添加事件监听

如需收到消息和事件通知，你需要先实现事件监听程序，然后订阅或者加入你想要接收消息或事件通知的频道。

添加事件监听

RTM 采用统一入口的方式处理消息和事件通知，每一种消息和事件通知都有对应的事件处理程序入口，你可以在其中实现自己的业务处理逻辑：

TypeScript

import {
  MessageEvent,
  PresenceEvent,
  TopicEvent,
  StorageEvent,
  LockEvent,
  LinkStateEvent,
  TokenEvent
} from '@shengwang/rtm-full';

// Handle message event
rtmClient.addEventListener('message', (event: object) => {
  const msgEvent = event as MessageEvent;
  const channelType = msgEvent.channelType;      // The channel type: MESSAGE or STREAM
  const channelName = msgEvent.channelName;      // The name of the channel
  const topic = msgEvent.channelTopic;           // (Stream channel only) The topic name
  const messageType = msgEvent.messageType;      // The message type: STRING or BINARY
  const customType = msgEvent.customType;        // User defined type
  const publisher = msgEvent.publisher;          // Message publisher
  const message = msgEvent.message;              // Message payload (string or Uint8Array)
  const timestamp = msgEvent.timestamp;          // Event timestamp
  // Your business logic
});

// Handle presence event
rtmClient.addEventListener('presence', (event: object) => {
  const presenceEvent = event as PresenceEvent;
  const eventType = presenceEvent.eventType;          // Event type: SNAPSHOT, INTERVAL, JOIN, LEAVE, etc.
  const channelType = presenceEvent.channelType;      // Channel type: MESSAGE or STREAM
  const channelName = presenceEvent.channelName;      // Channel name
  const publisher = presenceEvent.publisher;          // Who triggered this event
  const stateChanged = presenceEvent.stateChanged;    // Changed state items
  const interval = presenceEvent.interval;            // Interval info (only for INTERVAL type)
  const snapshot = presenceEvent.snapshot;            // Snapshot info (only for SNAPSHOT type)
  const timestamp = presenceEvent.timestamp;          // Event timestamp
  // Your business logic
});

// Handle topic event
rtmClient.addEventListener('topic', (event: object) => {
  const topicEvent = event as TopicEvent;
  const eventType = topicEvent.eventType;          // Event type: SNAPSHOT, REMOTE_JOIN, REMOTE_LEAVE
  const channelName = topicEvent.channelName;      // Channel name
  const publisher = topicEvent.publisher;          // Who triggered this event
  const topicInfos = topicEvent.topicInfos;        // Topic information array
  const timestamp = topicEvent.timestamp;          // Event timestamp
  // Your business logic
});

// Handle storage event
rtmClient.addEventListener('storage', (event: object) => {
  const storageEvent = event as StorageEvent;
  const eventType = storageEvent.eventType;          // Event type: SNAPSHOT, SET, UPDATE, REMOVE
  const storageType = storageEvent.storageType;      // Storage type: USER or CHANNEL
  const channelType = storageEvent.channelType;      // Channel type (for channel metadata)
  const target = storageEvent.target;                // Channel name or user ID
  const data = storageEvent.data;                    // Metadata
  const timestamp = storageEvent.timestamp;          // Event timestamp
  // Your business logic
});

// Handle lock event
rtmClient.addEventListener('lock', (event: object) => {
  const lockEvent = event as LockEvent;
  const eventType = lockEvent.eventType;          // Event type: SNAPSHOT, LOCK_SET, LOCK_ACQUIRED, etc.
  const channelName = lockEvent.channelName;      // Channel name
  const channelType = lockEvent.channelType;      // Channel type
  const lockDetails = lockEvent.lockDetails;      // Lock details array
  const timestamp = lockEvent.timestamp;          // Event timestamp
  // Your business logic
});

// Handle link state event
rtmClient.addEventListener('linkState', (event: object) => {
  const linkEvent = event as LinkStateEvent;
  const currentState = linkEvent.currentState;    // Current link state
  const previousState = linkEvent.previousState;  // Previous link state
  const serviceType = linkEvent.serviceType;      // Service type: MESSAGE or STREAM
  const operation = linkEvent.operation;          // Operation that triggered this event
  const reason = linkEvent.reason;                // Reason description
  const affectedChannels = linkEvent.affectedChannels;      // Affected channels
  const unrestoredChannels = linkEvent.unrestoredChannels;  // Unrestored channels
  const isResumed = linkEvent.isResumed;          // Whether connection is resumed
  const timestamp = linkEvent.timestamp;          // Event timestamp
  // Your business logic
});

// Handle token event
rtmClient.addEventListener('token', (event: object) => {
  const tokenEvent = event as TokenEvent;
  const eventType = tokenEvent.eventType;          // Token event type
  const reason = tokenEvent.reason;                // Event reason
  const affectedResources = tokenEvent.affectedResources;  // Affected resources
  const timestamp = tokenEvent.timestamp;          // Event timestamp
  // Your business logic
});

删除事件监听

为避免内存泄漏、错误和异常（即空指针异常）引起的性能下降，声网建议你在不需要使用某个事件处理程序时对其进行注销。如需注销事件监听程序，则需在添加事件监听时避免采用匿名函数的方式，以下是添加和注销事件监听程序的示例代码。

TypeScript

import { MessageEvent } from '@shengwang/rtm-full';

// Define message event handler function
const onMessageReceived = (event: object) => {
  const msgEvent = event as MessageEvent;
  console.log('Received message event:', msgEvent);
  // Your business logic
};

// Add event listener
rtmClient.addEventListener('message', onMessageReceived);

// Remove event listener
rtmClient.removeEventListener('message', onMessageReceived);

事件通知类型

RTM 一共有 7 种类型事件，对应的有 7 种事件监听程序。你可以查看 API 参考的事件监听章节，了解每个事件监听程序传入参数的详细信息。

事件监听程序	描述
message	接收所有订阅的 Message Channel 中的消息通知或你加入的所有 Stream Channel 中订阅的 Topic 消息通知。事件负载数据中包含频道名称、频道类型、Topic 名称、事件发送者、消息负载数据类型等信息。
presence	接收所有订阅的 Message Channel 或者你加入的所有 Stream Channel 中远端用户的在线状态事件通知。事件负载数据中包含频道名称、频道类型、事件类型、事件发送者、用户临时状态数据等信息。
topic	接收加入的所有 Stream Channel 中 Topic 变更事件通知。事件负载数据中包含频道名称、事件类型、Topic 名称、事件发送者（即 Topic 详情）等信息。
storage	接收订阅的 Message Channel 及加入的 Stream Channel 中所有的 Channel Metadata 事件通知，以及所有订阅用户的 User Metadata 事件通知。事件负载数据中包含频道名称、频道类型、事件类型（即具体 Metadata 数据）等信息。
lock	接收订阅的 Message Channel 及加入的 Stream Channel 中所有的 Lock 事件通知。事件负载数据中包含有频道名称、频道类型、事件类型、锁详情等信息。
linkState	接收客户端网络连接状态变更的事件通知，包含变更前后的连接状态、服务类型、导致变更的操作类型、变更原因、频道列表等信息。
token	接收客户端 Token 将要过期的事件通知。

完成事件监听处理程序后，你可以通过订阅频道或 Topic 来接收指定的 Message Channel 或 Stream Channel 中的消息和事件通知了。详见订阅 Message Channel 和订阅 Topic。