fcm_subscribed_topics 是一个用于管理 Firebase Cloud Messaging (FCM) 主题订阅的 Flutter 插件。它允许你在应用中订阅和取消订阅 FCM 主题，以便接收与这些主题相关的推送通知。

安装插件

首先，你需要在 pubspec.yaml 文件中添加 fcm_subscribed_topics 插件的依赖：

dependencies:
  flutter:
    sdk: flutter
  fcm_subscribed_topics: ^1.0.0  # 请检查最新版本

然后运行 flutter pub get 来安装插件。

初始化 FCM

在使用 fcm_subscribed_topics 之前，你需要确保已经正确初始化了 FCM。通常，你需要在 main.dart 中初始化 FCM：

import 'package:firebase_core/firebase_core.dart';
import 'package:firebase_messaging/firebase_messaging.dart';

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  
  FirebaseMessaging messaging = FirebaseMessaging.instance;

  // 请求通知权限
  NotificationSettings settings = await messaging.requestPermission(
    alert: true,
    badge: true,
    sound: true,
  );

  // 获取 FCM 令牌
  String? token = await messaging.getToken();
  print("FCM Token: $token");

  runApp(MyApp());
}

使用 fcm_subscribed_topics 插件

订阅主题

要订阅一个 FCM 主题，你可以使用 FcmSubscribedTopics 的 subscribeToTopic 方法：

import 'package:fcm_subscribed_topics/fcm_subscribed_topics.dart';

void subscribeToTopic(String topic) async {
  try {
    await FcmSubscribedTopics.subscribeToTopic(topic);
    print("Subscribed to topic: $topic");
  } catch (e) {
    print("Failed to subscribe to topic: $e");
  }
}

取消订阅主题

要取消订阅一个 FCM 主题，你可以使用 FcmSubscribedTopics 的 unsubscribeFromTopic 方法：

void unsubscribeFromTopic(String topic) async {
  try {
    await FcmSubscribedTopics.unsubscribeFromTopic(topic);
    print("Unsubscribed from topic: $topic");
  } catch (e) {
    print("Failed to unsubscribe from topic: $e");
  }
}

获取已订阅的主题

你可以使用 FcmSubscribedTopics 的 getSubscribedTopics 方法来获取当前设备已订阅的主题列表：

void getSubscribedTopics() async {
  try {
    List<String> topics = await FcmSubscribedTopics.getSubscribedTopics();
    print("Subscribed topics: $topics");
  } catch (e) {
    print("Failed to get subscribed topics: $e");
  }
}

示例代码

以下是一个简单的示例，展示了如何在 Flutter 应用中使用 fcm_subscribed_topics 插件来管理 FCM 主题订阅：

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

void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(
          title: Text('FCM Topics Example'),
        ),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              ElevatedButton(
                onPressed: () => subscribeToTopic('example_topic'),
                child: Text('Subscribe to Topic'),
              ),
              ElevatedButton(
                onPressed: () => unsubscribeFromTopic('example_topic'),
                child: Text('Unsubscribe from Topic'),
              ),
              ElevatedButton(
                onPressed: getSubscribedTopics,
                child: Text('Get Subscribed Topics'),
              ),
            ],
          ),
        ),
      ),
    );
  }

  void subscribeToTopic(String topic) async {
    try {
      await FcmSubscribedTopics.subscribeToTopic(topic);
      print("Subscribed to topic: $topic");
    } catch (e) {
      print("Failed to subscribe to topic: $e");
    }
  }

  void unsubscribeFromTopic(String topic) async {
    try {
      await FcmSubscribedTopics.unsubscribeFromTopic(topic);
      print("Unsubscribed from topic: $topic");
    } catch (e) {
      print("Failed to unsubscribe from topic: $e");
    }
  }

  void getSubscribedTopics() async {
    try {
      List<String> topics = await FcmSubscribedTopics.getSubscribedTopics();
      print("Subscribed topics: $topics");
    } catch (e) {
      print("Failed to get subscribed topics: $e");
    }
  }
}