Question

我正在尝试使用FutureBuilder显示无限列表。我想在不同的.dart文件中使用模型和服务，因此我需要在FutureBuilder中注入服务。我认为服务无法返回列表的问题，但我不知道为什么。代码是

模型

class Datameter {
  int idAgrupacion;
  int nroSerie;
  String fecha;

  ///
  double latitud;
  double longitud;
  String contador;
  String sensor;

  Datameter(
      {this.idAgrupacion,
      this.nroSerie,
      this.fecha,

      ///
      this.latitud,
      this.longitud,
      this.contador,
      this.sensor});

  factory Datameter.fromJson(json) => new Datameter(
        nroSerie: json["nro_serie"],
        idAgrupacion: json["id_agrupacion"],
        fecha: json["fecha"],
        //
        latitud: json["latitud"],
        longitud: json["longitud"],
        contador: json["contador"],
        sensor: json["sensor"],
      );
}

服务

  static Future<Datameter> getDatameters(dropdown) async {
    SharedPreferences prefs = await SharedPreferences.getInstance();
    final token = prefs.getString('token');
    final response = await http.get(
        'http://192.168.3.64:8080/datameter/agrupacion/info?agrupacion=' +
            dropdown +
            '&limite=0',
        headers: {
          HttpHeaders.authorizationHeader: "Token " + token
        }).catchError((error) {
      print(error.toString());
    });
      if (response.statusCode == 200) {
      var responseJson = json.decode(response.body);
      return responseJson["body"].map((item) => Datameter.fromJson(item)).toList();
    }
    return null;
  }

查看

FutureBuilder(
          future: DatameterService.getInstalations("2"),
          builder: (context, snapshot) {
            if (snapshot.connectionState == ConnectionState.done) {
              return snapshot.data;  ListView.separated(
                  separatorBuilder: (context, index) => Divider(
                        color: Colors.grey,
                      ),
                  itemCount: snapshot.data.length,
                  itemBuilder: (context, i) {
                    return ListTile(
                        leading: Icon(FontAwesomeIcons.tint,
                            size: 24, color: Colors.black),
                        trailing: Text(DateFormat('yyyy/MM/dd HH:mm')
                            .format(DateTime.fromMillisecondsSinceEpoch(
                                snapshot.data[i]['fecha']))
                            .toString()),
                        onTap: null,
                        title: Text(
                          snapshot.data[i]['nro_serie'],
                        ));
                  });
            } else {
              return CircularProgressIndicator();
            }
          }),

问题：返回'type DatameterList 类型不是'Widget'类型的子类型

所以：使用FutureBuilder显示列表的最正确方法是什么？

Answer 1

builder函数应该返回一个Widget，就像您已经注释掉的一样：

 FutureBuilder(
      future: DatameterService.getInstalations("2"),
      builder: (context, snapshot) {
        if (snapshot.connectionState == ConnectionState.done) {
          return ListView.separated(
              separatorBuilder: (context, index) => Divider(
                  color: Colors.grey,
              ),
              itemCount: snapshot.data.length,
              itemBuilder: (context, i) {
                return ListTile(
                    leading: Icon(FontAwesomeIcons.tint, size: 24, color: Colors.black),
                    trailing: Text(DateFormat('yyyy/MM/dd HH:mm')
                        .format(DateTime.fromMillisecondsSinceEpoch(
                            snapshot.data[i]['fecha'])
                        ).toString()
                    ),
                    onTap: null,
                    title: Text(
                      snapshot.data[i]['nro_serie'],
                    ),
                  );
              });
        } else {
          return CircularProgressIndicator();
        }
      }),

Flutter-具有服务和模型的Future Builder

1 个答案: