code: public void setDefaultIndicatorShape(Shape shape){
          if(mUserSetSelectedIndicatorResId == 0){
              if(shape == Shape.Oval){
                  mSelectedGradientDrawable.setShape(GradientDrawable.OVAL);
              }else{
                  mSelectedGradientDrawable.setShape(GradientDrawable.RECTANGLE);
              }
          }
          if(mUserSetUnSelectedIndicatorResId == 0){
              if(shape == Shape.Oval){
                  mUnSelectedGradientDrawable.setShape(GradientDrawable.OVAL);
              }else{
                  mUnSelectedGradientDrawable.setShape(GradientDrawable.RECTANGLE);
              }
          }
          resetDrawable();
      }
docs: if you are using the default indicator, this method will help you to set the shape of
  indicator, there are two kind of shapes you  can set, oval and rect.
  @param shape