MessageCollection instance allows you to swiftly create a chat view that includes all data. This page explains how to make a view using the collection.
First, create a
MessageCollection instance through the
createMessageCollection() method. Here, you need to set the message filter to determine the message order and the starting point of the message list in the chat view.
startingPoint parameter is the reference point of message retrieval for a chat view. This should be specified as a timestamp.
If you set the value of
startingPoint to the current time or
Long.MAX_VALUE, messages in the view are retrieved in reverse chronological order, showing messages from the newest to the oldest. If you set the value of
startingPoint to the message last read by the current user, messages in the view are fetched in chronological order, starting from the last message seen by the user to the latest message in the channel.
limit sets the number of the messages to retrieve before and after
startingPoint. For example, if the
limit value is set to 100, 50 messages that were sent before
startingPoint and 50 messages after
startingPoint are retrieved, along with the messages that were sent at the exact
startingPoint. Thus a
MessageCollection instance can have more messages than the number set in
After initializing a
MessageCollection instance through the
initialize() method, you need to set
MessageCollectionInitPolicy determines how initialization deals with the message data retrieved from the local cache and API calls. Because we only support
CACHE_AND_REPLACE_BY_API as of now, messages in the local cache must be cleared prior to adding the messages from the Sendbird server.
Retrieves cached messages from the local cache and then replaces them with the messages pulled from the Sendbird server through API calls.
loadNext() methods to retrieve messages from the previous page and the next page.
loadPrevious() method is called, the Chat SDK first checks whether there're more messages to load from the previous page through the
hasPrevious function. The same goes for the
These methods have to be called during initialization as well.
MessageCollectionEventHandler to determine how the client app reacts to message-related events.
The following table shows possible cases where each event handler can be called.
- A new message is created as a real-time event.
- A message is deleted as a real-time event.
- A message is updated as a real-time event.
- The channel information that is included in the user's current chat view is updated as a real-time event.
- The current channel is deleted as a real-time event.
- A huge gap is detected through background sync. In this case, you need to dispose of the view and create a new
In local caching, a gap refers to a chunk of objects that are created and logged on the Sendbird server but missing from the local cache. Depending on the connection status, the client app could miss message events and new messages stored in the Sendbird server may not reach the Chat SDK in the client app. In such cases, a gap is created.
Small gaps can be filled in through changelog sync. However, if the client app has been disconnected for a while, too big of a gap can be created.
A gap can be created for many reasons, such as when a user has been offline for days. When the user opens the app and is online again, the Chat SDK checks with the Sendbird server to see if there are any new messages. If it detects that more than 300 messages are missing from the local cache compared to the Sendbird server, the Chat SDK determines that there is a huge gap and
onHugeGapDetected is called. In this case, the existing
MessageCollection instance should be cleared through the
dispose() method and a new one must be created for better performance.
Note: To adjust the number of missing messages that result in a call for
onHugeGapDetected, contact our support team.
Dispose of the collection
dispose() method should be called when you need to clear the current chat view. For example, this can be used when the current user leaves the channel or when a new collection has to be created due to a huge gap detected by