estimatedChildCount property Null safety
override
Returns an estimate of the number of children this delegate will build.
Used to estimate the maximum scroll offset if estimateMaxScrollOffset returns null.
Return null if there are an unbounded number of children or if it would be too difficult to estimate the number of children.
This must return a precise number once build has returned null, as it used to implement RenderSliverBoxChildManager.childCount.
Implementation
@override
int? get estimatedChildCount => childCount;