Receiving Message

Feature Description
The RecvNewMsgCallback is used to listen for and receive all types of messages (text, custom, and rich media).
Setting a Message Listener
Adding a listener
The receiver calls the AddRecvNewMsgCallback (Details) to add a message listener. We recommend it be called early, such as after the chat page is initialized, to ensure timely message receiving in the application.
Removing a listener
To stop receiving messages, the receiver can call RemoveRecvNewMsgCallback (Details) to remove the message listener.
Receiving a Text Message
The receiver can receive a one-to-one or group text message by using a message listener in the following steps:
1. Call AddRecvNewMsgCallback to set the event listener.
2. Listen for the RecvNewMsgCallback callback to receive text messages.
3. To stop receiving messages, call RemoveRecvNewMsgCallback to remove the listener. This step is optional and can be performed as needed.
Sample code:
TencentIMSDK.AddRecvNewMsgCallback((List<Message> messages, string user_data)=>{
  foreach(Message message in messages)
  {
    foreach (Elem elem in message.message_elem_array)
    {
      // There is a next element
      if (elem.elem_type == TIMElemType.kTIMElem_Text)
      {
         string text = elem.text_elem_content;
      }
    }
  }
})
Receiving a Custom Message
The receiver can receive a custom one-to-one or group message by using a message listener in the following steps:
1. Call AddRecvNewMsgCallback to set the event listener.
2. Listen for the RecvNewMsgCallback callback to receive custom messages.
3. To stop receiving messages, call RemoveRecvNewMsgCallback to remove the listener. This step is optional and can be performed as needed.
Sample code:
TencentIMSDK.AddRecvNewMsgCallback((List<Message> messages, string user_data)=>{
  foreach(Message message in messages)
  {
    foreach (Elem elem in message.message_elem_array)
    {
      // There is a next element
      if (elem.elem_type == TIMElemType.kTIMElem_Custom)
      {
         string data = elem.custom_elem_data;
         string desc = elem.custom_elem_desc;
         string ext = elem.custom_elem_ext;
      }
    }
  }
})
Receiving a Rich Media Message
The receiver can receive a rich media message by using a message listener in the following steps:
1. Call AddRecvNewMsgCallback to set the event listener.
2. Listen for the RecvNewMsgCallback callback to receive rich media messages.
3. Parse the elem_type attribute in the Message message and then parse the message again according to the type to get the specific content of the elements in the message.
4. To stop receiving messages, call RemoveRecvNewMsgCallback to remove the listener. This step is optional and can be performed as needed.
Image message
The image in an image message can be in three formats: original, large, and thumbnail. The latter two are automatically generated by the SDK during message sending and can be ignored.
Large image: A large image is an image obtained after the original image is proportionally compressed. After the compression, the height or width (whichever is shorter) is equal to 720 pixels.
Thumbnail: A thumbnail is an image obtained after the original image is proportionally compressed. After the compression, the height or width (whichever is shorter) is equal to 198 pixels.
Sample code:
TencentIMSDK.AddRecvNewMsgCallback((List<Message> messages, string user_data)=>{
  foreach(Message message in messages)
  {
    foreach (Elem elem in message.message_elem_array)
    {
      // There is a next element
      if (elem.elem_type == TIMElemType.kTIMElem_Image)
      {
         string path = elem.image_elem_orig_path; // Image upload path. This field applies only to the message sender who can use it to display the image on the screen in advance to optimize the experience.
         switch(elem.image_elem_level)
         {
          case TIMImageLevel.kTIMImageLevel_Orig: // Send the original image
          {
            string id = elem.image_elem_orig_id;
            int h = elem.image_elem_orig_pic_height;
            int w = elem.image_elem_orig_pic_width;
            int size = elem.image_elem_orig_pic_size;
            string url = elem.image_elem_orig_url;
            break;
          }
          case TIMImageLevel.kTIMImageLevel_HD: // Send the large image (large in size)
          {
            string id = elem.image_elem_large_id;
            int h = elem.image_elem_large_pic_height;
            int w = elem.image_elem_large_pic_width;
            int size = elem.image_elem_large_pic_size;
            string url = elem.image_elem_large_url;
            break;
          }
          case TIMImageLevel.kTIMImageLevel_Compression: // Send the thumbnail (small in size; default)
          {
            string id = elem.image_elem_thumb_id;
            int h = elem.image_elem_orig_thumb_height;
            int w = elem.image_elem_orig_thumb_width;
            int size = elem.image_elem_orig_thumb_size;
            string url = elem.image_elem_thumb_url;
            break;
          }
         }
      }
    }
  }
})
Video message
After a video message is received, a video preview is displayed on the chat page, and the video is played back after the user clicks the message.
Two steps are required:
The IM SDK will download video messages when free, which can be directly used by you and will be cleared when the application is uninstalled.
The following sample code demonstrates how to parse the video content from Message:
TencentIMSDK.AddRecvNewMsgCallback((List<Message> messages, string user_data)=>{
  foreach(Message message in messages)
  {
    foreach (Elem elem in message.message_elem_array)
    {
      // There is a next element
      if (elem.elem_type == TIMElemType.kTIMElem_Video)
      {
       // Parse the video message attributes such as thumbnail, playback address, width and height, and size
       string type = elem.video_elem_video_type;
       int size = elem.video_elem_video_size;
       int duration = elem.video_elem_video_duration;
       string path = elem.video_elem_video_path;
       string url = elem.video_elem_video_url;
       int imageType = elem.video_elem_image_type;
       int imageSize = elem.video_elem_image_size;
       int w = elem.video_elem_image_width;
       int h = elem.video_elem_image_height;
       string imagePath = elem.video_elem_image_path;
       string url = elem.video_elem_image_url;
      }
    }
  }
})
Audio message
The IM SDK will download audio messages when free, which can be directly used by you and will be cleared when the application is uninstalled.
The following sample code demonstrates how to parse the audio content from Message:
TencentIMSDK.AddRecvNewMsgCallback((List<Message> messages, string user_data)=>{
  foreach(Message message in messages)
  {
    foreach (Elem elem in message.message_elem_array)
    {
      // There is a next element
      if (elem.elem_type == TIMElemType.kTIMElem_Sound)
      {
       // Parse the audio playback address, local address, size, and duration
       int size = elem.sound_elem_file_size;
       int duration = elem.sound_elem_file_time;
       string path = elem.sound_elem_file_path;
       string url = elem.sound_elem_url;
      }
    }
  }
})
File message
The IM SDK will download file messages when free, which can be directly used by you and will be cleared when the application is uninstalled.
The following sample code demonstrates how to parse the file content from Message:
TencentIMSDK.AddRecvNewMsgCallback((List<Message> messages, string user_data)=>{
  foreach(Message message in messages)
  {
    foreach (Elem elem in message.message_elem_array)
    {
      // There is a next element
      if (elem.elem_type == TIMElemType.kTIMElem_File)
      {
       // Parse the filename, size, URL, etc. of the file message
       int size = elem.file_elem_file_size;
       string path = elem.file_elem_file_path;
       string name = elem.file_elem_file_name;
       string url = elem.file_elem_url;
      }
    }
  }
})
Geographical location message
The following sample code demonstrates how to parse the geographical location content from Message:
TencentIMSDK.AddRecvNewMsgCallback((List<Message> messages, string user_data)=>{
  foreach(Message message in messages)
  {
    foreach (Elem elem in message.message_elem_array)
    {
      // There is a next element
      if (elem.elem_type == TIMElemType.kTIMElem_Location)
      {
       // Parse the geographical location information such as latitude, longitude, and description
       double longitude = elem.location_elem_longitude;
       double latitude = elem.location_elem_latitude;
       string desc = elem.location_elem_desc;
      }
    }
  }
})
Emoji message
The SDK provides a passthrough channel only for emoji messages. Here, index and data can be customized.
For example, the sender can set index to 1 and data to x12345 to indicate the smile emoji.
The receiver parses the received emoji message as 1 and x12345 and displays the message as the smile emoji according to the preset rules.
The following sample code demonstrates how to parse the emoji content from Message:
TencentIMSDK.AddRecvNewMsgCallback((List<Message> messages, string user_data)=>{
  foreach(Message message in messages)
  {
    foreach (Elem elem in message.message_elem_array)
    {
      // There is a next element
      if (elem.elem_type == TIMElemType.kTIMElem_Face)
      {
       string data = elem.face_elem_buf;
       int index = elem.face_elem_index;
      }
    }
  }
})
Group tip message
Group tip messages are tips received by users in addition to ordinary messages in a group chat, for example, "The admin removed alice from the group chat" and "bob renamed the group "xxxx"".
Note: 
 Group tip messages will be received by only group members but not one-to-one chat parties.
There are many types of group tip messages. For more information, see the definition of GroupTipsElem (Details).
After receiving a group tip message, the receiver generally needs to:
1. Parse each field in GroupTipsElem.
2. Identify the message type according to group_tips_elem_tip_type.
3. Merge other fields into the content for display according to the type.
For example:
The receiver parses type as kTIMGroupTip_GroupInfoChange, indicating that this is a notification of group profile change.
The receiver can get the operator information from group_tips_elem_op_user_info and the modified group name from group_tips_elem_group_change_info_array.
At this point, the receiver can merge the "operator" and "modified group name" to create a group tip, such as "Alice renamed the group "group123"".
The following sample code demonstrates how to parse the tip content from V2TIMMessage:
if(tip.group_tips_elem_tip_type == TIMGroupTipType.kTIMGroupTip_GroupInfoChange){
        tip.group_tips_elem_group_id; // Group
        message.group_tips_elem_tip_type; // Group tip type
        message.group_tips_elem_op_user_info; // Operator profile
        message.group_tips_elem_changed_user_info_array; // User profile operated on
        message.group_tips_elem_group_change_info_array; // Group information change details
        message.group_tips_elem_member_change_info_array; // Group member change information
}
Getting the Message Sending Progress
TencentIMSDK.SetMsgElemUploadProgressCallback((Message message, int index, int cur_size, int total_size, string user_data)=>{
    // `message` indicates the message instance being sent.
  // `index` indicates the number of the file being uploaded.
  // `cur_size` indicates the current size (in MB) of the file being uploaded.
  // `total_size` indicates the total size of the file being uploaded.
})
Receiving a Message Containing Multiple Element Objects
1. Use the Message object to parse message_elem_array.
2. Traverse message_elem_array to get all the element objects.
Sample code:
foreach (Elem elem in message.message_elem_array) {
   // There is a next element
}
Feature Description
Setting a Message Listener
- Adding a listener
- Removing a listener
Receiving a Text Message
Receiving a Custom Message
Receiving a Rich Media Message
Getting the Message Sending Progress
Receiving a Message Containing Multiple Element Objects