Send and receive messages

After logging in to Chat, users can send the following types of messages to a peer user, a chat group, or a chat room:

Text messages, including hyperlinks and emojis.
Attachment messages, including image, voice, video, and file messages.
Location messages.
CMD messages.
Extended messages.
Custom messages.

The Chat message feature is language agnostic. End users can send messages in any language, as long as their devices support input in that language.

This page shows how to implement sending and receiving these messages using the Chat SDK.

Understand the tech

The Chat SDK uses the ChatManager class to send, receive, and withdraw messages.

The process of sending and receiving a message is as follows:

The message sender creates a text, file, or attachment message using the corresponding create method.
The message sender calls sendMessage to send the message.
The message recipient calls addMessageListener to listens for message events and receives the message in the OnMessageReceived callback.

Prerequisites

Before proceeding, ensure that you meet the following requirements:

You have integrated the Chat SDK, initialized the SDK and implemented the functionality of registering accounts and login. For details, see Chat SDK quickstart.
You understand the API call frequency limits as described in Limitations.

Implementation

This section shows how to implement sending and receiving the various types of messages.

Send a text message

Use the ChatMessage class to create a text message, and send the message.

// Call createTextSendMessage to create a text message. Set content as the content of the text message, and toChatUsernames the user ID of the message recipient.
ChatMessage message = ChatMessage.createTxtSendMessage(content, toChatUsername); 
// Set the message type using the MessageType attribute in Message.
// You can set `MessageType` as `Chat`, `Group`, or `Room`, which indicates whether to send the message to a peer user, a chat group, or a chat room.  
message.setChatType(ChatType.GroupChat); 
 // Send the message
 ChatClient.getInstance().chatManager().sendMessage(message);

// Calls setMessageStatusCallback to set the callback instance to get the status of messaging sending. You can update the status of messages in this callback, for example, adding a tip when the message sending fails.
 message.setMessageStatusCallback(new CallBack() {
     @Override
     public void onSuccess() {
         showToast("Message sending succeeds");
          dialog.dismiss();
     }
     @Override
     public void onError(int code, String error) {
         showToast("Message sending fails");
     }
 });
 ChatClient.getInstance().chatManager().sendMessage(message);

In high-concurrency scenarios, you can set a certain message type or messages from a chat room member as high, normal, or low priority. In this case, low-priority messages are dropped first to reserve resources for the high-priority ones, for example, gifts and announcements, when the server is overloaded. This ensures that the high-priority messages can be dealt with first when loads of messages are being sent in high concurrency or high frequency. Note that this feature can increase the delivery reliability of high-priority messages, but cannot guarantee the deliveries. Even high-priorities messages can be dropped when the server load goes too high.

You can set the priority for all types of messages in the chat room.

ChatMessage message = ChatMessage.createTextSendMessage(content, toChatUsername);
message.setChatType(ChatMessage.ChatType.ChatRoom);
// Set the message priority. The default value is `Normal`, indicating the normal priority.
message.setPriority(ChatMessage.ChatRoomMessagePriority.PriorityHigh);
sendMessage(message);

Receive a message

You can use MessageListener to listen for message events. You can add multiple MessageListeners to listen for multiple events. When you no longer listen for an event, ensure that you remove the listener.

When a message arrives, the recipient receives an onMessgesReceived callback. Each callback contains one or more messages. You can traverse the message list, and parse and render these messages in this callback.

ChatClient.getInstance().chatManager().addMessageListener(msgListener);
MessageListener msgListener = new MessageListener() {
// Traverse the message list, and parse and render the messages.
@Override
public void onMessageReceived(List<ChatMessage> messages) {
}
};
ChatClient.getInstance().chatManager().removeMessageListener(msgListener);

Recall a message

Two minutes after a user sends a message, this user can withdraw it. Contact support@agora.io if you want to adjust the time limit.

try {
    ChatClient.getInstance().chatManager().recallMessage(message);
    EMLog.d("TAG", "Recalling message succeeds");
} catch (ChatException e) {
    e.printStackTrace();
    EMLog.e("TAG", "Recalling message fails: "+e.getDescription());
}

You can also use onMessageRecalled to listen for the message recall state:

/**
 * Occurs when a received message is recalled.
 */
void onMessageRecalled(List<ChatMessage> messages);

Send and receive an attachment message

Voice, image, video, and file messages are essentially attachment messages. This section introduces how to send these types of messages.

Send and receive a voice message

Before sending a voice message, you should implement audio recording on the app level, which provides the URI and duration of the recorded audio file.

Refer to the following code example to create and send a voice message:

// Set voiceUri as the local URI of the audio file, and duration as the length of the file in seconds.
ChatMessage message = ChatMessage.createVoiceSendMessage(voiceUri, duration, toChatUsername);
// Sets the chat type as one-to-one chat, group chat, or chatroom.
if (chatType == CHATTYPE_GROUP)
    message.setChatType(ChatType.GroupChat);
ChatClient.getInstance().chatManager().sendMessage(message);

When the recipient receives the message, refer to the following code example to get the audio file:

VoiceMessageBody voiceBody = (VoiceMessageBody) msg.getBody();
// Retrieves the URL of the audio file on the server.
String voiceRemoteUrl = voiceBody.getRemoteUrl();
// Retrieves the URI if the audio file on the local device.
Uri voiceLocalUri = voiceBody.getLocalUri();

Send and receive an image message

By default, the SDK compresses the image file before sending it. To send the original file, you can set original as true.

Refer to the following code example to create and send an image message:

// Set imageUri as the URI of the image file on the local device. false means not to send the original image. The SDK compresses image files that exceeds 100K before sending them.
ChatMessage.createImageSendMessage(imageUri, false, toChatUsername);
// Sets the chat type as one-to-one chat, group chat, or chatroom.
if (chatType == CHATTYPE_GROUP)
    message.setChatType(ChatType.GroupChat);
ChatClient.getInstance().chatManager().sendMessage(message);

When the recipient receives the message, refer to the following code example to get the thumbnail and attachment file of the image message:

// Retrieves the thumbnail and attachment of the image file.
ImageMessageBody imgBody = (ImageMessageBody) message.getBody();
// Retrieves the image file the server.
String imgRemoteUrl = imgBody.getRemoteUrl();
// Retrieves the image thumbnail from the server.
String thumbnailUrl = imgBody.getThumbnailUrl();
// Retrives the URI of the image file on the local device.
Uri imgLocalUri = imgBody.getLocalUri();
// Retrieves the URI of the image thumbnail on the local device.
Uri thumbnailLocalUri = imgBody.thumbnailLocalUri();

If ChatClient.getInstance().getOptions().getAutodownloadThumbnail() is set as true on the recipient's client, the SDK automatically downloads the thumbnail after receiving the message. If not, you need to call ChatClient.getInstance().chatManager().downloadThumbnail(message) to download the thumbnail and get the path from the thumbnailLocalUri member in messageBody.

Send and receive a video message

Before sending a video message, you should implement video capturing on the app level, which provides the duration of the captured video file.

Refer to the following code example to create and send a video message:

String thumbPath = getThumbPath(videoUri);
ChatMessage message = ChatMessage.createVideoSendMessage(videoUri, thumbPath, videoLength, toChatUsername);
sendMessage(message);

By default, when the recipient receives the message, the SDK downloads the thumbnail of the video message.

If you do not want the SDK to automatically download the video thumbnail, set ChatClient.getInstance().getOptions().setAutodownloadThumbnail as false, and to download the thumbnail, you need to call ChatClient.getInstance().chatManager().downloadThumbnail(message), and get the path of the thumbnail from the thumbnailLocalUri member in messageBody.

To download the actual video file, call SChatClient.getInstance().chatManager().downloadAttachment(message), and get the path of the video file from the getLocalUri member in messageBody.

// If you received a message with video attachment, you need download the attachment before you open it.
if (message.getType() == ChatMessage.Type.VIDEO) {
  VideoMessageBody messageBody = (VideoMessageBody)message.getBody();
  // Get the URL of the video on the server.
  String videoRemoteUrl = messageBody.getRemoteUrl();
  // Download the video.
  ChatClient.getInstance().chatManager().downloadAttachment(message);
      // Set Callback to know whether the download is finished.
  		public void onError(final int error, String message) {
			EMLog.e(TAG, "offline file transfer error:" + message);
			runOnUiThread(new Runnable() {
				@Override
				public void run() {
					if (EaseShowBigImageActivity.this.isFinishing() || EaseShowBigImageActivity.this.isDestroyed()) {
					    return;
					}
                    image.setImageResource(default_res);
                    pd.dismiss();
                    if (error == Error.FILE_NOT_FOUND) {
						Toast.makeText(getApplicationContext(), R.string.Image_expired, Toast.LENGTH_SHORT).show();
					}
				}
			});
		}
		public void onProgress(final int progress, String status) {
			EMLog.d(TAG, "Progress: " + progress);
			final String str2 = getResources().getString(R.string.Download_the_pictures_new);
			runOnUiThread(new Runnable() {
				@Override
				public void run() {
                    if (EaseShowBigImageActivity.this.isFinishing() || EaseShowBigImageActivity.this.isDestroyed()) {
                        return;
                    }
					pd.setMessage(str2 + progress + "%");
				}
			});
		}
	};
	msg.setMessageStatusCallback(callback);
	ChatClient.getInstance().chatManager().downloadAttachment(msg);
  // After the download finishes, get the URI of the local file.
  Uri videoLocalUri = messageBody.getLocalUri();
}

Send and receive a file message

Refer to the following code example to create, send, and receive a file message:

// Set fileLocalUri as the URI of the file message on the local device.
ChatMessage message = ChatMessage.createFileSendMessage(fileLocalUri, toChatUsername);
// Sets the chat type as one-to-one chat, group chat, or chatroom.
if (chatType == CHATTYPE_GROUP)    message.setChatType(ChatType.GroupChat);ChatClient.getInstance().chatManager().sendMessage(message);

While sending a file message, refer to the following sample code to get the progress for uploading the attachment file:

// Calls setMessageStatusCallback to set the callback instance to listen for the state of messaging sending. You can update the message states in this callback.
message.setMessageStatusCallback(new CallBack() {
    @Override
    public void onSuccess() {
        showToast("Message sending succeeds");
        dialog.dismiss();
    }
    @Override
    public void onError(int code, String error) {
        showToast("Message sending fails");
    }
    // The status of sending the message. This only applies to sending attachment files.
    @Override
    public void onProgress(int progress, String status) {
    }
});
ChatClient.getInstance().chatManager().sendMessage(message);

When the recipient receives the message, refer to the following code example to get the attachment file:

NormalFileMessageBody fileMessageBody = (NormalFileMessageBody) message.getBody();
// Retrieves the file from the server.
String fileRemoteUrl = fileMessageBody.getRemoteUrl();
// Retrieves the file from the local device.
Uri fileLocalUri = fileMessageBody.getLocalUri();

Send a location message

To send and receive a location message, you need to integrate a third-party map service provider. When sending a location message, you get the longitude and latitude information of the location from the map service provider; when receiving a location message, you extract the received longitude and latitude information and displays the location on the third-party map.

// Sets the latitude and longitude information of the address.
ChatMessage message = ChatMessage.createLocationSendMessage(latitude, longitude, locationAddress, toChatUsername);
// Sets the chat type as one-to-one chat, group chat, or chatroom.
if (chatType == CHATTYPE_GROUP)    message.setChatType(ChatType.GroupChat);ChatClient.getInstance().chatManager().sendMessage(message);

Send and receive a CMD message

CMD messages are command messages that instruct a specified user to take a certain action. The recipient deals with the command messages themselves.

CMD messages are not stored in the local database.
Actions beginning with em_ and easemob:: are internal fields. Do not use them.

ChatMessage cmdMsg = ChatMessage.createSendMessage(ChatMessage.Type.CMD);
// Sets the chat type as one-to-one chat, group chat, or chat room
cmdMsg.setChatType(ChatType.GroupChat)String action="action1";
// You can customize the action
CmdMessageBody cmdBody = new CmdMessageBody(action);String toUsername = "test1";
// Specify a username to send the cmd message.
cmdMsg.setTo(toUsername);cmdMsg.addBody(cmdBody); ChatClient.getInstance().chatManager().sendMessage(cmdMsg);

To notify the recipient that a CMD message is received, use a seperate delegate so that users can deal with the message differently.

MessageListener msgListener = new MessageListener()
{
  // Occurs when the message is received
  @Override
  public void onMessageReceived(List<ChatMessage> messages) {
  }
  // Occues when a CMD message is received
  @Override
  public void onCmdMessageReceived(List<ChatMessage> messages) {
  }
}

Send a customized message

Custom messages are self-defined key-value pairs that include the message type and the message content.

The following code example shows how to create and send a customized message:

ChatMessage customMessage = ChatMessage.createSendMessage(ChatMessage.Type.CUSTOM);
// Set event as the customized message type, for example, gift.
event = "gift"CustomMessageBody customBody = new CustomMessageBody(event);
// The data type of params is Map<String, String>.
customBody.setParams(params);customMessage.addBody(customBody);
// Specifies the user ID to receive the message, as Chat ID, chat group ID, or chat room ID.
customMessage.setTo(to);
// Sets the chat type as one-to-one chat, group chat, or chat room
customMessage.setChatType(chatType);ChatClient.getInstance().chatManager().sendMessage(customMessage);

Use message extensions

If the message types listed above do not meet your requirements, you can use message extensions to add attributes to the message. This can be applied in more complicated messaging scenarios.

ChatMessage message = ChatMessage.createTxtSendMessage(content, toChatUsername);
// Adds message attributes.
message.setAttribute("attribute1", "value");message.setAttribute("attribute2", true);
// Sends the message
ChatClient.getInstance().chatManager().sendMessage(message);
// Retrieves the message attributes when receiving the message.
message.getStringAttribute("attribute1",null);message.getBooleanAttribute("attribute2", false)

Next steps

After implementing sending and receiving messages, you can refer to the following documents to add more messaging functionalities to your app:

Manage local messages