MessageListViewModel

Previously, our XML and Compose message list ViewModels used the low level client directly to make API calls and enable user interaction. In order to make our code more reliable and the maintenance of our codebase easier, we introduced a layer of shared code between the two message list ViewModels. That layer is represented by a class called MessageListController.

Using the ViewModelFactory

If you're using our MessageListViewModelFactory, you'll notice that we added new parameters allowing for greater control over the ViewModel's behaviour:

public class MessageListViewModelFactory @JvmOverloads constructor(
    private val cid: String,
    private val messageId: String? = null,
    private val parentMessageId: String? = null,
    private val chatClient: ChatClient = ChatClient.instance(),
    private val clientState: ClientState = chatClient.clientState,
    private val messageLimit: Int = MessageListController.DEFAULT_MESSAGES_LIMIT,
    private val enforceUniqueReactions: Boolean = true,
    private val maxAttachmentCount: Int = AttachmentConstants.MAX_ATTACHMENTS_COUNT,
    private val maxAttachmentSize: Long = AttachmentConstants.MAX_UPLOAD_FILE_SIZE,
    private val showSystemMessages: Boolean = true,
    private val deletedMessageVisibility: DeletedMessageVisibility = DeletedMessageVisibility.ALWAYS_VISIBLE,
    private val messageFooterVisibility: MessageFooterVisibility = MessageFooterVisibility.WithTimeDifference(),
    private val dateSeparatorHandler: DateSeparatorHandler = DateSeparatorHandler.getDefaultDateSeparatorHandler(),
    private val threadDateSeparatorHandler: DateSeparatorHandler =
        DateSeparatorHandler.getDefaultThreadDateSeparatorHandler(),
    private val messagePositionHandler: MessagePositionHandler = MessagePositionHandler.defaultHandler(),
) : ViewModelProvider.Factory {

note

The highlighted parameters have been added and the parameter navigateToThreadViaNotification: Boolean has been removed as navigating to thread messages via push notifications is the default behavior in v6.

• enforceUniqueReactions: Determines if a single user is able to set multiple reactions to a single message.
• maxAttachmentCount: The maximum number of attachments that can be sent in a single message.
• maxAttachmentSize: The maximum size of a single attachment, expressed in bytes. Restricted to 100mb by default by Stream's CDN.
• showSystemMessages: If system messages should be visible.
• deletedMessageVisibility: Sets the visibility of the deleted messages according to user ownership.
• messageFooterVisibility: Sets the visibility of message footers.
• dateSeparatorHandler: Determines the visibility of date separators inside the message list.
• threadDateSeparatorHandler: Determines the visibility of date separators inside the message list when the list is in thread mode.
• messagePositionHandler: Determines the position of the message inside the group.

Parameters showDateSeparators: Boolean and dateSeparatorThresholdMillis: Long have been removed in favor of the new date separator handlers which allow for greater flexibility.

Instantiating the ViewModel

We recommend that you instantiate the model using MessageListViewModelFactory, however if you want to instantiate it yourself, then you'll notice its signature has changed.

Previously, the ViewModel had the following signature:

public class MessageListViewModel(
    private val cid: String,
    private val messageId: String? = null,
    private val chatClient: ChatClient = ChatClient.instance(),
    private val clientState: ClientState = chatClient.clientState,
    private val messageLimit: Int = DEFAULT_MESSAGES_LIMIT,
    private val navigateToThreadViaNotification: Boolean = false,
) : ViewModel()

Currently, the ViewModel holds only two parameters:

public class MessageListViewModel(
   private val messageListController: MessageListController,
   private val chatClient: ChatClient = ChatClient.instance(),
) : ViewModel()

MessageListController

The controller has now been made the driving part behind MessageListViewModel. In turn, this means that the parameters necessary to adjust the functioning of the ViewModel have been moved to the controller:

public class MessageListController(
    private val cid: String,
    private val clipboardHandler: ClipboardHandler,
    private val messageId: String? = null,
    private val parentMessageId: String? = null,
    public val messageLimit: Int = DEFAULT_MESSAGES_LIMIT,
    private val chatClient: ChatClient = ChatClient.instance(),
    private val clientState: ClientState = chatClient.clientState,
    private val deletedMessageVisibility: DeletedMessageVisibility = DeletedMessageVisibility.ALWAYS_VISIBLE,
    private val showSystemMessages: Boolean = true,
    private val messageFooterVisibility: MessageFooterVisibility = MessageFooterVisibility.WithTimeDifference(),
    private val enforceUniqueReactions: Boolean = true,
    private val dateSeparatorHandler: DateSeparatorHandler = DateSeparatorHandler.getDefaultDateSeparatorHandler(),
    private val threadDateSeparatorHandler: DateSeparatorHandler =
        DateSeparatorHandler.getDefaultThreadDateSeparatorHandler(),
    private val messagePositionHandler: MessagePositionHandler = MessagePositionHandler.defaultHandler(),
)

You'll notice that these parameters seem familiar, this is because all of them are passed down to the controller by MessageListViewModelFactory and have been covered in the section addressing the changes made to the ViewModel factory.