Is it possible to use ViewModel to make changes to the display of an interface element?

The ViewModel in MVVM (Model-View-ViewModel) architecture is designed to represent data and logic related to the display, but not for directly modifying interface elements.

The ViewModel contains properties and commands that are bound to the View (for example, through Data Binding). Changes in the ViewModel are automatically reflected in the interface, but the ViewModel itself should not directly modify UI elements.

If you need to change the appearance or behavior of a UI element, this is usually done in the View (Activity, Fragment, View classes) or through data binding and observers in the ViewModel.

Thus, the ViewModel serves to manage state and data, not to directly change the UI. This helps separate logic from presentation and makes testing easier.

Example:

class UserViewModel : ViewModel() {
    val userName = MutableLiveData<String>()

    fun updateName(newName: String) {
        userName.value = newName
    }
}

In Activity or Fragment:

viewModel.userName.observe(this) { name ->
    textView.text = name // UI change happens here
}