absorb method

  1. @override
void absorb (
  1. ScrollPosition other
)
override

Take any current applicable state from the given ScrollPosition.

This method is called by the constructor if it is given an oldPosition. The other argument might not have the same runtimeType as this object.

This method can be destructive to the other ScrollPosition. The other object must be disposed immediately after this call (in the same call stack, before microtask resolution, by whomever called this object's constructor).

If the old ScrollPosition object is a different runtimeType than this one, the ScrollActivity.resetActivity method is invoked on the newly adopted ScrollActivity.

Overriding

Overrides of this method must call super.absorb after setting any metrics-related or activity-related state, since this method may restart the activity and scroll activities tend to use those metrics when being restarted.

Overrides of this method might need to start an IdleScrollActivity if they are unable to absorb the activity from the other ScrollPosition.

Overrides of this method might also need to update the delegates of absorbed scroll activities if they use themselves as a ScrollActivityDelegate.

Implementation

@override
void absorb(ScrollPosition other) {
  super.absorb(other);
  if (other is! ScrollPositionWithSingleContext) {
    goIdle();
    return;
  }
  activity.updateDelegate(this);
  final ScrollPositionWithSingleContext typedOther = other as ScrollPositionWithSingleContext;
  _userScrollDirection = typedOther._userScrollDirection;
  assert(_currentDrag == null);
  if (typedOther._currentDrag != null) {
    _currentDrag = typedOther._currentDrag;
    _currentDrag.updateDelegate(this);
    typedOther._currentDrag = null;
  }
}