LiveStreamActivity.kt

class LiveStreamActivity : AppCompatActivity(R.layout.activity_main) {
    private val adapter = MessagesListAdapter()

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        loadMockVideoStream()
        messagesList.adapter = adapter

        val viewModel: LiveStreamViewModel by viewModels()

        sendMessageButton.setOnClickListener {
            viewModel.sendButtonClicked(messageInput.text.toString())
            messageInput.setText("")
            messageInput.clearFocus()
            messageInput.hideKeyboard()
        }
    }

    private fun updateMessagesList(messages: List<Message>) {
        adapter.submitList(messages)
        adapter.notifyDataSetChanged()
        val scrollTarget = adapter.itemCount
        messagesList.scrollToPosition(scrollTarget)
    }
    
    ...
  }