The file name.
The file type.
The file URL.
Session type.
The message extension.
The file object.
The sender, which can only be the current user and can not be changed.
The image height.
The message ID.
Whether the message is a thread message.
Whether read receipts are required during a group session.
The key required to download the file.
The thumbnail URL.
The key required to download the thumbnail.
Time.
The recipient.
The message type.
The file URL. If the file is uploaded, you can directly use the URL.
The image width.
The callback for a message sending failure.
The callback of file upload completion.
The callback of a file upload error.
The callback of the file upload progress.
The callback for message sending success.
The message body.