add comments in the navigation on the statistics fragment

src/de/tudarmstadt/informatik/hostage/ui2/fragment/StatisticsFragment.java

@@ -1815,19 +1815,28 @@ public class StatisticsFragment extends Fragment implements ChecklistDialog.Chec
      */
     private void pushRecordOverviewForFilter(LogFilter filter, String groupingKey){
 
+        // Get the FragmentManager from the MainActivity.
+        // The FragmentManager handles every pushing / popping action of a Fragment.
         FragmentManager fm = this.getActivity().getFragmentManager();
 
         if (fm != null){
+            // Create a new instance of your Fragment.
             RecordOverviewFragment newFragment = new RecordOverviewFragment();
+            // Set true, if the user can navigate backwards from the new pushed fragment.
 	        newFragment.setUpNavigatible(true);
-            newFragment.setFilter(filter);
 
+            // Set a Filter Object if needed.
+            // Otherwise the RecordOverviewFragment will display all possible records / attacks.
+            // With the filter object you also can change the sorting, by changing the sorttype of it.
+            if (filter != null) newFragment.setFilter(filter);
+
+            // Set a grouping key, if you want a other grouping behaviour than the default (timestamp).
             if (groupingKey != null && groupingKey.length() != 0) newFragment.setGroupKey(groupingKey);
 
+            // Push new Fragment
             MainActivity.getInstance().injectFragment(newFragment);
 
         }
-
     }