CODEWITHSUNDEEP
flutterdartflutter-sliver
ysknsn
ysknsn

Reputation: 99

How to expand SliverAppBar programmatically

I have a SliverAppBar, which scrolls up to shrink and scrolls down to expand.

I want to expand SliverAppBar when I switch BottomNavigationBar.

Under the current situation, the state of SliverAppBar before switching is kept.

This is my code. https://gist.github.com/ysknsn/d90a84a180e32de5b0691de874c65d55

Any advices are helpful. Thanks.

Upvotes: 2

Views: 3170

Answers (2)

LIJU DANIEL
LIJU DANIEL

Reputation: 138

Add a scroll controller to your 'Custom Scroll View'

ScrollController _scrollController;

Widget build(BuildContext context) {
_scrollController = ScrollController();
return Scaffold(
body: CustomScrollView( shrinkWrap: true, controller: _scrollController,
physics: BouncingScrollPhysics(),
slivers: <Widget>[
SliverAppBar(
pinned: false,
:
:
:
:
:
:
:
:
:
onPressed: () {// Scroll to top when on click => Expand 
_scrollController.animateTo(
_scrollController.position.minScrollExtent,
duration:Duration(milliseconds:1300),
curve: Curves.decelerate,);
 },

onPressed: () {// Scroll to bottom when on click => Collapse
scrollController.animateTo(
    scrollController.position.maxScrollExtent,
    duration: Duration(milliseconds: 1300),
    curve: Curves.decelerate,
  );
 },

Upvotes: 2

LgFranco
LgFranco

Reputation: 1044

Just do the same you did to the TabController...

Put it in a local variable:

  TabController _tabController;
  ScrollController _scrollController;

  int _selectedIndex = 0;

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

Then use it in your NestedScrollView`

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: DefaultTabController(

        length: _tabController.length,
        child: NestedScrollView(
          controller: _scrollController,
          key: PageStorageKey(widget.title),
          ...

Then update the position when you click:

  void _onItemTapped(int index) {
    _scrollController.jumpTo(0);
    setState(() {
      _selectedIndex = index;
      _tabController.index = index;
    });
  }

Upvotes: 2

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