HeroPlaceholderBuilder typedef Null safety
Signature for a function that builds a Hero placeholder widget given a child and a Size.
The child can optionally be part of the returned widget tree. The returned
widget should typically be constrained to
heroSize, if it doesn't do so
- TransitionBuilder, which is similar but only takes a BuildContext and a child widget.
typedef HeroPlaceholderBuilder = Widget Function( BuildContext context, Size heroSize, Widget child, );