Thread messages

Threads enable users to create a separate conversation from a specific message within a chat group to keep the main chat uncluttered.

This page shows how to use the Chat SDK to send, receive, recall, and retrieve thread messages in your app.

Understand the tech

The Chat SDK provides the ChatManager, ChatMessage, and ChatThread classes for thread messages, which allows you to implement the following features:

Send a thread message
Receive a thread message
Recall a thread message
Retrieve thread messages

The following figure shows the workflow of how clients send and receive peer-to-peer messages.

Thread Messages

As shown in the figure, the workflow of peer-to-peer messaging is as follows:

Clients retrieve a token from your app server.
Client A and Client B log in to Chat.
Client A sends a message to Client B. The message is sent to the Chat server and the server delivers the message to Client B. When Client B receives the message, the SDK triggers an event. Client B listens for the event and gets the message.

Prerequisites

Before proceeding, ensure that you meet the following requirements:

You have initialized the Chat SDK. For details, see SDK quickstart.
You understand the call frequency limit of the Chat APIs supported by different pricing plans as described in Limitations.

The thread 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 describes how to call the APIs provided by the Chat SDK to implement thread features.

Send a thread message

Sending a thread message is similar to sending a message in a chat group. The difference lies in the isChatThreadMessage field, as shown in the following code sample:

// Calls `createTxtSendMessage` to create a text message. 
// Sets `content` to the content of the text message.
// Sets `chatThreadId` to the thread ID.
ChatMessage message = ChatMessage.createTxtSendMessage(content, chatThreadId); 
// Sets `ChatType` to `GroupChat` as a thread belongs to a chat group.
message.setChatType(ChatType.GroupChat); 
// Sets `isChatThreadMessage` to `true` to mark this message as a thread message.
message.setIsChatThreadMessage(true);
// Calls `setMessageStatusCallback` to listen for the message sending status. You can implement subsequent settings in this callback, for example, displaying a pop-up if the message sending fails.
message.setMessageStatusCallback(new CallBack() {
     @Override
     public void onSuccess() {
        showToast("The message is successfully sent");
     }
     @Override
     public void onError(int code, String error) {
         showToast("Failed to send the message");
     }
     @Override
     public void onProgress(int progress, String status) {
     }
});
// Calls `sendMessage` to send the text message.
ChatClient.getInstance().chatManager().sendMessage(message);

For more information about sending a message, see Send Messages.

Once a thread has a new message, all chat group members receive the ChatThreadChangeListener#onChatThreadUpdated callback. Thread members can also listen for the MessageListener#onMessageReceived callback to receive thread messages, as shown in the following code sample:

MessageListener msgListener = new MessageListener() {
   // The SDK triggers the `onMessageReceived` callback when it receives a message.
   // After receiving this callback, the SDK parses the message and displays it.
   @Override
   public void onMessageReceived(List<ChatMessage> messages) {
       for (ChatMessage message : messages) {
           if(message.isChatThreadMessage()) {
               // You can implement subsequent settings in this callback.
           }
       }
   }
   ...
};
// Calls `addMessageListener` to add a message listener.
ChatClient.getInstance().chatManager().addMessageListener(msgListener);
// Calls `removeMessageListener` to remove the message listener.
ChatClient.getInstance().chatManager().removeMessageListener(msgListener);

For more information about receiving a message, see Receive Messages.

Recall a thread message

For details about how to recall a message, refer to Recall Messages.

Once a message is recalled in a thread, all chat group members receive the ChatThreadChangeListener#onChatThreadUpdated callback. Thread members can also listen for the MessageListener#onMessageRecalled callback, as shown in the following code sample:

MessageListener msgListener = new MessageListener() {
   // The SDK triggers the `onMessageRecalled` callback when it recalls a message.
   // After receiving this callback, the SDK parses the message and updates its display.
   @Override
   public void onMessageRecalled(List<ChatMessage> messages) {
       for (ChatMessage message : messages) {
           if(message.isChatThreadMessage()) {
               // You can implement subsequent settings in this callback.
           }
       }
   }
   ...
};

Retrieve thread messages

You can retrieve thread messages locally or from the server, depending on your production environment.

You can check ChatConversation#isChatThread() to determine whether the current conversation is a thread conversation.

Retrieve messages of a thread from the server

You can call asyncFetchHistoryMessage to retrieve messages of a thread from the server. The only difference between retrieving messages of a thread from the server and retrieving group messages is that a thread ID needs to be passed in for the former and a group ID is required for the latter.

String chatThreadId = "{your chatThreadId}";
Conversation.ConversationType type = Conversation.ConversationType.GroupChat;
int pageSize = 10;
String startMsgId = "";// Starting message ID for retrieving. If you pass in an empty string, the SDK will retrieve messages according to the search direction while ignoring this parameter.
Conversation.SearchDirection direction = Conversation.SearchDirection.DOWN;
ChatClient.getInstance().chatManager().asyncFetchHistoryMessage(chatThreadId, type,
        pageSize, startMsgId, direction, new ValueCallBack<CursorResult<ChatMessage>>() {
    @Override
    public void onSuccess(CursorResult<ChatMessage> value) {
    }
    @Override
    public void onError(int error, String errorMsg) {
    }
});

Retrieve messages of a thread locally

By calling loadAllConversations, you can only retrieve local one-to-one chat conversations and group conversations. To retrieve messages of a thread locally, refer to the following code sample:

// Sets the conversation type to group chat as a thread belongs to a chat group.
// Sets `isChatThread` to `true` to mark the conversation as a thread.
ChatConversation conversation = ChatClient.getInstance().chatManager().getConversation(chatThreadId, ChatConversationType.GroupChat, createIfNotExists, isChatThread);
// Retrieves messages in the specified thread from the local database. The SDK automatically loads and stores the retrieved messages to the memory.
List<ChatMessage> messages = conversation.loadMoreMsgFromDB(startMsgId, pagesize, searchDirection);

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