code: public void setChartRotation(int rotation, boolean isAnimated) {
          if (isAnimated) {
              rotationAnimator.cancelAnimation();
              rotationAnimator.startAnimation(pieChartRenderer.getChartRotation(), rotation);
          } else {
              pieChartRenderer.setChartRotation(rotation);
          }
          ViewCompat.postInvalidateOnAnimation(this);
      }
docs: Set pie chart rotation. Don't confuse with {@link View#getRotation()}.
  
  @param rotation
  @see #getChartRotation()