I'm trying to create a ListView with some data received from Firebase, but I keep getting this message. I have tried with FutureBuilder but nothing was useful

The argument type 'Future' can't be assigned to the parameter type 'Widget?'

Code is here:

class CityScreen extends StatelessWidget {
  const CityScreen({Key? key}) : super(key: key);

  Future<ListView> CreateList() async {
    List<CityButton>? listButtons;
    final FirebaseAuth auth = FirebaseAuth.instance;
    final User? user = auth.currentUser;
    final uid = user!.uid;
    CollectionReference trips = FirebaseFirestore.instance.collection('events');

    QuerySnapshot eventsQuery =
        await trips.where("uid", isEqualTo: uid).orderBy('initDate').get();
    // ignore: avoid_function_literals_in_foreach_calls
    eventsQuery.docs.forEach((element) {
      listButtons!.add(CityButton(
          element['city'],
          DateTime.parse(element['initDate']),
          DateTime.parse(element['endDate'])));
    });

    return ListView(
      children: listButtons!,
    );
  }


      @override
      Widget build(BuildContext context) {
        Future<ListView> lista = CreateList();
        
        return Scaffold(
          backgroundColor: const Color(0xFFF5F5F5),
          body: lista,

CodePudding user response：

CreateList() method is a future, use FutureBuilder

      @override
      Widget build(BuildContext context) {  
        return Scaffold(
          backgroundColor: const Color(0xFFF5F5F5),
          body: FutureBuilder<ListView>(
            future: CreateList(),
            builder: (context, snapshot) {
              if (snapshot.connectionState == ConnectionState.done &&
                  snapshot.hasData) {
                return snapshot.data!;
              } else {
             /// you handle others state like error while it will a widget no matter what, you can skip it
                return const CircularProgressIndicator();
              }
            },
          ),

CodePudding user response：

When you want to render widget after async then use FutureBuilder()

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: FutureBuilder<ListView>(
        future: CreateList(), // async work
        builder: (BuildContext context, AsyncSnapshot<ListView> snapshot) {
          switch (snapshot.connectionState) {
            case ConnectionState.waiting:
              return Text('Loading....');
            default:
              if (snapshot.hasError)
                return Text('Error: ${snapshot.error}');
              else
                return snapshot.data;
          }
        },
      ),
    );
  }