apply method
Apply the given progress
level to the effect's target.
Here progress
is a variable that is typically in the range from 0 to 1,
with 0 being the initial state, and 1 the final state of the effect. See
EffectController for details.
This is a main method that MUST be implemented in every derived class.
Implementation
@override
void apply(double progress) {
final dProgress = progress - previousProgress;
target.anchor = Anchor(
target.anchor.x + _offset.x * dProgress,
target.anchor.y + _offset.y * dProgress,
);
}