code: private boolean showInitialFragment(@Nullable final String initialFragment) {
          if (!TextUtils.isEmpty(initialFragment)) {
              for (int i = 0; i < navigationFragment.getNavigationPreferenceCount(); i++) {
                  NavigationPreference navigationPreference =
                          navigationFragment.getNavigationPreference(i);
  
                  if (navigationPreference != null && navigationPreference.getFragment() != null &&
                          navigationPreference.getFragment().equals(initialFragment)) {
                      Bundle arguments = getIntent().getBundleExtra(EXTRA_SHOW_FRAGMENT_ARGUMENTS);
                      CharSequence title =
                              getCharSequenceFromIntent(getIntent(), EXTRA_SHOW_FRAGMENT_TITLE);
  
                      if (title != null) {
                          if (arguments == null) {
                              arguments = new Bundle();
                          }
  
                          arguments.putCharSequence(EXTRA_SHOW_FRAGMENT_TITLE, title);
                      }
  
                      navigationFragment.selectNavigationPreference(i, arguments);
                      return true;
                  }
              }
          }
  
          return false;
      }
docs: Initially displays a specific fragment.
  
  @param initialFragment
  The fully classified class name of the preference fragment, which should be shown, as
  a {@link String} or null, if no fragment should be initially shown
  @return True, if a fragment has been shown, false otherwise