title: loadInitial method not getting called in PositionalDataSource<Item>
body: <p>I'm implementing PositionalDataSource from Paging Library in Java and getting an issue that constructor of PositionalDataSource's child class is getting called but after that loadInitial method is not getting called.</p>
  
  <pre><code>public HistoryPositionalDataSource(List&lt;CallTable&gt; callLogs)
  {
      this.callLogs = callLogs;
      Log.d("PaginationDataSource", "Constructor");
  }
  
  @Override
  public void loadInitial(@NonNull LoadInitialParams params, @NonNull LoadInitialCallback callback) {
      Log.d("PaginationDataSource", "loadInitial");
      if (callLogs!=null &amp;&amp; !callLogs.isEmpty())
      {
          int totalCount = computeCount();
          int position = computeInitialLoadPosition(params, totalCount);
          int loadSize = computeInitialLoadSize(params, position, totalCount);
          callback.onResult(loadRangeInternal(position, loadSize), position, totalCount);
      }
  }
  
  @Override
  public void loadRange(@NonNull LoadRangeParams params, @NonNull LoadRangeCallback callback) {
      callback.onResult(loadRangeInternal(params.startPosition, params.loadSize));
  }
  </code></pre>
  
  <p>Here's my PageListConfig</p>
  
  <pre><code>private void init() {
      pagedListConfig = (new PagedList.Config.Builder()).setEnablePlaceholders(true)
              .setInitialLoadSizeHint(Integer.MAX_VALUE).setPageSize(Integer.MAX_VALUE).build();
      Executor executor = Executors.newFixedThreadPool(3);
      List&lt;CallTable&gt; listLogs = getCallLogs(context);
      historyDataSourceFactory = new HistoryDataSourceFactory(listLogs);
      LivePagedListBuilder livePagedListBuilder = new LivePagedListBuilder(historyDataSourceFactory, pagedListConfig);
      pagedCallLogs =  livePagedListBuilder
              .setFetchExecutor(executor)
              .build();
  }
  </code></pre>
  
  <p>Factory class:</p>
  
  <pre><code>public class HistoryDataSourceFactory extends DataSource.Factory {
  
  private static final String TAG = HistoryDataSourceFactory.class.getSimpleName();
  private HistoryPositionalDataSource historyPositionalDataSource;
  
  public HistoryDataSourceFactory(List&lt;CallTable&gt; callLogs)
  {
      if (callLogs!=null &amp;&amp; !callLogs.isEmpty())
      {
          Log.d("PaginationFactory", "NotNullLogs");
          historyPositionalDataSource = new HistoryPositionalDataSource(callLogs);
      }
  }
  
  @Override
  public DataSource create() {
      return historyPositionalDataSource;
  }
  }
  </code></pre>
  
  <p>My getPagedCallLogs method:</p>
  
  <pre><code>public synchronized LiveData&lt;PagedList&lt;CallTable&gt;&gt; getPagedCallLogs() {
  
      if (pagedCallLogs!=null &amp;&amp; pagedCallLogs.getValue()!=null)
      {
          Log.d("PagingGetData", "Done");
          return pagedCallLogs;
      }
      else
      {
          Log.d("PagingGetData", "Null");
          return null;
      }
  }
  </code></pre>
  
  <p>Logs image is given below.
  <img src="https://i.imgur.com/ZWCogvH.jpg" alt="Logs"></p>