tencent cloud

    // Setting message extension
    V2TimValueCallback<List<V2TimMessageExtensionResult>>
        setMessageExtensionsRes = await TencentImSDKPlugin.v2TIMManager
            .getMessageManager()
            .setMessageExtensions(msgID: '', // ID of the message for extension setting
                extensions: []); // Message extension field
    if (setMessageExtensionsRes.code == 0) {
      // Set message extensions successfully
    }

    // Get message extensions
    V2TimValueCallback<List<V2TimMessageExtension>> getMessageExtensionsRes =
        await TencentImSDKPlugin.v2TIMManager
            .getMessageManager()
            .getMessageExtensions(
              msgID: '', // ID of the message whose extension information is to be obtained
            );
    if (getMessageExtensionsRes.code == 0) {
      // Got message extensions successfully
      getMessageExtensionsRes.data?.forEach((element) {
        element.extensionKey; // Key of the extension field modified
        element.extensionValue; // Value of the extension field modified
      });
    }

    // Delete message extensions
    V2TimValueCallback<List<V2TimMessageExtensionResult>>
        deleteMessageExtensionsRes = await TencentImSDKPlugin.v2TIMManager
            .getMessageManager()
            .deleteMessageExtensions(msgID: '', // ID of the message for extension deletion
                keys: []); // List of keys of the extension fields to be deleted
    if (deleteMessageExtensionsRes.code == 0) {
      // Deleted message extensions successfully
      deleteMessageExtensionsRes.data?.forEach((element) {
        element.extension; // Message extension information
        element.resultCode; // Operation result code
        element.resultInfo; // Result description
      });
    }

    // Create a message listener
    V2TimAdvancedMsgListener listener = V2TimAdvancedMsgListener(
      onRecvMessageExtensionsChanged:
          (String msgID, List<V2TimMessageExtension> extensions) {
        // msgID: ID of the message modified
        // extensions: List of extension fields modified
        for (V2TimMessageExtension element in extensions) {
          element.extensionKey; // Key of the extension field modified
          element.extensionValue; // Value of the extension field modified
        }
      },
      onRecvMessageExtensionsDeleted: (msgID, extensionKeys) {
        // msgID: ID of the message whose extension information is deleted
        // extensionKeys: List of keys whose extension information is deleted
      },
    );
    // Add an event listener for advanced messages
    TencentImSDKPlugin.v2TIMManager
        .getMessageManager()
        .addAdvancedMsgListener(listener: listener);