How to use FutureBuilder inside SliverList

Question

I want to covert ListView to CustomScrollView so I need to convert my FutureBuilder into SliverList.

Here is my code:

class LatestNewsList extends StatefulWidget {
  @override
  _LatestNewsListState createState() => _LatestNewsListState();
}

class _LatestNewsListState extends State<LatestNewsList> {
  @override
  Widget build(BuildContext context) {
    return FutureBuilder<List<Data>>(
      future: getQuake(),
      builder: (context, snapshot){
        if(snapshot.hasError) print(snapshot.error);

        return snapshot.hasData
            ? NewsList(latestNews: snapshot.data,)
            : Center(child: CircularProgressIndicator());
      },
    );
  }
}

class NewsList extends StatelessWidget {
  final List<Data> latestNews;

  NewsList({this.latestNews});

  @override
  Widget build(BuildContext context) {



    return new ListView.builder(
        itemCount: latestNews.length,
        itemBuilder: (context, index){
          return new GestureDetector(
            onTap: () {
              Navigator.push(
                  context,
                  MaterialPageRoute(
                      builder: (context) => Browser(url: latestNews[index].post_link,)
                  )
              );
            },
            child: new LatestNewsItem(
              post_title: latestNews[index].post_title,
              post_link: latestNews[index].post_link,
              img_src: latestNews[index].img_src,
            ),
          );
        }
    );
  }
}

How to convert this same FutureBuilder logic into SliverList?

Answer 1

The children of a CustomScrollView must be slivers, you can not use a FutureBuilder.

Instead, rebuild the CustomScrollView when the future completes:

// build fixed items outside of the FutureBuilder for efficiency
final someOtherSliver = SliverToBoxAdapter(...);

return FutureBuilder<List<Data>>(
  future: getQuake(), // this is a code smell. Make sure that the future is NOT recreated when build is called. Create the future in initState instead.
  builder: (context, snapshot){
    Widget newsListSliver;
    if(snapshot.hasData) {
      newsListSliver = SliverList(delegate: SliverChildBuilderDelegate(...))
    } else {
      newsListSliver = SliverToBoxAdapter(child: CircularProgressIndicator(),);
    }

    return CustomScrollView(
      slivers: <Widget>[
        someOtherSliver,
        newsListSliver
      ],
    );
  },
);

If you have multiple slivers which depend on Futures or Streams, you can chain the builders:

return FutureBuilder<..>(
  ...
  builder: (context, snapshot1) {
    return FutureBuilder<..>(
      ...
      builder: (context, snapshot2) {
        return CustomScrollView(...);
      }
    )
  }
)

Answer 2

Use SliverFillRemaining

Widget build(BuildContext context) {
return new Scaffold(
  body: CustomScrollView(
    slivers: <Widget>[
      SliverFillRemaining(
        child: FutureBuilder(
          future: getData(),
          builder: (context, snapshot) {
            if (snapshot.data == null)
              return new Container(
                child: Center(child: new CircularProgressIndicator()),
              );
            else
              return Text(snapshot.data.name);
          },
        ),
      )
    ],
  )
);

OR use SliverList

Widget build(BuildContext context) {
return new Scaffold(
  body: CustomScrollView(
    slivers: <Widget>[
         SliverList(
        delegate: SliverChildListDelegate([Container(
            child: FutureBuilder(
             future : getData(),
             builder: (C,snap){
                //do whatever you want
              }
          )
          )]),
        )
      ]
    )
  )
 }