How is communication and data exchange between the user interface and business logic implemented in the MVVM architecture?

In MVVM architecture (Model-View-ViewModel), the connection between the user interface (View) and business logic (ViewModel) is implemented through a two-way data binding mechanism. This means that changes in the data model are automatically reflected in the interface, and user actions update the data in the ViewModel.

In Android, LiveData or Observable objects are often used for this purpose, which the View subscribes to and reacts to changes. The ViewModel contains the logic and data, while the View only displays and handles user events.

Example with LiveData:

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

// In Activity or Fragment
viewModel.userName.observe(this) { name ->
    textView.text = name
}

// When userName changes in ViewModel, the text in textView will update automatically