Is it necessary to connect the service layer directly to the user interface?

Direct connection of the service layer to the user interface is generally not recommended. It is better to use an intermediate layer — for example, ViewModel or Presenter, which is responsible for preparing data and interaction logic.

Reasons:

• Separation of concerns: UI is responsible for display, service — for business logic.
• Testability: easier to test business logic separately from UI.
• Maintainability: changes in the service do not directly affect the UI and vice versa.

In Android, the MVVM architectural pattern is often used, where ViewModel connects UI and services, providing data in a form convenient for display.

Example:

class UserViewModel(private val userService: UserService) : ViewModel() {
    val userData = MutableLiveData<User>()

    fun loadUser(userId: String) {
        viewModelScope.launch {
            val user = userService.getUser(userId)
            userData.postValue(user)
        }
    }
}

// In Activity or Fragment, subscribe to userData and update UI