ViewPager Fragments – onPageSelected/onPageUnSelected

Sometimes we need to know when fragment is selected and to handle it.

1. Add interface:

    public interface FragmentSelection{
        void onPageUnSelected();
        void onPageSelected();
    }

2. Implement this interface in your fragments:

public class YourFragment extends Fragment 
        implements SetScrollingActivity.FragmentSelection {

...

    @Override
    public void onPageUnSelected() {
        //
    }

    @Override
    public void onPageSelected() {
       //
    }

3. Add ‘setOnPageChangeListener’ on yours ViewPager instance

mViewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
    @Override
    public void onPageScrolled(int position, float positionOffset, 
            int positionOffsetPixels) {
    }

    @Override
    public void onPageSelected(int newPosition) {
          FragmentSelection fragmentToShow = (FragmentSelection) 
                  mSetScrollingAdapter.instantiateItem(mViewPager, newPosition);
          fragmentToShow.onPageSelected();

          FragmentSelection fragmentToHide = (FragmentSelection) 
                  mSetScrollingAdapter.instantiateItem(mViewPager, currentPosition);
          fragmentToHide.onPageUnSelected();

          currentPosition = newPosition;
    }

    @Override
    public void onPageScrollStateChanged(int state) {
    }
});