flutter-sport/lib/widgets/persistent_header.dart

import 'package:flutter/material.dart';

class PersistentHeader extends SliverPersistentHeaderDelegate {
  final double max;
  final double min;
  final Widget child;

  PersistentHeader({this.max = 50.0, this.min = 50.0, @required this.child});

  @override
  Widget build(BuildContext context, double shrinkOffset, bool overlapsContent) {
    return child;
  }

  @override
  double get maxExtent => max;

  @override
  double get minExtent => min;

  @override
  bool shouldRebuild(SliverPersistentHeaderDelegate oldDelegate) => oldDelegate != this;
}