Reaction

Emojis are widely used in real-time chats because they allow users to express their feelings in a direct and vivid way. In Chat, "reactions" allow users to quickly react to a message using emojis in one-to-one chats and chat groups. In group chats, reactions can also be used to cast a vote, for example, by calculating the number of different emojis attached to the message.

The following illustration shows the implementation of adding a reaction to a message, how a conversation looks with reactions, and what retrieving a list of reactions (with related information) looks like.

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This page shows how to use the Chat SDK to implement reactions in your project.

Understand the tech

The SDK provides the following APIs to implement reaction functionalities:

addReaction: Adds a reaction to the specified message.
removeReaction: Removes the reaction from the specified message.
fetchReactionList: Retrieves a list of reactions from the server.
fetchReactionDetail: Retrieves the details of the reaction from the server.

Prerequisites

Before proceeding, ensure that your environment meets the following requirements:

The project integrates a version of the Chat SDK later than v1.0.3 and has implemented the basic real-time chat functionalities.
You understand the API call frequency limit as described in Limitations.

The reaction feature is supported by all types of Pricing Plans and is enabled by default once you have enabled Chat in Agora Console.

Implementation

This section introduces how to implement reaction functionalities in your project.

Add a reaction

Call addReaction to add a reaction to the specified message. In a one-to-one conversation, the peer user receives the onMessageReactionDidChange event. In a group conversation, other group members than the operator receive this event. This event contains the conversation ID, message ID, reaction list of the message, and reaction operation list (reaction ID, user ID of the user that adds the reaction, and the addition operation).

For a reaction, a user can add only once, or the error 1301 is reported for repeated addition.

// reaction: Reaction ID
// msgId: The message ID
// Adds a reaction to the specified message
ChatClient.getInstance()
  .chatManager.addReaction(reaction, msgId)
  .then((result) => {
    console.log("success: ", result);
  })
  .catch((error) => {
    console.log("fail: ", error);
  });
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Remove a reaction

Call removeReaction to remove the specified reaction. In a one-to-one conversation, the peer user receives the onMessageReactionDidChange event. In a group conversation, other group members than the operator receive this event. This event contains the conversation ID, message ID, reaction list of the message, and reaction operation list (ID of the removed reaction, user ID of the user that removes the reaction, and the removal operation).

try {
  await ChatClient.getInstance.chatManager.addReaction(
    messageId: messageId,
    reaction: reaction,
  );
} on ChatError catch (e) {
}
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Retrieve a list of reactions

Call getReactionList to retrieve a list of reactions of messages from the server. This method also returns the basic information of the reactions, including the content of the reaction, the number of users that added or removed the reaction, and a list of the first three user IDs that added or removed the reaction.

try {
  Map<String, List<ChatMessageReaction>> map =
      await ChatClient.getInstance.chatManager.fetchReactionList(
    messageIds: messageIds,
    chatType: ChatType.GroupChat,
    groupId: groupId,
  );
} on ChatError catch (e) {
}
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You can also use the reactionList member in ChatMessage to quickly retrieve the reactions of the specified message.

try {
    List<ChatMessageReaction> reactions = await msg.reactionList();
}on ChatError catch (e) {
}
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Retrieve the details of the reaction

Call fetchReactionDetail to get the detailed information of the reaction from the server. The detailed information includes the reaction content, the number of users that added or removed the reaction, and the complete list of user IDs that added or removed the reaction.

try {
  ChatCursorResult<ChatMessageReaction> result =
      await ChatClient.getInstance.chatManager.fetchReactionDetail(
    messageId: messageId,
    reaction: reaction,
  );
} on ChatError catch (e) {
}
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Listen for reaction status

Use onMessageReactionDidChange to listen for changes or status of the reaction.

    // Adds the chat event handler.
    ChatClient.getInstance.chatManager.addEventHandler(
      "UNIQUE_HANDLER_ID",
      ChatEventHandler(
        onMessageReactionDidChange: (events) {},
      ),
    );

    ...

    // Removes the chat event handler.
    ChatClient.getInstance.chatManager.removeEventHandler("UNIQUE_HANDLER_ID");
}
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