title: How to keep only first added Fragment in back stack (fragment overlapping)?
body: <p>Scenario what i'm trying to achieve:</p>
  
  <ol>
  <li>Loading activity with two frame containers (for list of items and for details).</li>
  <li>At the app launch time add listFragment in listFrame and some initial infoFragment in detailsFrame containers.</li>
  <li>Navigating through list items without adding each detail transaction to back stack (want to keep only infoFragment in stack).</li>
  <li>As soon as user hit back button (navigate back) he falls back to intial infoFragment what was added in launch time.</li>
  <li>If sequential back navigation fallows then apps exit.</li>
  </ol>
  
  <p>My code:</p>
  
  <pre><code>        protected override void OnCreate(Bundle savedInstanceState)
          {
  ...
              var listFrag = new ListFragment();
              var infoFrag = new InfoFragment();
              var trans = FragmentManager.BeginTransaction();
              trans.Add(Resource.Id.listFrame, listFrag);
              trans.Add(Resource.Id.detailsFrame, infoFrag);
              trans.Commit();
  ...
          }
  
          public void OnItemSelected(int id)
          {
              var detailsFrag = DetailFragment.NewInstance(id);
              var trans = FragmentManager.BeginTransaction();
              trans.Replace(Resource.Id.detailsFrame, detailsFrag);
              if (FragmentManager.BackStackEntryCount == 0)
                  {
                      trans.AddToBackStack(null);
                  }
              trans.Commit();
          }
  </code></pre>
  
  <p>My problem:</p>
  
  <p>After back button has been hit, infoFrag is overlapped with previous detailFrag! Why?</p>