Exemplo de uso do future

future.dart

import 'package:flutter/material.dart';

class TesteWidget extends StatefulWidget {
  const TesteWidget({Key? key}) : super(key: key);

  @override
  _TesteWidgetState createState() => _TesteWidgetState();
}

class _TesteWidgetState extends State<TesteWidget> {
  Future<List> _future() {
    return Future.delayed(const Duration(seconds: 3), () {
      return [
        {"id": 1, "title": "teste 1"},
        {"id": 2, "title": "teste 2"}
      ];
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text("teste"),
        centerTitle: true,
      ),
      body: Center(
        child: FutureBuilder<List>(
          future: _future(),
          builder: (context, snapshot) {
            if (snapshot.connectionState == ConnectionState.done) {
              if (snapshot.hasData && snapshot.hasError == false) {
                return ListView.builder(
                  itemCount: snapshot.data!.length,
                  itemBuilder: (context, index) {
                    switch (snapshot.data![index]["id"]) {
                      case 1:
                        return ListTile(
                          title: Text(
                              "primeiro " + snapshot.data![index]["title"]),
                        );
                      case 2:
                        return ListTile(
                          title:
                              Text("segundo " + snapshot.data![index]["title"]),
                        );

                      default:
                        return const ListTile(
                          title: Text("padrao"),
                        );
                    }
                  },
                );
              } else {
                return const Text("erro");
              }
            } else {
              return const CircularProgressIndicator();
            }
          },
        ),
      ),
    );
  }
}