private void setCurrentPageImmediate() {
    if (viewPager != null) {
      currentPage = viewPager.getCurrentItem();
    } else {
      currentPage = 0;
    }

    if (pageCount > 0) {
      selectedDotX = dotCenterX[currentPage];
    }
  }
As this class <b>must</b> act as the {@link ViewPager.OnPageChangeListener} for the ViewPager
(as set by {@link #setViewPager(android.support.v4.view.ViewPager)}).  Applications may set a
listener here to be notified of the ViewPager events.

@param onPageChangeListener
java/com/google/android/apps/authenticator/howitworks/PagingIndicator.java