code: public boolean onLongClick(int index, boolean selectItem) {
          if (mLastLongPressIndex == null) {
              // we only consider long presses on not selected items
              if (mFastAdapter.getAdapterItem(index).isSelectable()) {
                  mLastLongPressIndex = index;
                  // we select this item as well
                  if (selectItem)
                      mFastAdapter.select(index);
                  if (mActionModeHelper != null)
                      mActionModeHelper.checkActionMode(null); // works with null as well, as the ActionMode is active for sure!
                  return true;
              }
          } else if (mLastLongPressIndex != index) {
              // select all items in the range between the two long clicks
              selectRange(mLastLongPressIndex, index, true);
              // reset the index
              mLastLongPressIndex = null;
          }
          return false;
      }
docs: will take care to save the long pressed index
  or to select all items in the range between the current long pressed item and the last long pressed item
  
  @param index the index of the long pressed item
  @param selectItem true, if the item at the index should be selected, false if this was already done outside of this helper or is not desired
  @return true, if the long press was handled