Should ViewBinding properties in fragments always have a backing non-nullable property?

Question

I've been reading https://developer.android.com/topic/libraries/view-binding and was thinking about how they define their view binding property in a fragment.

This is the sample code:

private var _binding: ResultProfileBinding? = null
// This property is only valid between onCreateView and
// onDestroyView.
private val binding get() = _binding!!

override fun onCreateView(
    inflater: LayoutInflater,
    container: ViewGroup?,
    savedInstanceState: Bundle?
): View? {
    _binding = ResultProfileBinding.inflate(inflater, container, false)
    val view = binding.root
    return view
}

override fun onDestroyView() {
    super.onDestroyView()
    _binding = null
}

So _binding is a nullable because the reference to the view will be destroyed in onDestroyView(). However, they use binding as a backing property, which retrieves _binding and makes it non-nullable (whatever the equivalent to force unwrapping is called in Kotlin).

The question is why should we have _binding and binding and which one should be used? It feels like if you are trying to make _binding nullable, then why make it essentially non-nullable with binding and risk accessing the view when it's destroyed?

Answer 1

_binding is nullable so that it can be set to null in onDestroyView, avoiding any memory leaks. but if you tried to access views using _binding then you will have to write _binding!!.someView every time you access any view, use of non-null assertion(!!) quickly becomes redundant and verbose.

So to remove this redundancy there is non-nullable binding. Now you can access your views as binding.someView, no need to use non-null assertion (!!). This can not cause any issue, since views should only be accessed between onCreateView and onDestroyView.