Flutter 未处理的异常：类型 &#39;_InternalLinkedHashMap<String, dynamic> JSON 请求

Question

I'm a beginner in flutter and i have problem with my app when i wanna take the values from the JSON.

The problem comes from my http request when i call GetCommands() and i don't know to solve it. I already did it once in another app with other data(JSON too) and it worked...

Here is the main code :

  var commandsGet = new List<Value>();

  Future<void> GetCommands() async {
    await GET.url(urlTest).then((response) {
      setState(() {
        Iterable list2 = json.decode(response.body);
        commandsGet = list2.map((model) => Value.fromJson(model)).toList();
      });
    });
  }

  Future<void> wait2() async {
    await GetCommands();
  }

  onChange2(commandsData user) {
    setState(() {
      commandselection = user;
      // TEST 
      wait2().then((result) {
        print("This is a test");
      });
      // TEST
    });
  }

Here is my Value class :

class Value {
  String device;
  int origin;
  List<Readings> readings;

  Value({
    this.device,
    this.origin,
    this.readings,
  });

  Value.fromJson(Map<String, dynamic> json) {
    device = json['device'];
    origin = json['origin'];
    if (json['readings'] != null) {
      readings = new List<Readings>();
      json['readings'].forEach((v) {
        readings.add(new Readings.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data2 = new Map<String, dynamic>();
    data2['device'] = this.device;
    data2['origin'] = this.origin;
    if (this.readings != null) {
      data2['readings'] = this.readings.map((v) => v.toJson()).toList();
    }
    return data2;
  }
}

And here is the the Debug console errors :

[VERBOSE-2:ui_dart_state.cc(157)] Unhandled Exception: type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'Iterable<dynamic>'
#0      _MyListScreenState.GetCommands.<anonymous closure>.<anonymous closure> 
package:chat/main.dart:92
#1      State.setState 
package:flutter/…/widgets/framework.dart:1164
#2      _MyListScreenState.GetCommands.<anonymous closure> 
#3      _rootRunUnary  (dart:async/zone.dart:1134:38)
#4      _CustomZone.runUnary  (dart:async/zone.dart:1031:19)
#5      _FutureListener.handleValue  (dart:async/future_impl.dart:140:18)
#6      Future._propagateToListeners.handleValueCallback  (dart:async/future_impl.dart:682:45)
#7      Future._propagateToListeners  (dart:async/future_impl.dart:711:32)
#8      Future._completeWithValue  (dart:async/future_impl.dart:526:5)
#9      _AsyncAwaitCompleter.complete  (dart:async-patch/async_patch.dart:34:15)
#10     _completeOnAsyncReturn  (dart:async-patch/async_patch.dart:293:13)
#11     _withCl<…>

Here is the JSON data :

{
    "device": "Random-Integer-Generator01",
    "origin": 1581956092184,
    "readings": [
        {
            "origin": 1581956092183,
            "device": "Random-Integer-Generator01",
            "name": "RandomValue_Int8",
            "value": "23"
        }
    ]
}

Thanks a lot for your help.

Answer 1

I think the problem is response.body , what is the type? If the response.body is map of String and dynamic already, you dont need to use json.decode , just Value.fromJson(model)

Try to modify, removing decode and parsing direct response.body to list like this:

(response.body as List).map((item) => Value.fromJson(item)).toList()

If not work, please, pass what package do you use to make http call.

I've tested with this url http://www.mocky.io/v2/5e4b0ef82f000000bc97d6ee and Dio package.