如何将 JSON 响应转换为 Dart Map<String, int> object ...？答案

【问题标题】：How to convert JSON response to Dart Map<String, int> object ...?如何将 JSON 响应转换为 Dart Map<String, int> object ...？
【发布时间】：2021-02-05 02:49:14
【问题描述】：

我从我的 api 获取数据作为以下 JSON 对象，以使用数据创建图表。我想将此 DIO 响应转换为我的颤振应用程序中的 Map 对象。

我的 API 响应：

{
    "November 20": 1,
    "October 20": 3,
    "September 20": 1
}

我尝试创建地图对象：

  Future<bool> fetchChartData() async {
    var response = await CasesApiService().getChartData();
    Map<String, dynamic> data = jsonDecode(response.data);
  }

但它显示以下错误：

E/flutter ( 4733): [ERROR:flutter/lib/ui/ui_dart_state.cc(177)] Unhandled Exception: type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'String'
E/flutter ( 4733): #0      CasesProvider.fetchChartData
package:bdopsApp/providers/casesProvider.dart:86
E/flutter ( 4733): <asynchronous suspension>
E/flutter ( 4733): #1      _CasesChartViewState.build.<anonymous closure>
package:bdopsApp/…/casesApp/casesChart.dart:31
E/flutter ( 4733): #2      _InkResponseState._handleTap
package:flutter/…/material/ink_well.dart:985
E/flutter ( 4733): #3      _InkResponseState.build.<anonymous closure>
package:flutter/…/material/ink_well.dart:1101
E/flutter ( 4733): #4      GestureRecognizer.invokeCallback
package:flutter/…/gestures/recognizer.dart:183
E/flutter ( 4733): #5      TapGestureRecognizer.handleTapUp
package:flutter/…/gestures/tap.dart:598
E/flutter ( 4733): #6      BaseTapGestureRecognizer._checkUp
package:flutter/…/gestures/tap.dart:287
E/flutter ( 4733): #7      BaseTapGestureRecognizer.handlePrimaryPointer
package:flutter/…/gestures/tap.dart:222
E/flutter ( 4733): #8      PrimaryPointerGestureRecognizer.handleEvent
package:flutter/…/gestures/recognizer.dart:476
E/flutter ( 4733): #9      PointerRouter._dispatch
package:flutter/…/gestures/pointer_router.dart:77
E/flutter ( 4733): #10     PointerRouter._dispatchEventToRoutes.<anonymous closure>
package:flutter/…/gestures/pointer_router.dart:122
E/flutter ( 4733): #11     _LinkedHashMapMixin.forEach (dart:collection-patch/compact_hash.dart:377:8)
E/flutter ( 4733): #12     PointerRouter._dispatchEventToRoutes
package:flutter/…/gestures/pointer_router.dart:120
E/flutter ( 4733): #13     PointerRouter.route
package:flutter/…/gestures/pointer_router.dart:106
E/flutter ( 4733): #14     GestureBinding.handleEvent
package:flutter/…/gestures/binding.dart:368
E/flutter ( 4733): #15     GestureBinding.dispatchEvent
package:flutter/…/gestures/binding.dart:348
E/flutter ( 4733): #16     RendererBinding.dispatchEvent
package:flutter/…/rendering/binding.dart:268
E/flutter ( 4733): #17     GestureBinding._handlePointerEventImmediately
package:flutter/…/gestures/binding.dart:303
E/flutter ( 4733): #18     GestureBinding.handlePointerEvent
package:flutter/…/gestures/binding.dart:267
E/flutter ( 4733): #19     GestureBinding._flushPointerEventQueue
package:flutter/…/gestures/binding.dart:225
E/flutter ( 4733): #20     GestureBinding._handlePointerDataPacket
package:flutter/…/gestures/binding.dart:208
E/flutter ( 4733): #21     _rootRunUnary (dart:async/zone.dart:1206:13)
E/flutter ( 4733): #22     _CustomZone.runUnary (dart:async/zone.dart:1100:19)
E/flutter ( 4733): #23     _CustomZone.runUnaryGuarded (dart:async/zone.dart:1005:7)
E/flutter ( 4733): #24     _invoke1 (dart:ui/hooks.dart:265:10)
E/flutter ( 4733): #25     _dispatchPointerDataPacket (dart:ui/hooks.dart:174:5)

注意： 我正在做我最后一年的项目。因此，我所遵循的过程可能不是实际项目中使用的。

【问题讨论】：

您确定上面提到的代码 sn-p 会引发该错误吗？ .
如果是，那么可能尝试将解码值作为 Map 或只是一个 var ......所以首先尝试： Map data = jsonDecode( ...) 如果这也引发错误，请尝试 var data = jsonDecode(.....)

标签： flutter dart

【解决方案1】：

如果您在dartPad 中运行以下示例，您将得到您正在寻找的结果：

import 'dart:convert';

void main() {
  
  var jsonString= "{\"November 20\": \"1\",\"October 20\": \"2\",\"September 20\": \"3\"}";
  Map<String, dynamic> data = jsonDecode(jsonString);
  
  print(data);
}

我认为您需要检查从 response.data

获取的数据

【讨论】：