build method

Widget build (BuildContext context, int index)

Returns the child with the given index.

Should return null if asked to build a widget with a greater index than exists. If this returns null, estimatedChildCount must subsequently return a precise non-null value.

Subclasses typically override this function and wrap their children in AutomaticKeepAlive and RepaintBoundary widgets.

Implementation 

Widget build(BuildContext context, int index);