Getting Unresolved Reference from Singleton Class - android-studio

Question

I am working with android studio and in Kotlin. I am working with a Singleton class so my confusion is that my getInstance function is not being called when I am trying to add that into my setupRecyclerView function and it keeps saying it is an unresolved reference. I also have the issue that my NewsListActivity.SimpleItemRecyclerViewAdapter also keeps getting an unresolved reference when I try to reference it. Any help would be greatly appreciated.
package edu.uw.amjadz.material_news
import android.content.Context
import android.graphics.Bitmap
import android.util.LruCache
import com.android.volley.Request
import com.android.volley.RequestQueue
import com.android.volley.toolbox.ImageLoader
import com.android.volley.toolbox.Volley
class Singleton private constructor(context: Context){
private var INSTANCE: edu.uw.amjadz.material_news.Singleton? = null
fun getInstance(context: Context): edu.uw.amjadz.material_news.Singleton {
if(INSTANCE == null){
INSTANCE = Singleton(context)
}
return INSTANCE as edu.uw.amjadz.material_news.Singleton
}
val requestQueue: RequestQueue by lazy {
Volley.newRequestQueue(context.applicationContext)
}
val imageLoader: ImageLoader by lazy {
ImageLoader(requestQueue,
object : ImageLoader.ImageCache{
private val cache = LruCache<String, Bitmap>(20)
override fun getBitmap(url: String?): Bitmap {
return cache.get(url)
}
override fun putBitmap(url: String?, bitmap: Bitmap?) {
cache.put(url, bitmap)
}
}
)
}
fun <T> add(req: Request<T>){
requestQueue.add(req)
}
}
private fun setupRecyclerView(recyclerView: RecyclerView) {
recyclerView.setAdapter(null)
val key = getString(R.string.NEWS_API_KEY)
val url = "https://newsapi.org/v2/everything?q=bitcoin&from=2018-10-01&sortBy=publishedAt&apiKey=$key"
val jsonObjectRequest = JsonObjectRequest(
Request.Method.GET, url, null,
Response.Listener { response ->
recyclerView.adapter = NewsListActivity.SimpleItemRecyclerViewAdapter(this, DummyContent.parseData(response.toString()), twoPane)
},
Response.ErrorListener { error ->
}
)
Singleton.getInstance(this).add(jsonObjectRequest)
if (twoPane){
recyclerView.layoutManager = LinearLayoutManager(this)
} else {
recyclerView.layoutManager = GridLayoutManager(this, 2)
}
}
}
class SimpleItemRecyclerViewAdapter(
private val parentActivity: NewsListActivity,
private val values: List<DummyContent.DummyItem>,
private val twoPane: Boolean
) :
RecyclerView.Adapter<SimpleItemRecyclerViewAdapter.ViewHolder>() {
private val onClickListener: View.OnClickListener
init {
onClickListener = View.OnClickListener { v ->
val item = v.tag as DummyContent.DummyItem
if (twoPane) {
val fragment = NewsDetailFragment().apply {
arguments = Bundle().apply {
putString(NewsDetailFragment.ARG_ITEM_ID, item.id)
}
}
parentActivity.supportFragmentManager
.beginTransaction()
.replace(R.id.news_detail_container, fragment)
.commit()
} else {
val intent = Intent(v.context, NewsDetailActivity::class.java).apply {
putExtra(NewsDetailFragment.ARG_ITEM_ID, item.id)
}
v.context.startActivity(intent)
}
}
}