diplomatic-quarter/lib/widgets/others/sliver_app_bar_delegate.dart

import 'dart:math';

import 'package:flutter/cupertino.dart';

class SliverAppBarDelegate extends SliverPersistentHeaderDelegate {
  SliverAppBarDelegate({
    @required this.minHeight,
    @required this.maxHeight,
    @required this.child,
  });

  final double minHeight;
  final double maxHeight;
  final Widget child;

  @override
  double get minExtent => minHeight;

  @override
  double get maxExtent => max(maxHeight, minHeight);

  @override
  Widget build(
      BuildContext context,
      double shrinkOffset,
      bool overlapsContent)
  {
    return new SizedBox.expand(child: child);
  }
  @override
  bool shouldRebuild(SliverAppBarDelegate oldDelegate) {
    return false;
  }
}