HomeFragment.kt

class HomeFragment : Fragment() {

    companion object {
        private val TAG = HomeFragment::class.java.name
    }

    private lateinit var binding: FragmentHomeBinding
    private var photosViewModel: PhotosViewModel? = null

    override fun onCreateView(inflater: LayoutInflater,
        container: ViewGroup?,
        savedInstanceState: Bundle?): View? {
        binding = FragmentHomeBindingImpl.inflate(inflater)
        binding.lifecycleOwner = this@HomeFragment
        return binding.root
    }

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        //stuff here
    }

    private fun initBindings() {
        //stuff here
    }

    private fun initViewModels() {
        if (null == photosViewModel) {
            photosViewModel = ViewModelProvider(this@HomeFragment,
                ViewModelFactory(RetrofitService.createService(ApiService::class.java))).get(
                PhotosViewModel::class.java)
            photosViewModel?.loadData()
        }
    }

    private fun initObservers() {
        photosViewModel?.getPhotos()?.observe(viewLifecycleOwner, Observer { result ->
            when (result) {
                is Result.Success -> {
                    EspressoIdlingResource.increment()
                    renderList(result.data)
                    EspressoIdlingResource.decrement()
                    binding.homePhotosProgressContainer.visibility = View.GONE
                    binding.homePhotosList.visibility = View.VISIBLE
                }
                is Result.InProgress -> {
                    binding.homePhotosProgressContainer.visibility = View.VISIBLE
                    binding.homePhotosList.visibility = View.GONE
                }
                is Result.Error -> {
                    binding.homePhotosProgressContainer.visibility = View.GONE
                    Toast.makeText(activity, result.exception.message, Toast.LENGTH_LONG).show()
                }
            }
        })
    }

    private fun fetchMoreData() {
        photosViewModel?.loadDataNextPage()
    }

    private fun renderList(photos: ArrayList<Photo>) {
        if (photos.isNotEmpty()) {
            //when screen starts
            if (photosViewModel?.getCurrentPage() == 1 || binding.homePhotosList.adapter?.itemCount == 0) {
                setRecyclerData(photos)
            } else { //when load more
                if (binding.homePhotosList.adapter == null) { //after load more
                    setRecyclerData(photos)
                    binding.homePhotosList.adapter?.notifyDataSetChanged()
                }
            }
            //load state of rv
            if (photosViewModel?.listState != null) {
                binding.homePhotosList.layoutManager?.onRestoreInstanceState(photosViewModel?.listState)
                photosViewModel?.listState = null
            }
        } else {
            showSnackBarMessage()
        }
    }

    override fun onDestroyView() {
        photosViewModel?.listState = binding.homePhotosList.layoutManager?.onSaveInstanceState()
        super.onDestroyView()
    }
}

ViewModelProviders.of() is deprecated, then updated to ViewModelProvider()