Flutter-WebSocket策略

一，程序入口绑定url

void main() async {
  ...
  WebSocketManager().url = XXConfig.webSocketAlphaUrl;
 ...
  runApp(config);
}

二，登录成功后注册WebSocket，比如在TabPage中

 @override
  void initState() {
    super.initState();
    ...
    // 创建链接
    if (context.mounted) {
      WebSocketManager().connect(context: context);
    }
  }
@override
  void dispose() {
    super.dispose();
    WebSocketManager().close();
  }
@override
  void didChangeAppLifecycleState(AppLifecycleState state) {
    if (state == AppLifecycleState.resumed) {
      print("应用回到前台");
      WebSocketManager().checkConnect();
    } else if (state == AppLifecycleState.paused) {
      print("应用退到后台");
    } else if (state == AppLifecycleState.detached) {
      print("应用退出");
    }
  }

三，WebSocketManager中实现逻辑

心跳间隔3秒；
断连后重连，重连间隔3秒，次数最大10次，达到最大时倒计时100秒后重连；
发送特定连接前判断连接状态；
只维持一个计时器

class WebSocketManager {
  static WebSocketManager? _instance;
  static WebSocketChannel? _channel;
  String? roomId = "";
  String url = "";

  ///timer
  int _countdown = 3; // 心跳计时数
  int _reCountdown = 0; // 重连计时数
  static Timer? _countdownTimer; // 计时器
  /// 重连次数上限
  final int MAX_RECONNECT_ATTEMPTS = 10;
   /// 重连次数
  int _reconnectAttempts = 0;
  bool lockReconnect = false;
  String? token = "";
  BuildContext? context;

  factory WebSocketManager() {
    _instance ??= WebSocketManager._();
    return _instance!;
  }

  WebSocketManager._();

  ///判断是否断开，断开重连
  void checkConnect() {
    if (_channel == null) {
      _reconnectAttempts = 0;
      reConnect();
    }
  }

  /// 连接
  void connect({BuildContext? context}) {
    if (context != null) {
      ///初次链接
      this.context = context;
      token = UserManager.instance.userInfo?.token;
    }
    /// 判断是否已经连接
    if (_channel != null) {
      print("已经连接,请勿重新连接");
      return;
    }
    /// 连接
    _channel = WebSocketChannel.connect(
      Uri.parse(url),
    );
    /// 开始计时器
    startRecordTime();
    
    _countdown = 3;
    
    /// 收到消息
    onMessage.listen((message) {
      _reconnectAttempts = 0;
      // 处理接收到的消息
      handleMessage(message);
    }, onError: (error) {
      print("连接服务器失败error=$error");
      reConnect();
    } ,onDone: () {
      print("重连");
      reConnect();
    });
  }
  /// 重连
  void reConnect() {
    if (_reconnectAttempts >= MAX_RECONNECT_ATTEMPTS) {
      print("重连次数已达上限");
      _reCountdown = 100;
      _reconnectAttempts = 0;
      return;
    }
    if (lockReconnect) {
      return;
    }
    lockReconnect = true;
    _reCountdown = 3;
  }

  void reConnectAction() {
    // 关闭之前的连接
      close();
      // 重连次数加一
      _reconnectAttempts++;
      //重连
      connect();
      lockReconnect = false;
      print("重连次数:${_reconnectAttempts}");
  }

  // 发送心跳
  void sendLink() {
    if ((token?.length ?? 0) > 0) {
      Map<String, dynamic> map = {
        "Authorization": "Bearer $token",
        "code": 10000,
        "data": {"prescriptionOrderId": roomId ?? ""}
      };
      _channel?.sink.add(jsonEncode(map));
    }
  }

  // 进入处方编辑
  void sendEnterEdit(String id, BuildContext context) {
    if (_channel == null) {
      connect();
      sendEnterEdit(id, context);
      return;
    }
    var token = UserManager.instance.userInfo?.token;
    Map<String, dynamic> map = {
      "Authorization": "Bearer $token",
      "code": 10101,
      "data": {"prescriptionOrderId": id}
    };
    roomId = id;
    _channel?.sink.add(jsonEncode(map));

    print("-=-=======map${map}");

  }

  // 离开房间
  void sendLeaveEdit( BuildContext context) {
    if (_channel == null) {
      connect();
      sendLeaveEdit(context);
      return;
    }
    if (roomId == "") {
      return;
    }
    var token = UserManager.instance.userInfo?.token;
    Map<String, dynamic> map = {
      "Authorization": "Bearer $token",
      "code": 10102,
      "data": {"prescriptionOrderId": roomId}
    };
    roomId = "";
    _channel?.sink.add(jsonEncode(map));

    print("-=-=-========-=-=-=-=map: ${map}");

  }

  // 处理接收到的消息
  void handleMessage(dynamic message) {
    print(DateTime.now().toString().substring(11, 19)+ "------------------心跳------:" + message.toString());
    WebSocketBean bean = WebSocketBean.fromJson(jsonDecode(message));
    /// 正常则心跳
    if (bean.code == 100001) {
      _countdown = 3;
    } else if (bean.code == 10000) {
      reConnect();
    }  else if (bean.code == 100002) {
      if (context != null) {
        if (context!.mounted) {
          UserManager.instance.clearCache();
          context!.removeAndPush(LoginRouterName.login);
        }
      }
    } else {
      XxEventBus.instance().fire(WebSocketNotification(bean));
    }
  }
  ///开始心跳
  void startRecordTime() {
    if (_countdownTimer != null) {
      return;
    }
    _countdownTimer = Timer.periodic(const Duration(seconds: 1), (timer) {
      if (_countdown <= 1) {
        sendLink();
      } else {
        _countdown -= 1;
      }

      if (_reCountdown == 1) {
        reConnectAction();
        _reCountdown = 0;
      } else if (_reCountdown > 1) {
        _reCountdown -= 1;
      }
    });
  }

  Stream<dynamic> get onMessage => _channel?.stream ?? Stream.empty();

  void close() {
    _channel?.sink.close();
    _countdownTimer?.cancel();
    _countdownTimer = null;
    _channel = null;
  }
}

四，退出登录时close

 WebSocketManager().close();

五，wss：需要过滤签名认证

Android：
在android/app/src/main/res/xml/下创建network_security_config.xml文件
network_security_config.xml：

<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
    <base-config cleartextTrafficPermitted="true" />
    <domain-config cleartextTrafficPermitted="true">
        <domain includeSubdomains="true">wss://ws_ass_alpha.xiaoroujiankang.com</domain>
         <domain includeSubdomains="true">wss://ws_ass.xiaoroujiankang.com</domain>
    </domain-config>
</network-security-config>

AndroidManifest.xml文件中添加

<manifest xmlns:android="http://schemas.android.com/apk/res/android">
    <application
        android:label="*****"
        android:networkSecurityConfig="@xml/network_security_config"
    ...