Breaking News: Grepper is joining You.com. Read the official announcement!

how to show appbar when scrolling in flutter

Lively Louse answered on August 10, 2021 Popularity 9/10 Helpfulness 1/10

answer how to show appbar when scrolling in flutter

related flutter scroll appbar

how to show appbar when scrolling in flutter

Comment

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  // Height of your Container
  static final _containerHeight = 100.0;

  // You don't need to change any of these variables
  var _fromTop = -_containerHeight;
  var _controller = ScrollController();
  var _allowReverse = true, _allowForward = true;
  var _prevOffset = 0.0;
  var _prevForwardOffset = -_containerHeight;
  var _prevReverseOffset = 0.0;

  @override
  void initState() {
    super.initState();
    _controller.addListener(_listener);
  }

  // entire logic is inside this listener for ListView
  void _listener() {
    double offset = _controller.offset;
    var direction = _controller.position.userScrollDirection;

    if (direction == ScrollDirection.reverse) {
      _allowForward = true;
      if (_allowReverse) {
        _allowReverse = false;
        _prevOffset = offset;
        _prevForwardOffset = _fromTop;
      }

      var difference = offset - _prevOffset;
      _fromTop = _prevForwardOffset + difference;
      if (_fromTop > 0) _fromTop = 0;
    } else if (direction == ScrollDirection.forward) {
      _allowReverse = true;
      if (_allowForward) {
        _allowForward = false;
        _prevOffset = offset;
        _prevReverseOffset = _fromTop;
      }

      var difference = offset - _prevOffset;
      _fromTop = _prevReverseOffset + difference;
      if (_fromTop < -_containerHeight) _fromTop = -_containerHeight;
    }
    setState(() {}); // for simplicity I'm calling setState here, you can put bool values to only call setState when there is a genuine change in _fromTop
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("ListView")),
      body: Stack(
        children: <Widget>[
          _yourListView(),
          Positioned(
            top: _fromTop,
            left: 0,
            right: 0,
            child: _yourContainer(),
          )
        ],
      ),
    );
  }

  Widget _yourListView() {
    return ListView.builder(
      itemCount: 100,
      controller: _controller,
      itemBuilder: (_, index) => ListTile(title: Text("Item $index")),
    );
  }

  Widget _yourContainer() {
    return Opacity(
      opacity: 1 - (-_fromTop / _containerHeight),
      child: Container(
        height: _containerHeight,
        color: Colors.red,
        alignment: Alignment.center,
        child: Text("Your Container", style: TextStyle(fontSize: 32, fontWeight: FontWeight.bold, color: Colors.white)),
      ),
    );
  }
}

Popularity 9/10 Helpfulness 1/10 Language dart

Source: stackoverflow.com

Tags: appbar dart flutter show when

Link to this answer
Share Copy Link

Contributed on Dec 04 2021

Lively Louse

0 Answers Avg Quality 2/10

Closely Related Answers

flutter scroll appbar

Comment

class _SomePageState extends State<SomePage> with SingleTickerProviderStateMixin {
  late final TabController _tabController;

  @override
  void initState() {
    super.initState();
    _tabController = TabController(length: 2, vsync: this);
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: NestedScrollView(
        headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
          return <Widget>[
            SliverAppBar(
              title: Text('Weight Tracker'),
              pinned: true,
              floating: true,
              forceElevated: innerBoxIsScrolled,
              bottom: TabBar(
                tabs: <Tab>[
                  Tab(text: 'STATISTICS'),
                  Tab(text: 'HISTORY'),
                ],
                controller: _tabController,
              ),
            ),
          ];
        },
        body: TabBarView(
          controller: _tabController,
          children: <Widget>[
            StatisticsPage(),
            HistoryPage(),
          ],
        ),
      ),
    );
  }
}

Popularity 9/10 Helpfulness 4/10 Language whatever

Source: stackoverflow.com

Tags: appbar ap

Link to this answer
Share Copy Link

Contributed on Aug 10 2021

Faiz

0 Answers Avg Quality 2/10

how to show appbar when scrolling in flutter

Contents

More Related Answers

how to show appbar when scrolling in flutter

Closely Related Answers

flutter scroll appbar

Grepper

Documentation

Social

Legal

Contact

Oops, You will need to install Grepper and log-in to perform this action.