Message Classification

IM messages are classified by destination into two types: one-to-one messages (also called C2C messages) and group messages.

IM messages can also be classified by content into text messages, custom (signaling) messages, image messages, video messages, voice messages, file messages, location messages, and group tips.

Sending and Receiving a Simple Message

V2TIMManager provides a set of simple APIs for sending and receiving messages. Although these APIs can be used to send or receive text messages and custom (signaling) messages, they are easy to use and only a few minutes are needed to configure access.

Sending text and signaling messages (simplified APIs)

To send text messages, call sendC2CTextMessage or sendGroupTextMessage. Text messages will be filtered by IM for sensitive words. If a message containing sensitive words is sent, the 80001 error code is returned. To send C2C custom (signaling) messages, call sendC2CCustomMessage or sendGroupCustomMessage. A custom message is essentially a section of the binary buffer, which is often used to transfer custom signaling in your app. Its content is not filtered for sensitive words.

Receiving text and signaling messages (simplified APIs)

To listen to simple text and signaling messages, call addSimpleMsgListener. To listen to complex image, video, and voice messages, call addAdvancedMsgListener defined in V2TIMMessageManager.

Do not use addSimpleMsgListener together with addAdvancedMsgListener as this may produce logic bugs.

Typical example: sending and receiving on-screen comments in a livestreaming group

In the livestreaming scenario, a common way of communicating is to send and receive on-screen comments in a livestreaming group. This can be easily implemented through the simple message APIs.

1. The anchor can call createGroup to create a livestreaming group (AVChatRoom) and record the group ID in the list of rooms in the "Broadcasting" state.
2. A viewer can select an anchor that he/she likes and call joinGroup to join the AVChatRoom created by this anchor.
3. The message sender can call sendGroupTextMessage to send a group text message as an on-screen comment.
4. The message recipients can call addSimpleMsgListener to register a simple message listener and use the listener callback function onRecvGroupTextMessage to obtain text messages.

"FlyHeart" is an instruction. To configure the "FlyHeart" floating heart feature for an AVChatRoom, perform the steps below:

1. Define a custom message type, for example, a JSON string { "command": "favor", "value": 101 }.
2. Call sendGroupCustomMessage to send a message and call onRecvGroupCustomMessage to receive the message.

Sending and Receiving Rich Media Messages

Image, video, voice, file, and location messages are called rich media messages. Compared with simple messages, it is more complex to send or receive rich media messages.

• Before sending a rich media message, use the create function to create a V2TIMMessage object. Then, call the corresponding send API to send this message.
• When receiving the rich media message, check elemType and perform secondary parsing on the Elem obtained based on elemType.

Sending Rich Media Messages

The following takes an image message as an example to describe the process of sending a rich media message.

1. The sender calls createImageMessage to create an image message and obtain the V2TIMMessage message object.
2. The sender calls sendMessage to send the created message object.

Receiving Rich Media Messages

1. The recipient calls addAdvancedMsgListener to set the advanced message listener.
2. The recipient obtains the image message V2TIMMessage through the listener callback onRecvNewMessage.
3. The recipient parses elemType in V2TIMMessage and performs secondary parsing based on the message type to obtain the content of Elem in the message.

Typical example: sending and receiving image messages

The sender creates and sends an image message.

// Create an image message.
V2TIMMessage v2TIMMessage = V2TIMManager.getMessageManager().createImageMessage("/sdcard/test.png");
// Send the image message.
V2TIMManager.getMessageManager().sendMessage(v2TIMMessage, "toUserID", null, V2TIMMessage.V2TIM_PRIORITY_DEFAULT, true, null,  new V2TIMSendCallback<V2TIMMessage>() {
@Override
public void onError(int code, String desc) {
// The image message failed to be sent.
}
@Override
public void onSuccess(V2TIMMessage v2TIMMessage) {
// The image message is successfully sent.
}
@Override
public void onProgress(int progress) {
// Image upload progress (0-100)
}
});

The recipient identifies the image message and parses the message to obtain the original image, large image, and thumbnail contained in the message.

@Override
public void onRecvNewMessage(V2TIMMessage msg) {
int elemType = msg.getElemType();
if (elemType == V2TIMMessage.V2TIM_ELEM_TYPE_IMAGE) {
V2TIMImageElem v2TIMImageElem = msg.getImageElem();
// An image message contains an image in three different sizes: original image, large image, and thumbnail. (The SDK automatically generates the large image and thumbnail.)
- A large image is an image obtained after the original image is proportionally compressed. After the compression, the compressed image has a height and width equal to 720 pixels.
- A thumbnail is an image obtained after the original image is proportionally compressed. After the compression, the compressed image has a height and width equal to 198 pixels.
List<V2TIMImageElem.V2TIMImage> imageList = v2TIMImageElem.getImageList();
for (V2TIMImageElem.V2TIMImage v2TIMImage : imageList) {
String uuid = v2TIMImage.getUUID(); // Image ID
int imageType = v2TIMImage.getType(); // Image type
int size = v2TIMImage.getSize(); // Image size (bytes)
int width = v2TIMImage.getWidth(); // Image width
int height = v2TIMImage.getHeight(); // Image height
// Set the image download path `imagePath`. Here, `uuid` can be used as an identifier to avoid repeated downloads.
String imagePath = "/sdcard/im/image/" + "myUserID" + uuid;
File imageFile = new File(imagePath);
if (imageFile.exists()) {
v2TIMImage.downloadImage(imagePath, new V2TIMDownloadCallback() {
@Override
public void onProgress(V2TIMElem.V2ProgressInfo progressInfo) {
// Image download progress. `v2ProgressInfo.getCurrentSize()` indicates the downloaded size, and `v2ProgressInfo.getTotalSize()` indicates the total file size.
}
@Override
public void onError(int code, String desc) {
// The image failed to be downloaded.
}
@Override
public void onSuccess() {
// The image download is completed.
}
});
} else {
// The image already exists.
}
}  
}
}

For more information on the message parsing sample code, see FAQs -> 5. How can I parse different types of messages?.

Setting Offline Push (offlinePushInfo)

When the recipient's app is killed, the IM SDK cannot receive new messages through the normal network connection. In this scenario, the offline push service provided by the mobile phone manufacturer must be used to notify the recipient of new messages. For more information, see Offline Push (Android).

Setting the title and content for offline push

When sending messages, you can use the offlinePushInfo field in the sendMessage API to set the title and content for offline push.

// Create and send a text message to groupA and customize the title and content for offline push.
V2TIMMessage v2TIMMessage = V2TIMManager.getMessageManager().createTextMessage(content);
V2TIMOfflinePushInfo v2TIMOfflinePushInfo = new V2TIMOfflinePushInfo();
// Set the title of the notification bar.
v2TIMOfflinePushInfo.setTitle("offline_title");
// Set the content of the notification bar.
v2TIMOfflinePushInfo.setDesc("offline_desc");
// Send a message.
V2TIMManager.getMessageManager().sendMessage(v2TIMMessage, null, "groupA", V2TIMMessage.V2TIM_PRIORITY_DEFAULT, false,  v2TIMOfflinePushInfo, new V2TIMSendCallback<V2TIMMessage>() {
@Override
public void onError(int code, String desc) {
// The message failed to be sent.
}
@Override
public void onSuccess(V2TIMMessage v2TIMMessage) {
// The message is sent successfully.
}
@Override
public void onProgress(int progress) {
}
});

Clicking a pushed message to go to the corresponding chat window

To implement this feature, the sender needs to set ext, which is the extended field of the offline push object offlinePushInfo, when sending a message. When the recipient opens the app, the recipient can obtain ext by using one of the different methods provided by different mobile phone vendors for obtaining custom content, and then go to the corresponding chat window based on the content of ext.

The following example assumes that Denny sends a message to Vinson.
Sender: Denny needs to set ext before sending a message.

// Denny sets `offlinePushInfo` and specifies `ext` before sending a message.
JSONObject jsonObject = new JSONObject();
try {
jsonObject.put("action", "jump to denny");
} catch (JSONException e) {
e.printStackTrace();
}
String extContent = jsonObject.toString();
V2TIMOfflinePushInfo v2TIMOfflinePushInfo = new V2TIMOfflinePushInfo();
v2TIMOfflinePushInfo.setExt(extContent.getBytes());

V2TIMManager.getMessageManager().sendMessage(v2TIMMessage, "vinson", null, V2TIMMessage.V2TIM_PRIORITY_DEFAULT, false,  v2TIMOfflinePushInfo, new V2TIMSendCallback<V2TIMMessage>() {
@Override
public void onError(int code, String desc) {}
@Override
public void onSuccess(V2TIMMessage v2TIMMessage) {}
@Override
public void onProgress(int progress) {}
});

Recipient: although Vinson's app is not online, it can still receive the notification message pushed offline by the mobile phone vendor’s offline push method (such as OPPO Push). When Vinson clicks the pushed message, the app is started.

// After starting the app, Vinson obtains the custom content from the opened `Activity`.
Bundle bundle = intent.getExtras();
Set<String> set = bundle.keySet();
if (set != null) {
for (String key : set) {
// `key` and `value` correspond to `extKey` and `ext content` set at the sender side.
String value = bundle.getString(key);
if (value.equals("jump to denny")) {
// Go to the chat window with Denny.
...
}
}
}

Setting onlineUserOnly so that Messages Can Be Received Only Online

In some scenarios, you may wish that sent messages can only be received by online users. In this case, recipients are not aware of the message when they are offline. For this purpose, you can set onlineUserOnly to true when calling sendMessage. When this parameter is set, the sent messages differ from common messages in the following ways:

• Messages cannot be stored offline. That is, the recipient cannot receive messages unless he/she is online.
• Messages do not support multi-device roaming. That is, if the recipient has received a message on one terminal, this message cannot be received on any other terminal no matter whether it has been read or not.
• Messages cannot be stored locally. That is, these messages cannot be retrieved from historical messages that are stored locally or in cloud.

** Typical example: displaying "The other party is typing..."
In a one-to-one chat scenario, you can call sendMessage to send the "I am typing..." message. When the recipient receives this message, "The other party is typing..." is displayed on the UI. The sample code is as follows:

// Sending the "I am typing..." message to userA.
JSONObject jsonObject = new JSONObject();
try {
jsonObject.put("command", "textInput");
} catch (JSONException e) {
e.printStackTrace();
}
V2TIMMessage v2TIMMessage = V2TIMManager.getMessageManager().createCustomMessage(jsonObject.toString().getBytes());
V2TIMManager.getMessageManager().sendMessage(v2TIMMessage, "userA", null, V2TIMMessage.V2TIM_PRIORITY_DEFAULT, true,  v2TIMOfflinePushInfo, new V2TIMSendCallback<V2TIMMessage>() {
@Override
public void onError(int code, String desc) {}
@Override
public void onSuccess(V2TIMMessage v2TIMMessage) {}
@Override
public void onProgress(int progress) {}
});

Recalling Messages

The sender can call the revokeMessage API to recall a successfully sent message. By default, the sender can recall a message that has been sent within 2 minutes. You can change the time limit for message recall. For specific instructions, see Message recall settings。
Message recall requires the support of the UI code at the recipient side. When the sender recalls a message, the recipient will receive a message recall notification, onRecvMessageRevoked. This notification contains the msgID of the recalled message. Based on this msgID, you can identify the message that has been recalled and change the corresponding message bubble to the "Message recalled" state on the UI.

The sender recalls a message

 V2TIMManager.getMessageManager().revokeMessage(v2TIMMessage, new V2TIMCallback() { @Override public void onError(int code, String desc) { // The message failed to be recalled. } @Override public void onSuccess() { // The message is successfully recalled. } });

The recipient learns that the message is recalled

1. Call addAdvancedMsgListener to set the advanced message listener.
2. Call onRecvMessageRevoked to receive the message recall notification.

@Override
public void onRecvMessageRevoked(String msgID) {
// `msgList` is the message list on the current chat window.
for (V2TIMMessage msg : msgList) {
if (msg.getMsgID().equals(msgID)) {
// `msg` is the recalled message. You need to change the corresponding message bubble state on the UI.
}
}
}

Adding Read Receipts for Messages

In the one-to-one chat scenario, when the recipient calls the markC2CMessageAsRead API to mark an incoming message as read, the message sender will receive a read receipt, indicating that the recipient has read his/her message.

Currently, only C2C messages support the read receipt feature, and group messages do not support this feature. Although the markGroupMessageAsRead API is also available to group messages, the group message senders currently cannot receive any read receipts.

The recipient marks messages as read

 // Mark messages coming from Haven as read.  V2TIMManager.getMessageManager().markC2CMessageAsRead("haven", new V2TIMCallback() { @Override public void onError(int code, String desc) { // Messages failed to be marked as read. } @Override public void onSuccess() { // Messages are successfully marked as read. } });

The sender learns that the messages are read

The event notification for message read receipts is located in the advanced message listener V2TIMAdvancedMsgListener. To enable the sender to learn that a message has been read, call addAdvancedMsgListener to set the listener. Then, the sender can receive a read receipt from the recipient through the onRecvC2CReadReceipt callback.

@Override
public void onRecvC2CReadReceipt(List<V2TIMMessageReceipt> receiptList) {
// The recipient may receive multiple read receipts at a time. Therefore, the array callback mode is used here.
for (V2TIMMessageReceipt v2TIMMessageReceipt : receiptList) {
// Message recipient
String userID = v2TIMMessageReceipt.getUserID();
// Time of the read receipt. A message is considered as read if the timestamp in the chat window is not later than `timestamp` here.
long timestamp = v2TIMMessageReceipt.getTimest
}
}

Viewing Historical Messages

You can call getC2CHistoryMessageList to obtain historical messages of one-to-one chats, or call getGroupHistoryMessageList to obtain historical messages of group chats. If the network connection of the current device is normal, the IM SDK pulls historical messages from the server by default. If the network connection is unavailable, the IM SDK directly reads historical messages from the local database.

Pulling historical messages by page

The IM SDK supports pulling historical messages by page. The number of messages pulled per page cannot be too large. Otherwise, the pulling speed will be slow. We recommend that you pull 20 messages per page.
The following example assumes that the historical messages of groupA are pulled by page, and the number of messages per page is 20. The sample code is as follows:

// The value `null` of `lastMsg` is passed in for the first pull, indicating that a total of 20 messages are pulled starting from the most recent message
V2TIMManager.getMessageManager().getGroupHistoryMessageList("groupA", 20, null, new V2TIMValueCallback<List<V2TIMMessage>>() {
@Override
public void onError(int code, String desc) {
// Messages failed to be pulled.
}
@Override
public void onSuccess(List<V2TIMMessage> v2TIMMessages) {
// Messages pulled by page are listed from new to old by default.
if (v2TIMMessages.size() > 0) {
// Obtain the start message for the next pull by page.
V2TIMMessage lastMsg = v2TIMMessages.get(v2TIMMessages.size() - 1);
// Pull the remaining 20 messages.
V2TIMManager.getMessageManager().getGroupHistoryMessageList("groupA", 20, lastMsg, new V2TIMValueCallback<List<V2TIMMessage>>() {
@Override
public void onError(int code, String desc) {
// Messages failed to be pulled.
}

@Override
public void onSuccess(List<V2TIMMessage> v2TIMMessages) {
// Message pulling is completed.
}
});
}
}
});

In actual scenarios, pulling by page is often triggered when the user swipes the interface. Each time the user swipes the message list, pulling by page is triggered once. However, the principle is similar to the preceding sample code. In either case, lastMsg specifies the start message for pulling, and count specifies the number of messages pulled each time.

Precautions

• The storage period of historical messages is as follows:
  • Trial edition: free storage for 7 days, no extension supported.
  • Pro edition: free storage for 7 days, extension supported.
  • Flagship edition: free storage for 30 days, extension supported.
  Extending the storage period of historical messages is a value-added service. You can log in to the IM console to modify the relevant configuration. For more information about billing, see Value-added Service Pricing.
• Only the meeting group (corresponding to the ChatRoom of the earlier version) supports pulling the historical messages of members before members join the group.
• Messages in the AVChatRoom do not support local storage and multi-device roaming. Therefore, the getGroupHistoryMessageList API does not work for AVChatRooms.

Deleting Messages

You can call the deleteMessageFromLocalStorage API to delete received messages locally.

Deleting local messages

V2TIMManager.getMessageManager().deleteMessageFromLocalStorage(v2TIMMessage, new V2TIMCallback() {
@Override
public void onError(int code, String desc) {
// Messages failed to be deleted.
}
@Override
public void onSuccess() {
// Messages are deleted successfully.
}
});

Why are the deleted messages pulled again after the app is uninstalled and then reinstalled?
Currently, IM supports the deletion of local messages only. When the app is reinstalled, as messages still exist in the cloud, historical messages deleted locally can still be pulled from the cloud.

Deleting messages in the cloud

Currently, IM does not support the deletion of messages in the cloud. If messages in the cloud are deleted, a reverse mapping relationship will be set up in the cloud, affecting the overall performance of the system.

Setting Message Permissions

Allowing message sending and receiving only among friends

By default, the IM SDK does not prevent message sending and receiving among strangers. If you want C2C messages to be sent and received only among friends, you can log in to the IM console, choose Feature Configuration -> Login and Messages -> Relationship Check, and enable Check Relationship for One-to-One Messages. After this feature is enabled, you can send messages only to friends. When you try to send messages to strangers, the IM SDK returns the 20009 error code.

Blocking messages from a specified user

If you want to block messages from a specified user, call the addToBlackList API to add this user to the blocklist.
When a user is added to the blocklist, by default, the user does not know that he/she is in the blocklist. That is, after this user sends a message, the prompt still indicates that the message was sent successfully, but in fact, the recipient will not receive the message. If you want a user in the blocklist to know that his/her message failed to be sent, you can log in to the IM console, choose Feature Configuration -> Login and Messages -> Blocklist Check, and disable Show "Sent successfully" After Sending Messages. After this feature is disabled, the IM SDK will return the 20007 error code when a user in the blocklist sends a message.

Blocking messages from a specified group

To block messages from a specified group, you can call the setReceiveMessageOpt API to set the group message receiving option to the V2TIM_GROUP_NOT_RECEIVE_MESSAGE state.

Filtering Sensitive Words

Text messages sent by the IM SDK are filtered by IM for sensitive words. If a sent text message contains sensitive words, the IM SDK will return the 80001 error code.

FAQs

1. Why am I receiving duplicate messages?

Check whether the following logic is correct:

• Check whether addSimpleMsgListener is used together with addAdvancedMsgListener. If yes, when text or custom messages are received, both listeners trigger callback, so duplicate messages are received..
• Check whether the same listener object is added repeatedly. If a listener object is no longer needed, call the corresponding removeSimpleMsgListener or removeAdvancedMsgListener API to remove this listener.

2. Why are deleted messages pulled again after the app is uninstalled and then reinstalled?

Currently, IM supports the deletion of local messages only. When the app is reinstalled, as messages still exist in the cloud, historical messages deleted locally can still be pulled from the cloud.

3. Why do read receipts become invalid after the app is uninstalled and then reinstalled?

In the one-to-one chat scenario, if the recipient calls markC2CMessageAsRead to mark a message as read, the read receipt received by the sender contains timestamp. Based on timestamp, the SDK determines whether the other party has read the message. Currently, timestamp is stored locally, and will be lost when the app is reinstalled.

4. How is a message containing multiple Elem objects parsed?

To reduce the message complexity, 2.0 version APIs no longer support the creation of messages containing multiple Elem objects. If you receive a message containing multiple Elem objects from an earlier version API, perform the steps below:

1. Parse the first Elem object as usual.
2. Use the getNextElem method of the first Elem object to obtain the next Elem object. If the next Elem object exists, the Elem object instance is returned. Otherwise, null is returned.

@Override
public void onRecvNewMessage(V2TIMMessage msg) {
// View the first `Elem` object.
int elemType = msg.getElemType();
if (elemType == V2TIMMessage.V2TIM_ELEM_TYPE_TEXT) {
// Text message
V2TIMTextElem v2TIMTextElem = msg.getTextElem();
String text = v2TIMTextElem.getText();
// Check whether `v2TIMTextElem` is followed by more `Elem` objects.
V2TIMElem elem = v2TIMTextElem.getNextElem();
while (elem != null) {
// Identify the Elem type. Here, `V2TIMCustomElem` is used as an example.
if (elem instanceof V2TIMCustomElem) {
V2TIMCustomElem customElem = (V2TIMCustomElem) elem;
byte[] data = customElem.getData();
}
// Continue to check whether the current `Elem` is followed by more `Elem` objects.
elem.getNextElem();
}
// If `elem` is `null`, all `Elem` objects have been parsed.
}
}

5. How are different types of messages parsed?

Message parsing is a complex process. We provide sample code for parsing different types of messages. You can copy the code to your project and perform secondary development based on your actual needs.