builder property Null safety

NullableIndexedWidgetBuilder builder
final

Called to build children for the sliver.

Will be called only for indices greater than or equal to zero and less than childCount (if childCount is non-null).

Should return null if asked to build a widget with a greater index than exists.

The delegate wraps the children returned by this builder in RepaintBoundary widgets.

Implementation

final NullableIndexedWidgetBuilder builder;