Use setState in ListView

Question

I trying to get data from two tables and display to ListView.

 child: Container(
                  child: StreamBuilder<List<ABC>>(
                      stream: _abcBloc
                          .getListStream,
                      builder: (context, snapshot) {
                        switch (snapshot.connectionState) {
                          case ConnectionState.waiting:
                            return Center(
                              child: Image.asset(
                                'assets/loading.gif',
                                width: 200.0,
                                height: 200.0,
                              ),
                            );
                            break;

                          case ConnectionState.active:
                            if (snapshot.data.isEmpty) {
                              return Container(child: Text('empty'));
                            } else {
                              return ListView.builder(
                                  shrinkWrap: true,
                                  itemCount: snapshot.data.length,
                                  itemBuilder: (context, index) {
                                    var _reading = snapshot.data[index];
                                    var name;

                                    _abcBloc.getName(_reading.Id)
                                        .then((onValue) {
                                      name = onValue.name;
                                    });

                                    return InkWell(
                                        onTap: () {},
                                        child: Padding(
                                          padding: EdgeInsets.all(10),
                                          child: Column(
                                            children: <Widget>[
                                              Text(name == null ? '' : name),
                                            ],
                                          ),
                                        ));
                                  });
                            }
                            break;

                          default:
                            return Text("edwqd");
                        }
                      }))

Firstly it will call _abcBloc.getListStream. I was able to get the data in this line (var _reading = snapshot.data[index];).

After that I want to get the name from another table by calling this function _abcBloc.getName(_reading.Id). However, the name is always show empty.

Answer 1

Whenever you are working with Future and creating widget based on value of your future, you should always use FutureBuilder.

Replace your ListView.builder with following code:

ListView.builder(
  shrinkWrap: true,
  itemCount: snapshot.data.length,
  itemBuilder: (context, index) {
  var _reading = snapshot.data[index];
  var name;

  // _abcBloc.getName(_reading.Id)
  //     .then((onValue) {
  //   name = onValue.name;
  // });

  return FutureBuilder(
    future: _abcBloc.getName(_reading.Id),
    builder: (BuildContext context, AsyncSnapshot snapshot) {
      if(!snapshot.hasData) return Container();
      name = snapshot.data;
      return InkWell(
      onTap: () {},
      child: Padding(
        padding: EdgeInsets.all(10),
        child: Column(
          children: <Widget>[
            Text(name == null ? '' : name),
          ],
        ),
      ))
    },
  );
});

Hope this helps, in case of any doubts please comment. If it works for you don't forget to accept and up-vote the answer.