActivity] instance even if the size has changed.
  if (velocity != 0 &&
      isNestedScrolling &&
      activity is BallisticNestedScrollActivity) {
    return;
  }

  assert(hasPixels);
  final Simulation? simulation = physics.createBallisticSimulation(
      // If it's true, must begin non-clamping scrolling.
      isNestedScrolling
          ? copyWith(
              minScrollExtent: -double.infinity,
              maxScrollExtent: double.infinity,
              pixels: totalPixels,
            )
          : copyWith(pixels: totalPixels),
      velocity);

  if (simulation != null) {
    beginActivity(BallisticNestedScrollActivity(
      this,
      simulation,
      context.vsync,
      activity?.shouldIgnorePointer ?? true,
    ));
  } else {
    goIdle();
  }
}