错误:NoSuchMethodError:方法"toDouble"在null上被调用.接收方:null尝试调用:toDouble()

本文介绍了错误:NoSuchMethodError:方法"toDouble"在null上被调用.接收方:null尝试调用:toDouble()的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我正在尝试使用fromJson函数来解析json文件.但是在运行测试时，我收到此错误消息.

错误:NoSuchMethodError:方法'toDouble'在null上调用.接收者:null尝试调用:toDouble()

我不确定这是怎么回事.

我的代码

weather_model_app_test.dart

group('fromJson'，(){测试(应返回有效模型"，()异步{最终Map< String，dynamic>jsonMap =json.decode(fixture('weather_app.json'));//行为最终结果= WeatherAppModel.fromJson(jsonMap);//断言Expect(结果，tWeatherAppModel);});});

weather_app_model.dart

工厂WeatherAppModel.fromJson(Map< String，dynamic> json){返回WeatherAppModel(weatherMain:json ['weather'] [0] ['main']，weatherDescription:json ['weather'] [0] ['description']，temp:(json ['main'] ['temp']为double).toDouble()，minTemp:(json ['main'] ['temp_min']为double).toDouble()，maxTemp:(json ['main'] ['temp_main']为double).toDouble()，国家/地区:json ['sys'] ['country']，);}

fixtures/weather_app.dart

{"coord":{"lon":78，"lat":20}，天气": [{"id":500，"main":雨"，"description":小雨"，"icon":"10d"}]，"base":"model"，主要的": {温度":301.51，压力":1014，湿度":67，"temp_min":301.51，"temp_max":301.51，海平面":1014，"grnd_level":979}，风": {速度":3.19，度":77}，雨": {"3小时":1.81}，云":{全部":45}，"dt":1577262029，"sys":{"country":"IN"，日出":1572655775，日落":1572696807}，时区":19800，"id":1272596，"name":"Digras"，鳕鱼":200}

解决方案

不应 maxTemp:(json ['main'] ['temp_main'] as double).toDouble()，

在您的weather_app_model.dart文件中是 [temp_max] 而不是 [temp_main] ?

I am trying to make fromJson function which parse the json file. But while running test I am getting this error saying.

ERROR: NoSuchMethodError: The method 'toDouble' was called on null. Receiver: null Tried calling: toDouble()

I am not sure what is wrong with this.

My code

weather_model_app_test.dart

group('fromJson', () { test('should return a valid model', () async { final Map<String, dynamic> jsonMap = json.decode(fixture('weather_app.json')); //act final result = WeatherAppModel.fromJson(jsonMap); //assert expect(result, tWeatherAppModel); }); });

weather_app_model.dart

factory WeatherAppModel.fromJson(Map<String, dynamic> json) { return WeatherAppModel( weatherMain: json['weather'][0]['main'], weatherDescription: json['weather'][0]['description'], temp: (json['main']['temp'] as double).toDouble(), minTemp: (json['main']['temp_min'] as double).toDouble(), maxTemp: (json['main']['temp_main'] as double).toDouble(), country: json['sys']['country'], ); }

fixtures/weather_app.dart

{ "coord": { "lon": 78, "lat": 20 }, "weather": [ { "id": 500, "main": "Rain", "description": "light rain", "icon": "10d" } ], "base": "model", "main": { "temp": 301.51, "pressure": 1014, "humidity": 67, "temp_min": 301.51, "temp_max": 301.51, "sea_level": 1014, "grnd_level": 979 }, "wind": { "speed": 3.19, "deg": 77 }, "rain": { "3h": 1.81 }, "clouds": { "all": 45 }, "dt": 1572672029, "sys": { "country": "IN", "sunrise": 1572655775, "sunset": 1572696807 }, "timezone": 19800, "id": 1272596, "name": "Digras", "cod": 200 }

解决方案

Shouldn't maxTemp: (json['main']['temp_main'] as double).toDouble(),

be [temp_max] instead of [temp_main] in your weather_app_model.dart file?