load state listener for paging

loadstatelistener.kt

/*
 * Progress Updater
 * */
adapter.addLoadStateListener { loadState ->

    if (loadState.refresh is LoadState.Loading ||
        loadState.append is LoadState.Loading)
        // Show ProgressBar
    else {
        // Hide ProgressBar

        // If we have an error, show a toast
        val errorState = when {
            loadState.append is LoadState.Error -> loadState.append as LoadState.Error
            loadState.prepend is LoadState.Error ->  loadState.prepend as LoadState.Error
            loadState.refresh is LoadState.Error -> loadState.refresh as LoadState.Error
            else -> null
        }
        errorState?.let {
            Toast.makeText(this, it.error.toString(), Toast.LENGTH_LONG).show()
        }

    }
}