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The MessageComposer is arguably one of the most important components when building the Chat experience. It allows users to participate in the chat by sending messages and attachments.

There are two versions of the composer that we provide:

  • Bound: This version relies on a ViewModel to set up all of its operations, like sending, editing and replying to a message, as well as handling UI state when the user performs different message actions.
  • Stateless: This is a stateless version of the composer that doesn't know about ViewModels or business logic. It exposes several actions and customization options that let you override the behavior and UI of the component.

The bound version of the composer uses the stateless composer internally. That way, when providing the same state to either component, the behavior will be the same.

Additionally, we cannot provide a default ViewModel, as it requires the channelId to send data, so you'll have to build an instance yourself.

Let's see how to integrate the MessageComposer in your UI.


The easiest way to use the MessageComposer is by combining it with the rest of our components, like so:

fun MyCustomUi() {
modifier = Modifier.fillMaxSize(),
bottomBar = { // 1 - Add the composer as a bottom bar
modifier = Modifier // 2 - customize the component
viewModel = composerViewModel, // 3 - provide ViewModel
// 4 - customize actions
onAttachmentsClick = { attachmentsPickerViewModel.changeAttachmentState(true) },
onCancelAction = {
) {
// 5 - the rest of your UI

Because it doesn't make sense to use the MessageComposer as a standalone component, this example shows how to add it in a Scaffold, with the rest of your UI.

In this example, you took the following steps:

  • Step 1: You set up the MessageComposer as a bottomBar of a Scaffold. This way you dedicate the space on the screen while fitting in the rest of your content.
  • Step 2: You customize the MessageComposer using a set of Modifiers to make it fill the parent width and wrap its height.
  • Step 3: You pass in the ViewModel to bind the composer to. This helps it load all the info it needs to show various states.
  • Step 4: You customize some of the actions of the composer to propagate them to other parts of your business logic.
  • Step 5: You can set up the rest of your UI in the Scaffold body, which can be any of our other components or your custom UI.

Notice how our components allow you to customize the UI to whatever your needs may be as you can combine them with your custom UI or our other components.

You can also customize the behavior of our components to update the rest of your UI state accordingly.

The provided snippet, with the rest of the UI set up using our messages components, will render the following UI.

Default MessageComposer component

Notice how the composer shows the attachments we've selected in the input area, how it shows the label, as well as integrations on the left side and the send button on the right side.

Next, you'll want to handle and customize the actions of the MessageComposer.

Handling Actions#

The composer offers these actions you can customize, as per the signature:

fun MessageComposer(
..., // state and UI
onSendMessage: (Message) -> Unit = { viewModel.sendMessage(it) },
onAttachmentsClick: () -> Unit = {},
onCommandsClick: () -> Unit = {},
onValueChange: (String) -> Unit = { viewModel.setMessageInput(it) },
onAttachmentRemoved: (Attachment) -> Unit = { viewModel.removeSelectedAttachment(it) },
onCancelAction: () -> Unit = { viewModel.dismissMessageActions() },
onMentionSelected: (User) -> Unit = { viewModel.selectMention(it) },
onCommandSelected: (Command) -> Unit = { viewModel.selectCommand(it) },
onAlsoSendToChannelSelected: (Boolean) -> Unit = { viewModel.setAlsoSendToChannel(it) },
  • onSendMessage: Handler when the user taps on the Send button.
  • onAttachmentsClick: Handler when the user taps on the default attachments integration.
  • onCommandsClick: Handler when the user taps on the default commands integration.
  • onValueChange: Handler that exposes text value changes in the composer.
  • onAttachmentRemoved: Handler when the user removes an attachment from selected attachments, in the input area.
  • onCancelAction: Handler when the user cancels the current message action, usually Edit or Reply actions.
  • onMentionSelected: Handler when the user selects a mention.
  • onCommandSelected: Handler when the user selects an instant command.
  • onAlsoSendToChannelSelected: Handler when the user toggles the checkbox for sending messages from thread to channels.

As you can see, most of these actions update the state in the MessageComposerViewModel, or are empty, by default.

To customize these actions, simply pass in a lambda function for each when building your custom UI with our MessageComposer, like in the example above.

Handling Typing Updates#

Typing updates should be sent sparingly as a way of saving valuable API calls. Luckily, we offer such behavior out of the box. MessageComposerViewModel contains MessageComposerController, which in turn uses DefaultTypingUpdatesBuffer in order to intelligently make start and stop typing API calls.

If you want to implement your own buffering mechanism you can pass in an implementation of the TypingUpdatesBuffer interface instead:

// Your custom implementation of TypingUpdatesBuffer


MessageComposer offers the following options for UI customization:

fun MessageComposer(
modifier: Modifier = Modifier,
headerContent: @Composable ColumnScope.(MessageComposerState) -> Unit = { ... },
footerContent: @Composable ColumnScope.(MessageComposerState) -> Unit = { ... },
mentionPopupContent: @Composable (List<User>) -> Unit = { ... },
commandPopupContent: @Composable (List<Command>) -> Unit = { ... },
integrations: @Composable RowScope.(MessageComposerState) -> Unit = { ... },
label: @Composable () -> Unit = { DefaultComposerLabel() },
input: @Composable RowScope.(MessageComposerState) -> Unit = { ... },
trailingContent: @Composable (MessageComposerState) -> Unit = { ... },
  • modifier: Modifier for root component styling. This is useful to set the composer alignment, size, padding and more.
  • headerContent: Slot that's shown as the header. By default MessageInputOptions that show when a message is being edited, or we're replying to another message.
  • footerContent: Slot that's shown as the footer. Present in the Thread mode and allows the user to also send messages from threads to channels.
  • mentionPopupContent: Slot that acts as a popup. By default it shows the MentionSuggestionList when the user starts the mention action.
  • commandPopupContent: Slot that acts as a popup. By default it shows the CommandSuggestionList when the user starts a slash command action.
  • integrations: By default, we show the attachment picker and slash command integrations in our composer. You can override this to support custom integrations.
  • label: Slot that represents the hint, or the label, where there is no user input.
  • input: Slot that represents the core part of the composer, where the user can write new messages. It also displays pending attachments if the user chooses attachments for upload.
  • trailingContent: Slot that represents the send button. The user can tap to send a new message, with or without attachments.

An example of customizing the MessageComposer component is the following:

fun MyCustomComposer() {
modifier = Modifier
viewModel = composerViewModel,
integrations = {},
input = { inputState ->
modifier = Modifier
.padding(start = 8.dp),
messageComposerState = inputState,
onValueChange = { composerViewModel.setMessageInput(it) },
onAttachmentRemoved = { composerViewModel.removeSelectedAttachment(it) },
label = { // create a custom label with an icon
verticalAlignment = Alignment.CenterVertically
) {
imageVector = Icons.Default.Keyboard,
contentDescription = null

modifier = Modifier.padding(start = 4.dp),
text = "Type something",
color = ChatTheme.colors.textLowEmphasis
innerTrailingContent = { // add a send button inside the input
modifier = Modifier
interactionSource = remember { MutableInteractionSource() },
indication = rememberRipple()
) {
val state = composerViewModel.messageComposerState.value

state.inputValue, state.attachments
painter = painterResource(id = R.drawable.stream_compose_ic_send),
tint = ChatTheme.colors.primaryAccent,
contentDescription = null
trailingContent = { Spacer(modifier = Modifier.size(8.dp)) } // remove the outer send button

Notice how you've removed the integrations by passing in an empty composable function, how you override the input parameter to provide a MessageInput that's more suitable to your needs, and how within the input you can customize the label and innerTrailingContent slots. You also replaced the outer trailingContent to remove the send button.

This snippet will provide the following UI. It was really easy to customize this and there are many things you can do with the MessageComposer to make it fit your design needs!

Custom MessageComposer component

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