json - Flutter 错误 : Expected a value of type 'FutureOr>' , 但得到了 '_JsonMap' 类型之一

Question

当我尝试解码 JSON 时，出现此错误:

Expected a value of type 'FutureOr<List>', but got one of type '_JsonMap'

这是我从 API 获取数据的代码:

Future<List> getData() async {
    final prefs = await SharedPreferences.getInstance();
    final key = 'token';
    final value = prefs.get(key) ?? 0;

    String myUrl = "$serverUrl/userchecks";
    http.Response response = await http.get(Uri.parse(myUrl), headers: {
      'Accept': 'application/json',
      'Authorization': 'Bearer $value'
    });

    print('Response status : ${response.statusCode}');

    return json.decode(response.body);
  }

Answer 1

您从 JSON 返回的值不是列表，而是一个 JSON 映射，因此您必须像这样更改 Future 返回类型:

Future<Map<String,dynamic>> getData() async {
    final prefs = await SharedPreferences.getInstance();
    final key = 'token';
    final value = prefs.get(key) ?? 0;

    String myUrl = "$serverUrl/userchecks";
    http.Response response = await http.get(Uri.parse(myUrl), headers: {
      'Accept': 'application/json',
      'Authorization': 'Bearer $value'
    });

    print('Response status : ${response.statusCode}');

    return json.decode(response.body);
  }

或者您可以按照答案进行操作 here .