flutter - 如何在 Flutter 中使用自定义模型从 Future 中获取价值

Question

我正在调用一个 API 来从服务器获取数据，并且我已经从（https://javiercbk.github.io/json_to_dart/）创建了一个 dart 文件（模型）

现在我想访问那个未来的对象值。

主要.dart

@override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Row(
          children: <Widget>[
            RaisedButton(
              child: Text("Click"),
              onPressed: () async{
                setState(() {
                  apiCall = true; // Set state like this
                });
                MemberLogin fMain = await getUser();
                print('$fMain ');
              },
            ),
          ],
        ),
      ),
    );
  }

  Future<MemberLogin> getUser() async {
    try {
      final String _endpoint =
          "https://api.com/";
      Dio dio = new Dio();
      Response response = await dio
          .post(_endpoint, data: {"new_data": "hello"});
      print("user API response - : $response ");
      setState(() {
        apiCall = false;
      });
      return MemberLogin.fromJson(response.data);
    } catch (error, stacktrace) {
      print("Exception occured: $error stackTrace: $stacktrace");
      //return MemberLogin.withError("$error");
    }
  }

会员登录.dart

class MemberLogin {
  int success;
  String message;

  MemberLogin({this.success, this.message});

  MemberLogin.fromJson(Map<String, dynamic> json) {
    success = json['success'];
    message = json['message'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['success'] = this.success;
    data['message'] = this.message;
    return data;
  }
}

现在，当我在我的请求后打印message时。我已经调试了代码，我能够看到响应，但我无法打印或访问消息字符串。MemberLoginMemberLogin fMain = await getUser();

我怎样才能做到这一点 ？

Answer 1

@deepak，我模拟了一个 api，似乎工作正常。您是否尝试过访问消息fMain.message？请看下面的例子，

class MyAppState extends State<MyApp> {
  bool apiCall = false;
  String message = '';

  @override
  Widget build(BuildContext context) {
    return MaterialApp(home: Scaffold(
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(message, style: TextStyle(fontWeight: FontWeight.bold, fontSize: 18.0),),
            RaisedButton(
              child: Text("Click", style: TextStyle(fontWeight: FontWeight.bold, fontSize: 18.0),),
              onPressed: () async{
                apiCall = true; // Set state like this
                MemberLogin fMain = await getUser();
                message = fMain.message;
                setState(() {
                });
                print('$fMain ');
              },
            ),
          ],
        ),
      ),
    ));
  }

  Future<MemberLogin> getUser() async {
    try {
      final String _endpoint =
          "http://echo.jsontest.com/key/value/message/testmessage";
      Dio dio = new Dio();
      Response response = await dio
          .get(_endpoint);
      print("user API response - : $response ");
      setState(() {
        apiCall = false;
      });
      return MemberLogin.fromJson(response.data);
    } catch (error, stacktrace) {
      print("Exception occured: $error stackTrace: $stacktrace");
      //return MemberLogin.withError("$error");
    }
  }
}

class MemberLogin {
  String key;
  String message;

  MemberLogin({this.key, this.message});

  MemberLogin.fromJson(Map<String, dynamic> json) {
    key = json['key'];
    message = json['message'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['key'] = this.key;
    data['message'] = this.message;
    return data;
  }
}