title: findFirstVisibleItemPosition() always returned -1
body: <p>I try to find that is my first item in <code>recyclerview</code> showed or no.
  I use <code>findFirstVisibleItemPosition()</code> but it is always returned -1 when I scrolled <code>recyclerview</code>.
  I use <code>recyclerview</code> inside <code>viewpager</code>.</p>
  <pre><code>val linearLayoutManager =
          LinearLayoutManager(container.context, LinearLayoutManager.VERTICAL, false)
      recCafeList = binding.recCafeList
  
      recCafeList.layoutManager = linearLayoutManager
      recCafeList.adapter = mAdapter
  
      val po = linearLayoutManager.findFirstVisibleItemPosition()
      val po2 = linearLayoutManager.findFirstCompletelyVisibleItemPosition()
  
      recCafeList.setOnScrollListener(object : RecyclerView.OnScrollListener() {
          
          override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
              super.onScrolled(recyclerView, dx, dy)
              Log.i(&quot;scrollListener&quot;, &quot;$po //// $po2&quot;)
          }
  
      })
  </code></pre>
  <p>Logcat:</p>
  <pre><code>I/scrollListener: -1 //// -1
  I/scrollListener: -1 //// -1
  I/scrollListener: -1 //// -1
  I/scrollListener: -1 //// -1
  I/scrollListener: -1 //// -1
  I/scrollListener: -1 //// -1
  I/scrollListener: -1 //// -1
  I/scrollListener: -1 //// -1
  I/scrollListener: -1 //// -1
  I/scrollListener: -1 //// -1
  I/scrollListener: -1 //// -1
  I/scrollListener: -1 //// -1
  I/scrollListener: -1 //// -1
  </code></pre>