IndexedWidgetBuilder typedef Null safety
Signature for a function that creates a widget for a given index, e.g., in a list.
Used by ListView.builder and other APIs that use lazily-generated widgets.
- WidgetBuilder, which is similar but only takes a BuildContext.
- TransitionBuilder, which is similar but also takes a child.
- NullableIndexedWidgetBuilder, which is similar but may return null.
typedef IndexedWidgetBuilder = Widget Function(BuildContext context, int index);