title: OnpageScrolled is working twice in Viewpager
body: <p>I have a <code>ViewPager</code> which have contains two different fragments.
  We assume that they names are A and B fragments.
  One of these fragments has a date validation process. When a user attempts to navigate to B from A, if the selected date is later than today, the ViewPager turns back to Fragment A (rejecting navigation to B).</p>
  
  <p>This is provided with onPageScrolled like below.</p>
  
  <pre><code>@Override
      public void onPageScrolled( int position, float positionOffset, int positionOffsetPixels ) {
  
          if ( position == 0 ) {
              if (  positionOffset &gt; 0.5 &amp;&amp; getLastCycleDay() &gt; DateHelper.CreateToday( false ) ) {
                  mPager.setCurrentItem( 1 );
                  SnackbarHelper.newInstance().snackbarshow( IntroActivity.this, resources.getString( R.string.dont_allow_new_cycle ) );
              }
  
      }
  </code></pre>
  
  <p>My question is which <code>onPageScrolled</code> works twice and when I want to run a method in that, this method also works twice. </p>
  
  <p>How can I prevent this situation ?</p>