code: @Override
      protected void onDataChanged() {
          super.onDataChanged();
  
          int currentAngle = 0;
          int index = 0;
          int size = mPieData.size();
  
          for (PieModel model : mPieData) {
              int endAngle = (int) (currentAngle + model.getValue() * 360.f / mTotalValue);
              if(index == size-1) {
                  endAngle = 360;
              }
  
              model.setStartAngle(currentAngle);
              model.setEndAngle(endAngle);
              currentAngle = model.getEndAngle();
              index++;
          }
          calcCurrentItem();
          onScrollFinished();
      }
docs: Should be called after new data is inserted. Will be automatically called, when the view dimensions
  has changed.
  
  Calculates the start- and end-angles for every PieSlice.