title: Android ViewPager's onPageScrollStateChanged never gets called
body: <p>I have extended the ViewPager class and implemented onPageChangeListener.
  I use this ViewPager in conjunction with a CirclePageIndicator inside a SherlockFragment. The ViewPager contains ImageViews and TextViews, nothing fancy.</p>
  
  <p>I need to do something below the ViewPager every time the Page is being changed. So, I figured I need to use the onPageScrollStateChanged and verify when the state is  IDLE, or something.</p>
  
  <p>The problem is that from the 3 implemented methods (onPageScrollStateChanged, onPageSelected and onPageScrolled), only onPageScrolled gets called (I checked with a log message in each method). Why is that ? Code below.</p>
  
  <pre><code>public class UninterceptableViewPager extends ViewPager implements OnPageChangeListener{
  
  private ArrayList&lt;TwoRowListViewAdapter&gt; mAdaptersList = null;
  private ListView mListView = null;
  private ProgressBar mProgressBar = null;
  
  
  public UninterceptableViewPager(Context context, AttributeSet attrs)
  {
      super(context, attrs);
  }
  
  public boolean onInterceptTouchEvent(MotionEvent event)
  {
      getParent().requestDisallowInterceptTouchEvent(true);
      return super.onInterceptTouchEvent(event);
  }
  
  
  public void setAdaptersList(ArrayList&lt;TwoRowListViewAdapter&gt; adaptersList)
  {
      mAdaptersList = adaptersList;
  }
  
  @Override
  public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels)
  {
      super.onPageScrolled(position++, positionOffset, positionOffsetPixels);
      if (positionOffset == 0) // FIXME
          loadHistoryPage(position);
  }
  
  @Override
  public void onPageSelected(int position) {}
  
  @Override
  public void onPageScrollStateChanged(int state) {}
  
  
  // -------------------------------------------------------------------------------------------
  // --------------   Helper Methods
  // -------------------------------------------------------------------------------------------
  
  
  public void setListView(ListView listview)
  {
      mListView = listview;
  }
  
  public void setProgressBar(ProgressBar progressBar)
  {
      mProgressBar = progressBar;
  }
  
  private void loadHistoryPage(int position)
  {
      mListView.setVisibility(View.INVISIBLE);
      mProgressBar.setVisibility(View.VISIBLE);
      mListView.setAdapter(null);
      mListView.setAdapter(mAdaptersList.get(position-1));
      mProgressBar.setVisibility(View.INVISIBLE);
      mListView.setVisibility(View.VISIBLE);
  }
  </code></pre>
  
  <p>}</p>