setOnPageChangeListener

When I change of fragment, always return position 0.

```
mViewPager.setAdapter(new FragmentPagerAdapter(getSupportFragmentManager()) {
@Override
public Fragment getItem(int position) {
switch (position) {
case 0:
return mHistoryFragment;
case 1:
return mPostFragment;
default:
return null;
}
}

@Override
public int getCount() {
return 2;
}
});

mViewPager.setPageMargin(8); // TODO Convert 'px' to 'dp'
mViewPager.setPageMarginDrawable(R.color.accent);

mTabsAction.setViewPager(mViewPager);
mTabsAction.setTitles(getString(R.string.button_new_history), getString(R.string.button_new_post));
//mTabsAction.setTabIndex(0, true);
mTabsAction.setStripColor(getResources().getColor(R.color.accent));
mTabsAction.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

}

@Override
public void onPageSelected(int position) {
validateButton();
switch (position) {
case 0:
TAB = HISTORY;
validateDraft(Constants.HISTORY);
break;
case 1:
TAB = POST;
validateDraft(Constants.POST);
break;
}
}

@Override
public void onPageScrollStateChanged(int state) {

}
});

mTabsAction.setOnTabStripSelectedIndexListener(new NavigationTabStrip.OnTabStripSelectedIndexListener() {
@Override
public void onStartTabSelected(String title, int index) {
validateButton();
switch (index) {
case 0:
TAB = HISTORY;
validateDraft(Constants.HISTORY);
break;
case 1:
TAB = POST;
validateDraft(Constants.POST);
break;
}
}

@Override
public void onEndTabSelected(String title, int index) {

}
});
```

thanks