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Advanced features provide developers with the ability to extend WuKongIM HarmonyOS SDK, including custom message types, message extensions, message receipts and other enterprise-level features.
In WuKongIM, all message types are custom messages

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Custom Messages

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Custom Regular Messages

Below we use business card messages as an example.

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Step 1: Define Message

Define a message object that inherits from WKMessageContent and specify the message type in the constructor. 
// Define business card message
export class CardMessageContent extends WKMessageContent {
  uid: string = '';
  name: string = '';
  avatar: string = '';
  
  constructor() {
    super();
    this.contentType = 16; // Specify type
  }
}

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Step 2: Encoding and Decoding

We need to send uid, name, avatar three field information to the recipient. The final message content passed is: 
{
  "type": 16,
  "uid": "xxxx",
  "name": "xxx",
  "avatar": "xxx"
}
Override the encodeJson and decodeJson methods of WKMessageContent to start encoding and decoding: 
// Encode send content
encodeJson(): Record<string, Object> {
  let json: Record<string, Object> = {};
  json['uid'] = this.uid;
  json['name'] = this.name;
  json['avatar'] = this.avatar;
  return json;
}

// Decode content
decodeJson(jsonStr: string): WKMessageContent {
  let json = CommonUtil.jsonToRecord(jsonStr);
  if (json !== undefined) {
    this.uid = CommonUtil.readString(json, 'uid');
    this.name = CommonUtil.readString(json, 'name');
    this.avatar = CommonUtil.readString(json, 'avatar');
  }
  return this;
}
When encoding and decoding messages, there’s no need to consider the type field, as the SDK handles it internally

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Step 3: Register Message

// Register custom message
WKIM.shared.messageManager().registerMsgContent(16, (jsonStr: string) => {
  return new CardMessageContent().decodeJson(jsonStr);
});

​
Complete Business Card Message Implementation

// Custom regular message
export class CardMessageContent extends WKMessageContent {
  uid: string = '';
  name: string = '';
  avatar: string = '';
  
  constructor() {
    super();
    this.contentType = 16; // Specify type
  }

  // Encode send content
  encodeJson(): Record<string, Object> {
    let json: Record<string, Object> = {};
    json['uid'] = this.uid;
    json['name'] = this.name;
    json['avatar'] = this.avatar;
    return json;
  }

  // Decode content
  decodeJson(jsonStr: string): WKMessageContent {
    let json = CommonUtil.jsonToRecord(jsonStr);
    if (json !== undefined) {
      this.uid = CommonUtil.readString(json, 'uid');
      this.name = CommonUtil.readString(json, 'name');
      this.avatar = CommonUtil.readString(json, 'avatar');
    }
    return this;
  }

  // Recent conversation display content
  displayText(): string {
    return '[Business Card]';
  }
  
  // Validate message content
  isValid(): boolean {
    return this.uid.length > 0 && this.name.length > 0;
  }
}

// Register business card message type
WKIM.shared.messageManager().registerMsgContent(16, (jsonStr: string) => {
  return new CardMessageContent().decodeJson(jsonStr);
});

// Send business card message
function sendCardMessage(channelId: string, channelType: number, uid: string, name: string, avatar: string): void {
  const cardContent = new CardMessageContent();
  cardContent.uid = uid;
  cardContent.name = name;
  cardContent.avatar = avatar;
  
  if (cardContent.isValid()) {
    WKIM.shared.messageManager().send(cardContent, new WKChannel(channelId, channelType));
  }
}

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Custom Attachment Messages

Sometimes we need to send messages with attachments when sending messages. WuKongIM also provides custom attachment messages, which are not much different from regular messages. Below we use location messages as an example.

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Step 1: Define Message

Note that custom attachment messages need to inherit from WKMediaMessageContent instead of WKMessageContent. 
export class LocationMessageContent extends WKMediaMessageContent {
  address: string = '';
  longitude: number = 0.0;
  latitude: number = 0.0;

  constructor() {
    super();
    this.contentType = 17; // Specify type
  }
}
WKMediaMessageContent provides url and localPath fields, so custom messages don’t need to define network address and local address fields again

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Step 2: Encoding and Decoding

We need to send longitude, latitude, address, url information to the recipient. The final message content passed is: 
{
  "type": 17,
  "longitude": 115.25,
  "latitude": 39.26,
  "url": "xxx",
  "address": "xxx"
}
Override the encodeJson and decodeJson methods of WKMessageContent to start encoding and decoding: 
// Encode
encodeJson(): Record<string, Object> {
  let json: Record<string, Object> = {};
  json['url'] = this.url;
  json['longitude'] = this.longitude;
  json['latitude'] = this.latitude;
  json['address'] = this.address;
  return json;
}

// Decode
decodeJson(jsonStr: string): WKMessageContent {
  let json = CommonUtil.jsonToRecord(jsonStr);
  if (json !== undefined) {
    this.address = CommonUtil.readString(json, 'address');
    this.url = CommonUtil.readString(json, 'url');
    this.longitude = CommonUtil.readNumber(json, 'longitude');
    this.latitude = CommonUtil.readNumber(json, 'latitude');
  }
  return this;
}

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Step 3: Register Message

// Register custom message
WKIM.shared.messageManager().registerMsgContent(17, (jsonStr: string) => {
  return new LocationMessageContent().decodeJson(jsonStr);
});

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Message Extensions

As business develops, applications have increasingly more features in chat. To meet most requirements, WuKongIM has added message extension functionality. Message extensions are divided into local extensions and remote extensions. Local extensions are only for local app use and will be lost after uninstalling the app. Remote extensions are saved on the server and data will be restored after uninstalling and reinstalling.

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Local Extensions

Local extensions are the localExtraMap field in the message object WKMsg. 
/**
 * Modify message local extensions
 *
 * @param clientMsgNo Client ID
 * @param extra   Extension fields
 */
WKIM.shared.messageManager().updateLocalExtra(clientMsgNo: string, extra: Record<string, Object>);
After successful update, the SDK will trigger a refresh message callback

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Remote Extensions

Remote extensions are the remoteExtra field in the message object WKMsg. 
WKIM.shared.messageManager().saveRemoteExtras(list: WKMsgExtra[]);
After successful update, the SDK will trigger a refresh message callback

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Message Read/Unread

Message read/unread is also called message receipts. Message receipt functionality can be set through settings. 
let option = new WKSendOptions();
option.setting.receipt = 1; // Enable receipts
// Send message
WKIM.shared.messageManager().sendWithOption(textModel, channel, option);
When a logged-in user views messages sent by others, if the sender has enabled message receipts, the viewed messages need to be uploaded to the server to mark them as read. When the sender or yourself uploads read messages, the business server will send a sync message extension cmd (command) message syncMessageExtra. At this time, you need to sync the latest message extensions and save them to the SDK.

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Message Reply

In chat, if there are too many messages, sending message replies will make the messages very messy and hard to follow. At this time, you need to make specific replies to certain messages, which is message reply. When sending a message, you just need to assign the WKReply object in the message content WKMessageContent to achieve the message reply effect. 
let textModel: WKTextContent = new WKTextContent(this.sendContent);
textModel.reply = new WKReply();
textModel.reply.messageId = '';
// Set other field information

// Send message
WKIM.shared.messageManager().send(textModel, channel);

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WKReply Structure Description

export class WKReply {
  // Root message ID of the replied message, the first reply message ID in multi-level replies
  rootMid = '';
  // Replied message ID
  messageId = '';
  // Replied MessageSeq
  messageSeq = 0;
  // Replied user uid
  fromUID = '';
  // Replied user name
  fromName = '';
  // Replied message string
  contentEdit = '';
  // Edit time
  editAt = 0;
  // Reply message revoke flag 1.yes
  revoke = 0;
  // Replied message edited content
  contentEditMsgModel?: WKMessageContent;
  // Replied message body
  payload?: WKMessageContent;
}

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Message Reactions (Likes)

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Save

WKIM.shared.messageManager().saveReactions(list: WKMsgReaction[]);
The same user can only make one reaction to the same message. Repeated reactions with different emojis to the same message will be treated as modifying the reaction, while repeated reactions with the same emoji will be treated as deleting the reaction
After the SDK updates message reactions, it will trigger a message refresh event. The app needs to listen for this event and refresh the UI. Listen for message reaction refresh: 
// Listen for message reaction refresh
WKIM.shared.messageManager().addRefreshReactionListener((list) => {
  // Refresh UI
});

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Get

WKIM.shared.messageManager().getMsgReactions(messageId: string);

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WKMsgReaction Data Structure Description

export class WKMsgReaction {
  // Message ID
  messageId = "";
  // Channel ID
  channelId = "";
  // Channel type
  channelType = WKChannelType.personal;
  // Reactor uid
  uid = "";
  // Message sequence number
  seq = 0;
  // Reaction emoji
  emoji = "";
  // Is deleted 1.yes
  isDeleted = 0;
  // Creation time
  createdAt = "";
}

​
Complete Advanced Features Manager

class AdvancedFeaturesManager {
  
  static initialize(): void {
    // Register custom messages
    this.registerCustomMessages();
    
    // Setup message extensions
    this.setupMessageExtensions();
    
    // Setup message receipts
    this.setupMessageReceipts();
    
    // Setup message reactions
    this.setupMessageReactions();
    
    console.log('Advanced features manager initialized');
  }
  
  private static registerCustomMessages(): void {
    // Register business card message
    WKIM.shared.messageManager().registerMsgContent(16, (jsonStr: string) => {
      return new CardMessageContent().decodeJson(jsonStr);
    });
    
    // Register location message
    WKIM.shared.messageManager().registerMsgContent(17, (jsonStr: string) => {
      return new LocationMessageContent().decodeJson(jsonStr);
    });
  }
  
  private static setupMessageExtensions(): void {
    // Setup upload message extra callback
    WKIM.shared.config.provider.uploadMessageExtraCallback = (extra: WKMsgExtra) => {
      this.uploadMessageExtra(extra);
    };
  }
  
  private static setupMessageReceipts(): void {
    // Setup message receipt handling
    // This would typically involve listening for receipt-related commands
  }
  
  private static setupMessageReactions(): void {
    // Listen for message reaction refresh
    WKIM.shared.messageManager().addRefreshReactionListener((list) => {
      console.log('Message reactions updated:', list.length);
    });
  }
  
  private static async uploadMessageExtra(extra: WKMsgExtra): Promise<void> {
    try {
      // Upload message extra to business server
      console.log('Uploading message extra:', extra.messageId);
    } catch (error) {
      console.error('Failed to upload message extra:', error);
    }
  }
}

// Initialize advanced features
AdvancedFeaturesManager.initialize();

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Next Steps

Data Source Configuration

Return to data source configuration

Message Management

Return to message handling functionality

Channel Management

Return to channel management functionality

Basic Features

Return to basic features

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Summary

HarmonyOS SDK has now completed all core functionality documentation: ✅ Integration Guide - Complete installation and configuration guidance
✅ Basic Features - Connection management and basic APIs
✅ Message Management - Message sending/receiving and history messages
✅ Channel Management - Channel information and member management
✅ Conversation Management - Conversation lists and unread messages
✅ Data Source Configuration - File upload and data synchronization
✅ Advanced Features - Custom messages and extension features HarmonyOS SDK documentation is now fully complete, providing developers with comprehensive technical guidance from beginner to advanced levels! 🎉