code: @Override
      public void onItemSelected(int id) {
          if (mTwoPane) {
              // In two-pane mode, show the detail view in this activity by
              // adding or replacing the detail fragment using a
              // fragment transaction.
              Bundle arguments = new Bundle();
              arguments.putInt(ItemDetailFragment.ARG_ITEM_ID, id);
              ItemDetailFragment fragment = new ItemDetailFragment();
              fragment.setArguments(arguments);
              getSupportFragmentManager().beginTransaction()
              .replace(R.id.item_detail_container, fragment)
              .commit();
          } else {
              // In single-pane mode, simply start the detail activity
              // for the selected item ID.
              Intent detailIntent = new Intent(this, ItemDetailActivity.class);
              detailIntent.putExtra(ItemDetailFragment.ARG_ITEM_ID, id);
              startActivity(detailIntent);
          }
      }
docs: Callback method from {@link ItemListFragment.Callbacks} indicating that
  the item with the given ID was selected.