code: @Override
      public void draw(Canvas pCanvas, MilestoneStep pStep) {
          if (mFirst) {
              mFirst = false;
          } else {
              mLineDrawer.add(pStep.getX(), pStep.getY());
          }
          mLineDrawer.add(pStep.getX(), pStep.getY());
      }
docs: Overriding the "standard" milestone behavior (where we display something at each milestone)
  Instead, we populate a line drawer that will connect the steps