Flutter Dynamic Header.dart

import 'package:flutter/material.dart';

void main() async {
  runApp(DynamicHeader());
}

class DynamicHeader extends StatelessWidget {
  const DynamicHeader({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomePage(),
    );
  }
}

class HomePage extends StatefulWidget {
  const HomePage({
    Key? key,
  }) : super(key: key);

  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  late final ScrollController _controller;
  bool _isScrollAreaCollapsed = false;

  static const HEADER_HEIGHT = 110.0;
  static const Expanded_Color = Color(0xff5379FF);
  static const Collapsed_Color = Color(0xff51C2FE);

  final descText = 'This is another dynamic text text tt  tt t end';
  final descTextStyle = TextStyle(
    color: Colors.white,
    fontSize: 20,
  );
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: CustomScrollView(
        controller: _controller,
        slivers: [
          SliverAppBar(
            backgroundColor:
                _isScrollAreaCollapsed ? Collapsed_Color : Expanded_Color,
            pinned: true,
            title: Column(
              children: [
                Row(
                  mainAxisAlignment: MainAxisAlignment.spaceBetween,
                  children: [
                    Text(
                      _isScrollAreaCollapsed ? 'Wrapped' : 'Hello',
                      style: TextStyle(
                        fontSize: 34,
                        fontWeight: FontWeight.bold,
                      ),
                    ),
                    SizedBox(
                      height: 100,
                      child: IconButton(
                        onPressed: () {},
                        icon: Icon(
                          _isScrollAreaCollapsed
                              ? Icons.expand_less
                              : Icons.expand_more,
                          size: 40,
                        ),
                      ),
                    )
                  ],
                )
              ],
            ),
            collapsedHeight: 60,
            expandedHeight: descTextHeight,
            bottom: HeaderBottom(),
            flexibleSpace: FlexibleSpaceBar(
              background: Padding(
                padding: const EdgeInsets.symmetric(horizontal: 16.0),
                child: Column(
                  children: [
                    Container(
                      height: HEADER_HEIGHT,
                    ),
                    Text(
                      descText,
                      style: descTextStyle,
                    ),
                  ],
                ),
              ),
            ),
          ),
          SliverList(
            delegate: SliverChildListDelegate(
              List.generate(
                20,
                (index) => ListTile(
                  title: Text('Item $index'),
                ),
              ),
            ),
          )
        ],
      ),
    );
  }

  double get descTextHeight {
    const padding = 32;
    final textPainter = TextPainter(
      text: TextSpan(text: descText, style: descTextStyle),
      textScaleFactor: MediaQuery.of(context).textScaleFactor,
      maxLines: 1,
      textDirection: TextDirection.ltr,
    )..layout();
    final width = textPainter.size.width;
    final height = textPainter.size.height;
    final screenWidth = MediaQuery.of(context).size.width;
    final numberofLines = (width / (screenWidth - padding)).ceil();
    return numberofLines * height + HEADER_HEIGHT + 16;
  }

  void _scrollListner() {
    if (_controller.offset > (descTextHeight - 130)) {
      if (_isScrollAreaCollapsed) return;
      setState(() {
        _isScrollAreaCollapsed = true;
      });
    } else {
      if (!_isScrollAreaCollapsed) return;
      setState(() {
        _isScrollAreaCollapsed = false;
      });
    }
  }

  @override
  void initState() {
    super.initState();
    _controller = ScrollController();

    _controller.addListener(_scrollListner);
  }

  @override
  void dispose() {
    _controller.removeListener(_scrollListner);
    _controller.dispose();
    super.dispose();
  }
}

class HeaderBottom extends StatelessWidget implements PreferredSizeWidget {
  HeaderBottom({
    Key? key,
  })  : preferredSize = Size.fromHeight(50.0),
        super(key: key);

  @override
  final Size preferredSize;

  @override
  Widget build(BuildContext context) {
    return Container(
      padding: const EdgeInsets.symmetric(horizontal: 16),
      color: Colors.black.withOpacity(0.2),
      height: 50,
      child: ListView.separated(
        separatorBuilder: (context, index) => const SizedBox(width: 8),
        itemCount: 20,
        scrollDirection: Axis.horizontal,
        itemBuilder: (context, index) {
          return Tab(
            child: Text(
              'Tab ${index + 1}',
              style: TextStyle(
                color:
                    index == 0 ? Colors.white : Colors.white.withOpacity(0.6),
              ),
            ),
          );
        },
      ),
    );
  }
}