Message Introduction
The IMLib SDK defines the Message class for message transmission and management.
Message Model
The Message class encapsulates the following key data:
- Attributes for message transmission: Sender ID, Receiver ID, Conversation Type, etc.
- Message Content: Encapsulates the specific content carried by a message, divided into regular message content and media message content. For example, text message content (TextMessage) belongs to regular message content, while image message content (ImageMessage) belongs to media message content. The type of message content, often referred to as the "message type," determines whether to use the interface for sending regular messages or media messages.
The term "message" in the documentation, such as text message, voice message, etc., sometimes refers to the specific content of the message inherited from MessageContent or MediaMessageContent.
The table below describes the key attributes of the Message class. For a complete list of attributes, refer to the API documentation.
| Attribute Name | Type | Description |
|---|---|---|
| ObjectName | String | The identifier for the message type, determined by the value in the io.rong.imlib.MessageTag annotation within the message content. |
| Content | MessageContent | The specific content carried by the message, which must be a subclass object of MessageContent or MediaMessageContent, encapsulating the specific data fields of different message types. The IM service provides predefined message types and specifies a cross-platform consistent message content structure (see Message Type Overview), such as text, voice, image, GIF, etc. You can also create custom message types by customizing the message content. |
| ConversationType | ConversationType | The conversation type enumeration, such as one-to-one chat, group chat, chatroom, ultra group, system conversation, etc. Refer to Conversation Introduction. |
| SenderUserId | String | The user ID of the message sender. |
| TargetId | String | The conversation ID (or target ID), used to identify the other end of the conversation.
|
| ChannelId | String | The ultra group channel ID. |
| MessageId | int | The message ID, which is the unique ID of the message in local storage (database index unique value). |
| UId | String | The message UID, which is globally unique under the same App Key. Only successfully sent messages have a unique ID. |
| MessageDirection | MessageDirection | The message direction enumeration, divided into sending and receiving. |
| SentTime | long | The message sending time. The sending time is the local time of the server when the message reaches the server from the sending client. Uses UNIX timestamp in milliseconds. |
| ReceivedTime | long | The message receiving time. The receiving time is the local time of the client when the message reaches the receiving client. Uses UNIX timestamp in milliseconds. |
| SentStatus | SentStatus | The status of the sent message, such as sending, sent, failed, canceled. |
| ReceivedStatus | ReceivedStatus | The status of the received message, such as whether it has been read or downloaded. For details, see Message Receiving Status. |
| ReadReceiptInfo | ReadReceiptInfo | The read receipt information for group chat messages. For details, refer to Group Chat Message Receipt. |
| isCanIncludeExpansion | boolean | Whether message expansion is allowed. For details, refer to Message Expansion. |
| Expansion | Map<String, String> | The message expansion information. For details, refer to Message Expansion. |
| Extra | String | The additional information of the message, which is a local operation field and will not be sent to the server. Note the difference from MessageContent.extra, which is sent to the other end along with the message. |
| isOffline | boolean | Whether the message is an offline message. This is only valid in the callback method for receiving messages. If the message is an offline message, this value is true; otherwise, it is false. This attribute is supported starting from SDK version 5.4.4. |
| disableUpdateLastMessage | boolean | Whether to disable updating the last message in the conversation. Default is false: update; true: do not update. This attribute is supported starting from SDK version 5.12.2. |
MessageContent
The Message class encapsulates the content attribute, which represents the specific content carried by a message. The type of message content must inherit from the following base classes:
- MessageContent - Regular message content. For example, the text message content (TextMessage) in the SDK's built-in message types inherits from
MessageContent. - MediaMessageContent - Media message content, which inherits from the
MessageContentbase class and adds logic for handling media files. For example, the image message content (ImageMessage) in the SDK's built-in message types inherits fromMediaMessageContent. When sending and receiving messages, the SDK determines whether the message type is a media type. If it is, the upload or download process for media files is triggered.
The IM service provides predefined, cross-platform consistent message content structures (see Message Type Overview), such as text, voice, image, GIF, etc. If you need to implement custom messages, you can inherit from MessageContent or MediaMessageContent to create custom message content.
Message Storage Strategy
The client SDK and IM server identify the type of message, its storage strategy on the local and server sides, and whether it counts towards unread messages through the message annotation (MessageTag). MessageTag is a Java annotation implemented to annotate message content classes. Message-specific content inherited from MessageContent or MediaMessageContent must carry the MessageTag annotation.
If you send messages of the SDK's built-in message types, the MessageTag is automatically added by default, and no additional action is required.
If you need to create custom message types, you need to learn how to correctly create message annotations. For details, see the following documentation: