code: public void addPieSlice(PieModel _Slice) {
          highlightSlice(_Slice);
          mPieData.add(_Slice);
          mTotalValue += _Slice.getValue();
          onDataChanged();
      }
docs: Adds a new Pie Slice to the PieChart. After inserting and calculation of the highlighting color
  a complete recalculation is initiated.
  
  @param _Slice The newly added PieSlice.