Implementing Collapsing Toolbar in Flutter

Question

I am trying to implement collapsing toolbar in my app using SliverApp bar, but the problem is that the SliverAppBar is overlapping my content when the SliverAppBar is collapsed, I am attaching the gif for more understanding,

the content in the green background is going under the toolbar, I want to avoid that, any leads are appreciated.

  @override
  Widget build(BuildContext context) {
    // TODO: implement buildr
    var _tabs = {"1", "2", "3"};
    return Scaffold(
      backgroundColor: Colors.white,
      body: NestedScrollView(
          headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
            return <Widget>[
              SliverOverlapAbsorber(
                  handle:
                      NestedScrollView.sliverOverlapAbsorberHandleFor(context),
                  child: SliverAppBar(
                    expandedHeight: 250.0,
                    floating: false,
                    pinned: true,
                    flexibleSpace: FlexibleSpaceBar(
                        centerTitle: true,
                        background: Container(
                          decoration: BoxDecoration(
                            shape: BoxShape.rectangle,
                            image: DecorationImage(
                              fit: BoxFit.fill,
                              image: CachedNetworkImageProvider(
                                  newsPost.photos[0].url),
                            ),
                          ),
                        )),
                    forceElevated: innerBoxIsScrolled,
                  ))
            ];
          },
          body: SafeArea(
            top: false,
            bottom: false,
            child: Builder(
              builder: (BuildContext context) {
                return CustomScrollView(
                  slivers: <Widget>[
                    SliverOverlapInjector(
                      handle: NestedScrollView.sliverOverlapAbsorberHandleFor(
                          context),
                    ),
                    SliverPadding(
                      padding: const EdgeInsets.all(8.0),
                      sliver: SliverFillRemaining(child: _getBody()),
                    ),
                  ],
                );
              },
            ),
          )),
    );
  }

Ume

What is your goal, to make the text go over the app bar? – Poliomyelitis

Answer 1

SliverAppBar Creates a material design app bar that can be placed in a NestedScrollView. Both combinly help us in achieving parallax scrolling.

SafeArea(
      child: Scaffold(
        body: NestedScrollView(
          headerSliverBuilder: (BuildContext context, bool innerBoxIsScrolled) {
            return <Widget>[
              SliverAppBar(
                expandedHeight: 240.0,
                floating: false,
                pinned: true,
                flexibleSpace: FlexibleSpaceBar(
                    centerTitle: true,
                    title: Text(
                      "App Bar",
                    ),
                    background: Image.network(
                      "https://images.pexels.com/photos/4148020/pexels-photo-4148020.jpeg",
                      fit: BoxFit.cover,
                    )),
              ),
            ];
          },
          body: Center(
            child: Text("Hello World!!!"),
          ),
        ),
      ),
    );

Galop

Answer 2

I think you should use SliverList instead of SliverFillRemaining.

body: SafeArea(
        top: false,
        bottom: false,
        child: Builder(
          builder: (BuildContext context) {
            return CustomScrollView(
              shrinkWrap: true,
              slivers: <Widget>[
                SliverOverlapInjector(
                  handle: NestedScrollView.sliverOverlapAbsorberHandleFor(
                      context),
                ),
                SliverPadding(
                  padding: const EdgeInsets.all(0.0),
                  sliver: SliverList(
                    delegate: SliverChildBuilderDelegate((context, index) {
                      return Text('Lorem ipsum dolor sit');
                    }, childCount: 1),
                  ),
                ),
              ],
            );
          },
        ),
      )

Savior