Flutter GraphQL请求插件mk

Flutter GraphQL请求插件mk_graphql的使用

在本示例中，我们将展示如何使用 mk_graphql 插件来发送 GraphQL 请求。mk_graphql 是一个用于处理 GraphQL 请求的 Flutter 插件。

示例代码

以下是一个完整的示例，展示了如何使用 mk_graphql 发送 GraphQL 查询并处理响应。

import 'dart:developer';

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

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

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  // 这个小部件是你的应用的根。
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  void initState() {
    super.initState();
    _request();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text(
              '你已经按了按钮这么多次：',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headlineMedium,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: '增加计数',
        child: const Icon(Icons.add),
      ),
    );
  }

  void _request() async {
    final client = GraphClient(
      GraphBaseOptions.fromBaseUrl('https://countries.trevorblades.com'),
      debug: true,
    );
    final response = await client.request(GraphRequest.fromString(_query));
    response.when(
      success: ((data, context, extensions) {
        log('数据 $data');
        log('上下文 $context');
        log('扩展信息 $extensions');
      }),
      error: (exception) {
        log('异常 $exception');
      },
    );
  }
}

const _query = r'''
{
  countries {
    code
    continent {
      code
      name
    }
  }
}''';

// 忽略：未使用的元素
const _mutation = r'''
mutation Insert_users($objects: [users_insert_input!]!) {
  insert_users(objects: $objects) {
    returning {
      id
      name
    }
  }
}
''';

代码解释

导入库：

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

导入 Flutter 框架和 mk_graphql 插件。

创建主应用：

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

定义主应用小部件：

class MyApp extends StatelessWidget {
  const MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
        useMaterial3: true,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

定义首页状态管理：

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

实现首页状态逻辑：

class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;

  void _incrementCounter() {
    setState(() {
      _counter++;
    });
  }

  @override
  void initState() {
    super.initState();
    _request();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            const Text(
              '你已经按了按钮这么多次：',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.headlineMedium,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: _incrementCounter,
        tooltip: '增加计数',
        child: const Icon(Icons.add),
      ),
    );
  }

  void _request() async {
    final client = GraphClient(
      GraphBaseOptions.fromBaseUrl('https://countries.trevorblades.com'),
      debug: true,
    );
    final response = await client.request(GraphRequest.fromString(_query));
    response.when(
      success: ((data, context, extensions) {
        log('数据 $data');
        log('上下文 $context');
        log('扩展信息 $extensions');
      }),
      error: (exception) {
        log('异常 $exception');
      },
    );
  }
}

定义 GraphQL 查询：

const _query = r'''
{
  countries {
    code
    continent {
      code
      name
    }
  }
}''';

定义 GraphQL 变更：

const _mutation = r'''
mutation Insert_users($objects: [users_insert_input!]!) {
  insert_users(objects: $objects) {
    returning {
      id
      name
    }
  }
}
''';

更多关于Flutter GraphQL请求插件mk_graphql的使用的实战教程也可以访问 https://www.itying.com/category-92-b0.html

yuanlaile 1楼

更多关于Flutter GraphQL请求插件mk_graphql的使用的实战系列教程也可以访问 https://www.itying.com/category-92-b0.html

当然，下面是一个关于如何在Flutter中使用mk_graphql插件进行GraphQL请求的示例代码。这个插件可以帮助你方便地在Flutter应用中执行GraphQL查询和变更操作。

1. 添加依赖

首先，你需要在pubspec.yaml文件中添加mk_graphql的依赖：

dependencies:
  flutter:
    sdk: flutter
  mk_graphql: ^最新版本号 # 请替换为实际发布的最新版本号

2. 初始化GraphQL客户端

在你的应用中初始化GraphQL客户端，通常你会在一个单独的Dart文件中配置客户端，例如graphql_client.dart：

import 'package:mk_graphql/mk_graphql.dart';

class GraphQLClient {
  final GraphQLClient _client;

  GraphQLClient(String endpoint) {
    _client = GraphQLClient(
      endpoint: endpoint,
      headers: <String, String>{
        'Content-Type': 'application/json',
        'Authorization': 'Bearer YOUR_AUTH_TOKEN', // 如果需要身份验证
      },
    );
  }

  GraphQLClient get client => _client;
}

3. 定义GraphQL查询

定义一个GraphQL查询，例如获取用户信息的查询：

const String getUserQuery = """
query GetUser($id: ID!) {
  user(id: $id) {
    id
    name
    email
  }
}
""";

4. 执行GraphQL请求

在你的Flutter组件中执行GraphQL请求并处理结果：

import 'package:flutter/material.dart';
import 'package:mk_graphql/mk_graphql.dart';
import 'graphql_client.dart';

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

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: UserScreen(),
    );
  }
}

class UserScreen extends StatefulWidget {
  @override
  _UserScreenState createState() => _UserScreenState();
}

class _UserScreenState extends State<UserScreen> {
  final GraphQLClient graphQLClient = GraphQLClient('https://your-graphql-endpoint.com/graphql');
  String userId = '1'; // 假设我们要查询的用户ID
  User? user;
  String errorMessage = '';

  @override
  void initState() {
    super.initState();
    fetchUser();
  }

  void fetchUser() async {
    var variables = <String, dynamic>{'id': userId};
    var request = GraphQLRequest(query: getUserQuery, variables: variables);
    
    try {
      var response = await graphQLClient.client.execute(request);
      if (response.hasErrors) {
        throw Exception(response.errors!.map((e) => e.message).join(', '));
      }
      
      var data = response.data!['user'];
      setState(() {
        user = User.fromJson(data as Map<String, dynamic>);
        errorMessage = '';
      });
    } catch (e) {
      setState(() {
        user = null;
        errorMessage = e.toString();
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('User Info'),
      ),
      body: Padding(
        padding: const EdgeInsets.all(16.0),
        child: Column(
          crossAxisAlignment: CrossAxisAlignment.start,
          children: [
            if (errorMessage.isNotEmpty)
              Text(
                errorMessage,
                style: TextStyle(color: Colors.red),
              ),
            if (user != null)
              Column(
                crossAxisAlignment: CrossAxisAlignment.start,
                children: [
                  Text('ID: ${user!.id}'),
                  Text('Name: ${user!.name}'),
                  Text('Email: ${user!.email}'),
                ],
              ),
          ],
        ),
      ),
    );
  }
}

class User {
  final String id;
  final String name;
  final String email;

  User({required this.id, required this.name, required this.email});

  factory User.fromJson(Map<String, dynamic> json) {
    return User(
      id: json['id'] as String,
      name: json['name'] as String,
      email: json['email'] as String,
    );
  }
}

注意事项

错误处理：确保在生产代码中处理各种可能的错误情况。
安全性：不要在客户端代码中硬编码敏感信息，如API密钥或用户令牌。
性能优化：对于大型数据集，考虑使用分页或懒加载等技术。

这个示例展示了如何使用mk_graphql插件在Flutter应用中执行GraphQL查询。你可以根据实际需要调整和扩展这个示例。