Flutter空气质量查询插件air_quality_waqi的使用

当然，下面是一个关于如何使用Flutter中的air_quality_waqi插件来查询空气质量的示例代码。这个插件允许你访问World Air Quality Index (WAQI) API，获取实时空气质量数据。

首先，确保你的Flutter项目中已经添加了air_quality_waqi依赖。在pubspec.yaml文件中添加以下依赖：

dependencies:
  flutter:
    sdk: flutter
  air_quality_waqi: ^x.y.z  # 替换为最新版本号

然后运行flutter pub get来安装依赖。

接下来，我们编写一个示例Flutter应用，展示如何使用这个插件来查询某个城市的空气质量。

import 'package:flutter/material.dart';
import 'package:air_quality_waqi/air_quality_waqi.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Air Quality Checker',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: AirQualityScreen(),
    );
  }
}

class AirQualityScreen extends StatefulWidget {
  @override
  _AirQualityScreenState createState() => _AirQualityScreenState();
}

class _AirQualityScreenState extends State<AirQualityScreen> {
  String? cityName;
  AirQualityData? airQualityData;
  String? errorMessage;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Air Quality Checker'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: <Widget>[
            TextField(
              decoration: InputDecoration(
                labelText: 'Enter city name',
              ),
              onChanged: (value) {
                setState(() {
                  cityName = value;
                });
              },
            ),
            SizedBox(height: 16),
            ElevatedButton(
              onPressed: fetchAirQualityData,
              child: Text('Get Air Quality'),
            ),
            SizedBox(height: 16),
            if (errorMessage != null)
              Text(
                errorMessage!,
                style: TextStyle(color: Colors.red),
              ),
            if (airQualityData != null)
              Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: <Widget>[
                  Text('AQI: ${airQualityData!.aqi!.toInt()}'),
                  Text('City: ${airQualityData!.location!.city}'),
                  Text('Country: ${airQualityData!.location!.country}'),
                  Text('Pollutants: ${airQualityData!.iaqi!.values.map((e) => '${e.pollutant}: ${e.value.toInt()}').join(', ')}'),
                ],
              ),
          ],
        ),
      ),
    );
  }

  Future<void> fetchAirQualityData() async {
    if (cityName == null || cityName!.isEmpty) {
      setState(() {
        errorMessage = 'Please enter a city name';
        airQualityData = null;
      });
      return;
    }

    try {
      final AirQualityWaqi airQualityWaqi = AirQualityWaqi(apiKey: 'YOUR_API_KEY'); // 替换为你的API Key
      final AirQualityResponse response = await airQualityWaqi.getAirQualityByCityName(cityName!);
      setState(() {
        errorMessage = null;
        airQualityData = response.data;
      });
    } catch (e) {
      setState(() {
        errorMessage = 'Failed to fetch air quality data: ${e.toString()}';
        airQualityData = null;
      });
    }
  }
}

class AirQualityData {
  final int? aqi;
  final Location? location;
  final Iaqi? iaqi;

  AirQualityData({this.aqi, this.location, this.iaqi});

  factory AirQualityData.fromJson(Map<String, dynamic> json) {
    return AirQualityData(
      aqi: json['aqi'] as int?,
      location: json['location'] != null ? Location.fromJson(json['location'] as Map<String, dynamic>) : null,
      iaqi: json['iaqi'] != null ? Iaqi.fromJson(json['iaqi'] as Map<String, dynamic>) : null,
    );
  }
}

class Location {
  final String? city;
  final String? country;

  Location({this.city, this.country});

  factory Location.fromJson(Map<String, dynamic> json) {
    return Location(
      city: json['name'] as String?,
      country: json['country'] as String?,
    );
  }
}

class Iaqi {
  final List<IaqiValue> values;

  Iaqi({required this.values});

  factory Iaqi.fromJson(Map<String, dynamic> json) {
    List<IaqiValue> values = [];
    json['o3']?.forEach((key, value) {
      values.add(IaqiValue(pollutant: key, value: value as num));
    });
    // 根据实际返回的JSON结构，可能需要添加对其他污染物的处理
    return Iaqi(values: values);
  }
}

class IaqiValue {
  final String pollutant;
  final num value;

  IaqiValue({required this.pollutant, required this.value});
}

class AirQualityResponse {
  final AirQualityData? data;

  AirQualityResponse({this.data});

  factory AirQualityResponse.fromJson(Map<String, dynamic> json) {
    return AirQualityResponse(
      data: json['data'] != null ? AirQualityData.fromJson(json['data'] as Map<String, dynamic>) : null,
    );
  }
}

注意：

1. 替换YOUR_API_KEY为你从WAQI官网获取的API Key。
2. 上述代码中的AirQualityData、Location、Iaqi和IaqiValue类是为了方便解析API返回的数据结构。实际的JSON结构可能会有所不同，你可能需要根据实际的API响应调整这些类的定义。
3. 由于API可能会返回多种污染物数据，示例中只解析了o3（臭氧）的数据作为示例。你可能需要添加对其他污染物的处理。

这个示例应用允许用户输入城市名称，然后点击按钮查询该城市的空气质量数据，并在界面上显示结果。