TweenVisitor<T extends Object> typedef
Null safety
Signature for callbacks passed to ImplicitlyAnimatedWidgetState.forEachTween.
The tween argument should contain the current tween value. This will
initially be null when the state is first initialized.
The targetValue argument should contain the value toward which the state
is animating. For instance, if the state is animating its widget's
opacity value, then this argument should contain the widget's current
opacity value.
The constructor argument should contain a function that takes a value
(the widget's value being animated) and returns a tween beginning at that
value.
forEachTween() is expected to update its tween value to the return value
of this visitor.
The <T> parameter specifies the type of value that's being animated.
Implementation
typedef TweenVisitor<T extends Object> = Tween<T>? Function(Tween<T>? tween, T targetValue, TweenConstructor<T> constructor);